close

Вход

Забыли?

вход по аккаунту

?

Farming and adiposity in Samoan adults.

код для вставкиСкачать
AMERICAN JOURNAL OF HUMAN BIOLOGY 18:112–122 (2006)
Original Research Article
Farming and Adiposity in Samoan Adults
EMBER D. KEIGHLEY,1 STEPHEN T. MCGARVEY,1* PASA TURITURI,2 AND SATUPAITEA VIALI3
1
International Health Institute, Department of Community Health, Brown University, Box G-B495,
Providence, Rhode Island
2
Diabetes Control Program, Department of Health, American Samoa Government, Pago Pago, American
Samoa 96799
3
Tupua Tamasese Meaole Hospital, Ministry of Health, Government of Samoa, Apia, Samoa
ABSTRACT
Samoans are experiencing some of the highest prevalences of obesity and associated health conditions in the world. Sustainable interventions are needed to prevent further
increases in obesity. This study describes the cross-sectional association between farm work and
adiposity among 754 adults residing in American Samoa in 2002 and 957 adults residing in Samoa
in 2003. Adiposity was measured by body mass index (BMI) and percent body fat (% BF), based on
bioelectrical impedance. Regression models adjusted for the effects of age, education, occupation
(in women), and material lifestyle (MLS), and the clustering within households due to the family
design of the parent study. After controlling for these variables, participation in farm work
was associated with a significantly lower BMI and % BF in men of all ages residing in American
Samoa, women 45 years residing in American Samoa, and women 18–44 years residing in
Samoa, and a significantly lower BMI in men 18–44 years residing in Samoa. These results
suggest that farm work plays an important role in regulating body size and fatness of adult
Samoans and may be ideal for interventions in the Samoan archipelago. Am. J. Hum. Biol.
# 2005 Wiley-Liss, Inc.
18:112–122, 2006.
Over the past one hundred years, modernization has had profound effects on the way
of life, biology and health of Samoans (Baker
et al., 1986). Obesity and its associated
health conditions have reached prevalences
among the highest in the world and appear
to have continued steadily increasing
through the last three decades (Keighley et
al., 2006; McGarvey, 1991, 2001). Between
1976 and 2003 in both American Samoa
and Samoa there were sharp increases in
the prevalence of obesity, defined here as a
BMI > 32 kg/m2, based on body composition
studies among Polynesians (Swinburn et al.,
1999). Among men, 25–74 years, living in
American Samoa, 32.2% were obese in
1976, while 63.1% were obese by 2002
(Keighley et al., 2006). Among women living
in American Samoa the prevalence of obesity
increased from an already high 58.0% in
1976 to 75.0% in 2002. While the prevalence
of obesity is considerably lower among residents of Samoa (formerly Western Samoa), it
also increased rapidly over the past 30 years.
Between 1979 and 1982, 10.8% of men and
31.5% of women were obese but by 2003,
34.1% of men and 58.7% of women were
obese.
ß 2005 Wiley-Liss, Inc.
Furthermore, there were temporal
increases in the mean BMI and the proportion of those within the highest BMI classes.
In American Samoa, between 1976 and 2002,
the percent of men, 25–74 years, with BMI 40 kg/m2 almost tripled, from 5.0% to 14.4%,
and the percent of women more than
doubled, reaching 32.8%. Among adults
residing in Samoa, the percent of people
with BMI 40 kg/m2 has risen sharply
from 1.8% of men and 3.8% of women in
1979–1982 to 6.8% and 15.9% respectively
in 2003. Longitudinal data also indicate
that despite pre-existing excess adiposity,
Samoans are able to continue to gain weight
(McGarvey, 1991).
Contract grant sponsor: NIH; Contract grant number:
DK59642; Contract grant sponsor: Brown University
Undergraduate Teaching and Research Assistantship.
*Correspondence to: Stephen T. McGarvey, Ph.D.,
M.P.H., International Health Institute, Brown University,
Box G-B495, Providence, RI 02912. E-mail: Stephen_
McGarvey@brown.edu
Received 29 June 2005; Revision received 16 September
2005; Accepted 27 September 2005
Published online in Wiley InterScience (www.interscience.
wiley.com). DOI: 10.1002/ajhb.20469
113
FARMING AND ADIPOSITY IN SAMOAN ADULTS
Samoans are not alone in this rapid nutrition and health transition. Throughout the
Pacific, obesity has become widespread.
Currently 8–10% of all deaths in the Pacific
region are attributable to obesity (WHO,
2000). These trends are ultimately due to
the economic, social and nutritional changes
in the Pacific, but may be interacting with
a putative increased susceptibility to obesity among Polynesians (McGarvey, 1994;
McGarvey et al., 1989). As the Pacific islands
rapidly modernize, it is crucial that we find
effective means of avoiding obesity and
implement interventions to help prevent
further increases in adiposity.
Farm work is a traditional subsistence
activity for both men and women throughout
the Samoan archipelago (Greksa et al.,
1986). In American Samoa, participation in
farm work has decreased dramatically in the
last 40 years. On Tutuila, the main island of
American Samoa, the primary occupation
among adult males in 1960 was agriculture,
but by 1974 only 8% of economically active
males were still involved in plantation work
(Greksa and Baker, 1982). According to the
American Samoa 1990 census 3% of all
adults and in the 2000 census 7% of all
adults in American Samoa did primarily subsistence work (U.S. Department of
Commerce, 1992, 2004). In Samoa, over
time, professional and less physically
demanding occupations have increased. In
the 1991 census, among adults 24% of men
and 14% of women worked in wage or salary
jobs (Western Samoan Department of
Statistics, 1995). In 1991, 67% of men and
63% of women in the economically active
group still worked primarily in subsistence
farming and fishing. By the 2001 census in
Samoa, 44% of men in the economically
active group were engaged primarily in subsistence work (Samoa Department of
Statistics, 2003).
The shift away from agriculture may have
a 2-fold impact on the health of Samoans.
First, people may be less physically active.
On average agriculture requires a 65-kg
Samoan man to expend 6–7 kcal/min
(Greksa and Baker, 1982). In contrast, office
employees only expend 1.7–1.9 kcal/min. A
1982 study in Samoa found greater energy
expenditure and lower adiposity among
young rural men and active urban workers
compared to sedentary urban workers
(Pelletier, 1987). Second, people who are
not participating in farm work may experi-
ence a dietary shift decreasing the consumption of locally produced fruits and vegetables, and increasing the consumption of
imported processed foods. While the consumption of fat from imported foods
increases the risk of obesity by 2.2-fold and
diabetes by 2.4-fold, diets composed primarily of locally produced foods have been shown
to prevent and reduce obesity (WHO, 2003).
A 1990–1991 dietary study in American
Samoa and Samoa showed greater consumption of imported foods with increasing socioeconomic status regardless of residence
(Galanis et al., 1999).
Population variation in patterns of physical activity with the physical environment,
modes of subsistence and with economic
modernization has been described and
reviewed (Ulijaszek, 1995; Weitz et al.,
1989). A fuller multilevel exploration of the
impacts of modernization and urbanization
on occupational changes, work intensity,
dietary patterns and physical activity patterns remains an ambitious and crucial goal
for human population biology. Here we do
not focus on the ultimate and proximate factors that determine physical activity variations in modernizing Samoans, or an
exploration of the retention of the seemingly
‘‘traditional’’ physical activity, farm work.
That is one of our future objectives. In this
report we concentrate on the effect of a specific type of physical activity on adiposity
from a human biological and public health
perspective.
The purpose of this study is to examine the
cross-sectional association between farm
work and adiposity, measured by BMI and
percent body fat (% BF), in adult Samoans
residing in American Samoa in 2002 and
Samoa in 2003.
METHODS
The study population derives from the
U.S. territory of American Samoa and the
independent nation of Samoa (formerly
Western Samoa). In 2000, the population of
American Samoa was 57,291, of which 88.2%
are ethnic Samoans (U.S. Department of
Commerce 2004). The government offices
and tuna canneries in the Pago Pago harbor
offer many job opportunities in wage-labor.
In 2000 most adults, 52%, are employed in
the paid labor force, while only 6.7% of
adults participate primarily in subsistence
activities. In 2001, Samoa had a population
114
E.D. KEIGHLEY ET AL.
of 176,848 (Samoa Department of Statistics,
2003). Although Samoa is located just 100
km from American Samoa, fewer adults
hold wage-labor jobs and the economy is
largely based on agriculture, with tourism
becoming increasingly important (Western
Samoa Department of Statistics, 1995). In
1991, approximately 15% of adults of both
sexes were employed in wage-labor professions, but by 2001 36% of men and 26% of
women were in wage or salary jobs (Samoa
Department of Statistics, 2003).
All participants took part in the Samoan
Family Study of Overweight and Diabetes in
2002–2003. Protocols for this study
were approved by the Brown University
Institutional Review Board, American
Samoan Institutional Review Board, and
the Government of Samoa, Ministry of
Health, Health Research Committee.
Written informed consent was obtained
from all participants. Recruitment in
American Samoa in 2002 was based on random selection of probands seen in the 1990–
1994 cohort study in American Samoa, and
the presence of at least two adult siblings
alive and residing in American Samoa.
Recruitment in Samoa in 2003 was first
based on finding named individuals residing
in Samoa who were members of American
Samoa pedigrees. After that short period of
4–6 weeks, we selected villages to represent
geographic and socioeconomic diversity
across the nation. Then, selection of families
was based on discussions with the village
leaders about the size of the families and
the presence of at least two adult siblings.
Participants were recruited based on availability of large extended families and probands were not selected for obesity or type
2 diabetes. Participants resided in a range of
rural to urban villages in both Samoa and
American Samoa and had varying degrees of
education, occupation and material way of
life (Table 1). Participants were classified
into two age groups: 18–44 years and 45
years and above. All data analyses were stratified by nation and sex.
Participants were assigned to the farm
work or no farm work group based on selfreported participation in farm work, and/or
self-reported subsistence work as their primary occupation. Farm work was used as a
dichotomous variable.
Measurements of stature and weight were
taken with participants wearing light tropical clothing, and BMI was calculated.
Impedance measures of participants were
taken with the Quantum II Bioelectrical
Body Composition Analyzer. Percent body
fat (% BF) was calculated using resistance
in the equation developed by Swinburn et
al. (1999) for use in Polynesians. We discovered that this equation contained a mistake
in publication and after communication with
the author we used the following correct
equation: Fat Mass ¼ 11.58 þ 0.79(weight)
0.15(height) þ 0.04(age) 6.0(sex) 0.39
(height2/resistance), where weight is measured in kg, height in cm (instead of m as
previously reported), age in years, resistance
in ohms, and sex ¼ 1 for males and sex ¼ 0
for females. Swinburn et al. (1999) developed
this equation for Polynesians between the
ages of 20 and 70 years, but here we
extended this age range to 18–90 years.
While it is not ideal to extend the age
range, we believe that this is the best equation available for measuring body fat in
Polynesian adults. All % BF results from
the Swinburn et al. (1999) equation when
applied to the extended age-range were
cross-validated with % BF estimated from
equations developed specifically for multiethnic U.S. adolescent girls (Philips et al.,
2003), Polynesian adolescents (Rush et al.,
2003), and European elderly (Dey and
Bosaeus, 2003). The % BF results from the
different equations were quite similar and
are available upon request.
Education was classified into two groups:
less than secondary education and secondary education and above. In American
Samoa, where schools are run on a U.S.based system, secondary education is the
equivalent of 12 years of education. In
Samoa, the schools use a New Zealand system and secondary education is equivalent
to 13 years.
Occupation was divided into three categories: unemployed (including housewives
and retirees), subsistence work (farming
and fishing), and non-subsistence work
(including wage-labor occupations and traditional village leadership). Those reporting
two jobs were assigned the occupation with
a higher socioeconomic status. For example,
people reporting both a wage-labor occupation and farm work were assigned the wagelabor occupation.
Material lifestyle (MLS) was defined using
a 10-point index (Galanis et al., 1999). The
index was based on ownership of amenities
including: flooring, refrigerator, stereo, TV,
115
FARMING AND ADIPOSITY IN SAMOAN ADULTS
TABLE 1. Descriptive statistics of the study sample
Education
Less than
secondary
% n/N
Men in American Samoa,
18–44 years
13.4%
27/201
Men in American Samoa,
45þ years
34.7%
43/124
Women in American Samoa,
18–44 years
9.2%
24/262
Women in American Samoa,
45þ years
38.7%
55/142
Men in Samoa,
18–44 years
74.0%
188/254
Men in Samoa,
45þ years
90.0%
162/180
Women in Samoa,
18–44 years
70.5%
208/295
Women in Samoa,
45þ years
90.0%
199/221
Material
lifestyle
Occupation
Secondary
% n/N
Unemployed
% n/N
Subsistence
work
% n/N
Non-subsistence
work
% n/N
Low
% n/N
High
% n/N
86.6%
174/201
9.8%
18/183
4.9%
9/183
85.2%
156/183
36.5%
72/197
63.5%
125/197
65.3%
81/124
48.7%
58/119
5.0%
6/119
46.2%
55/119
44.0%
55/125
56.0%
70/125
90.8%
238/262
43.0%
107/249
–
57.0%
142/249
39.6%
106/268
60.4%
162/268
61.3%
87/142
71.4%
100/140
–
28.6%
40/140
37.4%
55/147
62.6%
92/147
26.0%
66/254
8.6%
22/255
64.3%
164/255
27.1%
69/255
55.3%
140/253
44.7%
113/253
10.0%
18/180
17.0%
31/182
63.7%
116/182
19.2%
35/182
68.3%
123/180
31.7%
57/180
29.5%
87/295
75.8%
225/297
0.3%
1/297
23.9%
71/297
56.7%
165/291
43.3%
126/291
10.0%
22/221
91.0%
202/222
0.9%
2/222
8.1%
18/222
62.2%
138/222
37.8%
84/222
VCR, vehicle, electricity, stove toilet, and
drinking water. Only people who completed
at least 7 out of 10 questions were given a
score. Any missing values for these people
were imputed based on the average for
their nation, sex, and 10-year age group.
Those who scored an 8 or higher were
assigned relative high MLS while those
with less than an 8 were assigned relative
low MLS.
Whenever possible, household was defined
as the fale, house, where participants resided at time of measurement. In American
Samoa, household was determined by the
telephone number and by families living in
the same village when there was no phone.
In Samoa, household was defined by each
participant’s reported fale when data was
available and by families living in the same
village when no individual household information was available.
Bivariate analysis between farm work and
education, MLS, and occupation were done
with categorical methods. Multivariate analysis of BMI, % BF, and farm work were done
with general linear models. Education, occupation, and MLS were controlled for as confounders. We adjusted for household
clustering due to the participation of individuals from the same house, which violates
the assumption of independence of observations. Age was controlled for in all analyzes
with BMI and % BF. All analyzes were done
using SPSS.
RESULTS
The study sample includes 332 men and
422 women from American Samoa and 438
men and 519 women from Samoa between
the ages of 18 and 90 years (Table 2).
Participants lived in 426 separate house-
116
E.D. KEIGHLEY ET AL.
TABLE 2. Percent of people participating in farm work and average number of hours per week spent on the farm
American Samoa
Males
Females
Age (years)
n/N
%
18–44
45þ
Total
18–44
45þ
Total
101/204
67/128
168/332
58/271
36/151
94/422
49.5%
52.3%
50.6%
21.4%
23.8%
22.3%
Samoa
X (SD) (h/week)
4.1
4.4
4.2
4.1
2.6
3.5
(4.2)
(5.1)
(4.6)
(5.4)
(1.9)
(4.5)
n/N
%
X (SD) (h/week)
215/256
150/182
365/438
91/297
67/222
158/519
84.0%
82.4%
83.3%
30.6%
30.2%
30.4%
8.1
6.7
7.5
3.3
3.9
3.6
(8.8)
(8.4)
(8.7)
(3.5)
(5.5)
(4.4)
TABLE 3. Mean BMI and % BF of the study sample
American Samoa
2
Age (years)
Males
18–44
45þ
Females
18–44
45þ
Samoa
2
BMI (kg/m )
n X (sd)
%BF
n X (sd)
BMI (kg/m )
n X (sd)
%BF
n X (sd)
n ¼ 204
33.3 (7.5)
n ¼ 128
33.7 (7.3)
n ¼ 271
36.7 (8.3)
n ¼ 151
36.2 (8.1)
n ¼ 204
32.8 (7.2)
n ¼ 128
34.8 (5.9)
n ¼ 271
41.1 (6.5)
n ¼ 151
42.2 (6.1)
n ¼ 256
27.9 (5.0)
n ¼ 182
31.5 (5.8)
n ¼ 297
32.0 (6.7)
n ¼ 222
34.0 (7.7)
n ¼ 152
26.0 (6.4)
n ¼ 95
33.3 (6.3)
n ¼ 150
37.6 (6.9)
n ¼ 125
40.7 (6.2)
holds: 201 in American Samoa and 225 in
Samoa. The study sample is marked by
high levels of BMI and % BF (Table 3). In
American Samoa, mean BMI for both men
and women is above the Polynesian criteria
for obesity. Percent body fat ranges from
32.8% to 34.8% in men and 41.1% to 42.2%
in women. In Samoa, mean BMI is significantly lower than in American Samoa for all
age and sex groups. Percent body fat in
Samoa ranges from 26.0% to 33.3% in men
and 37.6% to 40.7% in women.
About 50% of men in American Samoa and
over 80% of men in Samoa participate in
farm work (Table 2). Fewer women, 22% in
American Samoa and 30% in Samoa, participate in farm work. Young men and women
from American Samoa, 18–44 years, spend
about 4 h per week doing farm work (Table 2).
In Samoa, young men spend twice as much
time working on the farm, 8.1 h, and young
women spend slightly less, 3.3 h. In
American Samoa, older men, 45 and above,
spend more time per week on the farm than
their younger counterparts, 4.4 h, and older
women spend the least time on the farm, 2.6
h. In Samoa, older men continue to spend
considerable time on the farm, 6.7 h, and
older women spend more time than the
younger age group, 3.9 h. Most of the groups
sampled here average above the recommended minimum number of hours of physical activity per week, 30 min daily (WHO,
2005), on the farm, with the exception of
older women in American Samoa and youn
ger women in Samoa.
The study sample in American Samoa is
characterized by high levels of education,
especially among the younger age group
where 86.6% of men and 90.8% of women
completed a secondary education or above
(Table 1). In American Samoa, the majority
of young men and women have non-subsistence occupations, while almost 50% of men
and over 70% of women 45 and above are
unemployed or retired. The majority of men
and women in all age groups in American
Samoa have a relatively high material lifestyle status.
In Samoa, the study sample is characterized by comparatively lower levels of education than in American Samoa (Table 1). Less
than 30% of younger men and women and
only 10% of older men and women completed
a secondary education or above. The majority of men in Samoa perform subsistence
work as their primary occupation, while the
majority of women are unemployed. Most
men and women in Samoa have a relatively
low material lifestyle status.
117
FARMING AND ADIPOSITY IN SAMOAN ADULTS
Among men of all ages from American
Samoa, older women from American Samoa,
and older men and women from Samoa, there
are no significant differences in education level
between the farm work and no farm work
groups. While among young women from
American Samoa, and young men and women
from Samoa, those who participate in farm
work are less likely to have completed a secondary or higher education (P ¼ 0.043, 0.038,
and 0.030, respectively). Men of all ages from
American Samoa and all men and women from
Samoa show significant differences in occupation between the farm work and no farm work
groups. This is primarily due to people who
report participating in subsistence work all
being in the farm work group. Men from
American Samoa and Samoa, and older
women from Samoa who participate in farm
work are less likely to report being unemployed. Younger women from Samoa who participate in farm work are more likely to report
being unemployed. Among women from
American Samoa, there are no significant differences in occupation in the farm work group.
There are no significant differences in material
lifestyle between the farm work and no farm
work groups in either polity.
Education level alone is not significantly
related to BMI or % BF in either nation or
sex. Occupation is only directly related to
BMI in older men from American Samoa (P
¼ 0.041). Those men who are unemployed
have an average BMI of 35.7 kg/m2 compared
to 32.1 kg/m2 in those who participate in
subsistence work as their primary occupation, and 32.2 kg/m2 in the employed group.
Occupation is not directly related to % BF in
either nation or gender. MLS is significantly
related to BMI in younger men and older
women from American Samoa, as well as
younger men from Samoa (P < 0.001, P ¼
0.003, P ¼ 0.001, respectively). In each of
these age groups, being in the higher MLS
category is associated with an increase in
BMI of 1.8–4.0 kg/m2. MLS is also significantly related to % BF in the same groups
(P ¼ 0.004, P ¼ 0.010, P ¼ 0.015, respectively), with an increase in average % BF in
the higher MLS group.
Farm work is significantly associated with
a lower age-adjusted BMI in men and older
women from American Samoa, as well as
young men and young women residing in
Samoa (Table 4). Within these groups,
those who participate in farm work have
age-adjusted BMI 2.0–3.6 kg/m2 lower than
those who do not participate. Farm work is
also significantly associated with a lower %
BF in men and older women living in
American Samoa, as well as younger
women living in Samoa (Table 5).
To measure the direct effect of farm work
on BMI, in women multivariable analyses
were done controlling for age, education,
MLS, household, and occupation, and in
men analyses were done controlling for age,
education, MLS, and household. A large
number of men reported subsistence work
as their primary occupation. Therefore, multivariable models in men that adjust for
occupation would lead to over-controlling
for the effect of farm work on adiposity.
This is not a problem in women because
few women report subsistence work as their
primary occupation.
In the multivariable models with adjustments for age, education, MLS, and occupation (in women), participation in farm work
is significantly associated with reduced BMI
TABLE 4. Association between farm work and BMI (in kg/m2) in adults*
American Samoa
Age (years)
Male
18–44
45þ
Female
18–44
45þ
Mean (SEM) N
No farm work
Farm work
No farm work
Farm work
No farm work
Farm work
No farm work
Farm work
*Controlling for age; NS, nonsignificant.
34.7
32.0
35.4
32.2
36.9
35.9
37.1
33.5
(0.7)
(0.7)
(0.9)
(0.8)
(0.6)
(1.1)
(0.7)
(1.3)
N
N
N
N
N
N
N
N
¼
¼
¼
¼
¼
¼
¼
¼
103
101
61
67
213
58
115
36
Samoa
t
P
6.9
0.009
7.1
0.009
0.7
NS
5.9
0.017
Mean (SEM) N
29.5
27.5
31.8
31.4
32.7
30.4
34.1
34.0
(0.7)
(0.3)
(1.0)
(0.5)
(0.4)
(0.6)
(0.6)
(1.0)
N
N
N
N
N
N
N
N
¼
¼
¼
¼
¼
¼
¼
¼
41
215
32
150
206
91
155
67
t
P
6.8
0.010
0.2
NS
9.2
0.003
<0.1
NS
118
E.D. KEIGHLEY ET AL.
TABLE 5. Association between farm work and % BF in adults*
American Samoa
Mean (SEM) N
Age (years)
Male
18–44
45þ
Female
18–44
45þ
No farm work
Farm work
No farm work
Farm work
No farm work
Farm work
No farm work
Farm work
34.5%
31.1%
36.4%
33.4%
41.3%
40.5%
42.9%
40.0%
(0.7)
(0.7)
(0.7)
(0.7)
(0.4)
(0.9)
(0.5)
(1.0)
N
N
N
N
N
N
N
N
¼
¼
¼
¼
¼
¼
¼
¼
103
101
61
67
212
57
115
36
Samoa
t
P
12.6
<0.001
8.6
0.004
0.6
6.7
NS
0.011
Mean (SEM) N
27.4%
25.7%
34.2%
33.0%
38.6%
35.5%
40.3%
41.5%
(1.1)
(0.5)
(1.5)
(0.7)
(0.6)
(0.8)
(0.7)
(1.0)
N
N
N
N
N
N
N
N
¼
¼
¼
¼
¼
¼
¼
¼
25
127
20
75
102
48
86
39
t
P
2.1
NS
0.5
NS
9.4
.003
0.9
NS
*Controlling for age; NS, nonsignificant.
and % BF in the same age and sex groups as
the age-adjusted results (Tables 6 and 7). In
young men from American Samoa, adjusted
mean BMI is 1.8 kg/m2 lower in the farm
work group, and % BF is 2.9% lower (Tables
6a and 7a). Older men from American Samoa
who participate in farm work have an
adjusted mean BMI 2.6 kg/m2 lower and an
adjusted mean body fat 2.9% lower (Tables 6a
and 7a). Older women from American Samoa
doing farm work have a BMI 4.9 kg/m2 lower
and a body fat 4.0% lower (Tables 6b and 7b).
There is not a significant association between
farm work and % BF in young men from
Samoa, but the mean adjusted BMI is 1.9
kg/m2 lower in the farm work group (Tables
6c and 7c). Among young women living in
Samoa, those who participate in farm work
have an average BMI 2.0 kg/m2 lower and a
body fat 3.0% lower (Tables 6d and 7d).
DISCUSSION
The results presented here show consistent cross-sectional evidence that farm
work is associated with lower BMI and %
BF among Samoan men and women living
throughout the Samoan archipelago. These
findings remain significant after adjusting
for household clustering, and the influences
of age, level of education, MLS, and occupation (in women). The results are consistent
with those found in an earlier cross-sectional comparison of physical activity and
adiposity among urban and rural men in
Samoa (Pelletier, 1987), as well as ecological
studies from Samoa and other Pacific
nations (Baker et al., 1986; Wessen et al.,
1992).
Our findings show a distinct age and gender pattern. It is not surprising that farm
work and BMI are related in young men
from American Samoa and young men and
women from Samoa. Within Samoan culture,
it is often the younger and untitled men and
women who perform the majority of the physical labor for the village (Greksa et al., 1986;
Mead, 1969; O’Meara, 1990). While young
women from American Samoa who participate in farm work also have a lower average
BMI and % BF, these results are not statistically significant. These young women from
American Samoa are participating in the
same number of hours of farm work as the
young men, but they may not be participating
in tasks that are as physically demanding.
While younger men and women are
responsible for the majority of the physical
farm labor, older men and women, especially
titled members of the village, often take
more managerial roles (O’Meara, 1990).
Despite these age patterns, it is noteworthy
that in American Samoa, older men and
women who continue to participate in farm
work also maintain a lower average BMI and
% BF. This may be due to the daily activity
from farm work, or it may be due to a lifetime effect of consistently living a more
active lifestyle and perhaps eating a diet
richer in fruits and vegetables.
For the over 50% of older men from
American Samoa who participate in farm
work, doing less than 1 h of work per day,
on average, is associated with a BMI 2.5 kg/
m2 lower, regardless of age, education, and
MLS (Tables 6a and 7a). Among women 45
and above from American Samoa, participating in as few as 2.6 h per week of farm work,
less than the recommended weekly minimum (WHO, 2005), is associated with a
decrease in BMI of 5.1 kg/m2 and a decrease
in body fat of 4.1%, after controlling for age,
119
FARMING AND ADIPOSITY IN SAMOAN ADULTS
TABLE 6. Results of linear models of farm work and BMI adjusted for age, education, occupation, and MLS
18–44 years
(a) Men in American Samoa
Age
Farm work
Education
Occupationa
MLS
Household
Adjusted means of BMI (SEM)
Farm work
No
Yes
(b) Women in American Samoa
Age
Farm work
Education
Occupation
MLS
Household
Adjusted means of BMI (SEM)
Farm work
No
Yes
(c) Men in Samoa
Age
Farm work
Education
Occupationa
MLS
Household
Adjusted means of BMI (SEM)
Farm work
No
Yes
(d) Women in Samoa
Age
Farm work
Education
Occupation
MLS
Household
Adjusted means of BMI (SEM)
Farm work
No
Yes
45þ years
F
P
F
P
16.6
4.2
0.4
—
11.1
1.4
<0.001
0.041*
0.531
—
0.001
0.237
12.1
5.7
0.7
—
0.5
0.4
0.001
0.019*
0.389
—
0.488
0.553
N ¼ 97
N ¼ 97
x ¼ 33.8 kg/m2 (0.6)
x ¼ 32.0 kg/m2 (0.6)
N ¼ 59
N ¼ 62
x ¼ 34.7 kg/m2 (0.8)
x ¼ 32.1 kg/m2 (0.8)
10.0
0.5
0.2
0.1
0.6
0.5
<0.002
0.485
0.696
0.805
0.447
0.502
8.4
10.6
0.1
1.2
10.3
1.0
0.004
0.001**
0.786
0.275
0.002
0.319
N ¼ 185
N ¼ 53
x ¼ 37.5 kg/m2 (0.6)
x ¼ 36.6 kg/m2 (1.2)
N ¼ 95
N ¼ 33
x ¼ 38.1 kg/m2 (0.8)
x ¼ 33.2 kg/m2 (1.3)
61.7
6.0
0.2
—
10.0
0.1
<0.001
0.015*
0.672
—
0.002
0.794
19.4
0.3
<0.1
—
2.7
0.1
<0.001
0.588
0.921
—
0.105
0.775
N ¼ 40
N ¼ 210
x ¼ 29.5 kg/m2 (0.7)
x ¼ 27.6 kg/m2 (0.3)
N ¼ 31
N ¼ 148
x ¼ 32.0 kg/m2 (1.0)
x ¼ 31.4 kg/m2 (.5)
63.0
6.6
0.5
0.6
<0.1
3.7
<0.001
0.010*
0.497
0.444
0.886
0.055
16.9
<0.1
0.6
0.2
1.0
0.6
<0.001
0.995
0.451
0.640
0.331
0.454
N ¼ 199
N ¼ 90
x ¼ 32.6 kg/m2 (0.4)
x ¼ 30.6 kg/m2 (0.6)
N ¼ 154
N ¼ 67
x ¼ 34.0 kg/m2 (0.6)
x ¼ 34.0 kg/m2 (1.0)
a
Occupation is left out due to over controlling (for men’s values only).
*For farmwork, P < 0.050.
**For farmwork, P < 0.010.
education, occupation, and MLS (Tables 6b
and 7b).
Levels of obesity among older women in
American Samoa are so high that participation in some form of physical activity, even if
it is only for a minimal amount of time each
week and at a lower intensity, appears to
influence adiposity. While those women
who do not participate in farm work have
an adjusted mean BMI in the range of class
II obesity, those women who do have an
adjusted mean BMI in the class I obesity
range. A decrease from class II to class I
obesity carries important health benefits,
including a decrease from severe to moderate risk of hypertension, type 2 diabetes, and
other aspects of metabolic syndrome (SPC,
2002). Furthermore, physical activity
increases insulin sensitivity and has been
shown to be effective in controlling type II
Diabetes (Barnard et al., 1994). Despite
these positive health benefits, less than 25%
of older women in American Samoa participate in farm work.
120
E.D. KEIGHLEY ET AL.
TABLE 7. Results of linear models of farm work and % BF adjusted for age, education, occupation, and MLS
18–44 years
(a) Men in American Samoa
Age
Farm work
Education
Occupationa
MLS
Household
Adjusted mean % BF (SEM)
Farm work
No
Yes
(b) Women in American Samoa
Age
Farm work
Education
Occupation
MLS
Household
Adjusted mean % BF (SEM)
Farm work
No
Yes
(c) Men in Samoa
Age
Farm work
Education
Occupationa
MLS
Household
Adjusted mean % BF (SEM)
Farm work
No
Yes
(d) Women in Samoa
Age
Farm work
Education
Occupation
MLS
Household
Adjusted mean % BF (SEM)
Farm work
No
Yes
45þ years
F
P
F
P
22.9
9.3
0.3
—
7.3
3.0
<0.001
0.003**
0.600
—
0.008
0.087
1.0
7.6
0.6
—
0.2
1.7
0.310
0.007**
0.456
—
0.665
0.189
N ¼ 97
N ¼ 97
x ¼ 34.0% (0.7)
x ¼ 31.1% (0.7)
N ¼ 59
N ¼ 62
x ¼ 36.2% (0.7)
x ¼ 33.3% (0.7)
0.001
0.593
0.850
0.373
0.159
0.790
4.0
12.3
<0.1
0.1
7.5
1.3
0.049
0.001**
0.882
0.720
0.007
0.262
x ¼ 41.7% (.5)
x ¼ 41.1% (.9)
N ¼ 95
N ¼ 33
x ¼ 43.5% (.6)
x ¼ 39.5% (1.0)
<0.001
0.250
0.486
—
0.015
0.257
4.6
1.7
0.4
—
0.3
<0.1
x ¼ 27.2% (1.1)
x ¼ 25.8% (0.5)
N ¼ 19
N ¼ 73
48.5
7.8
1.0
0.2
0.6
0.3
<0.001
0.006**
0.311
0.661
0.456
0.566
1.7
1.0
0.4
<0.1
0.4
3.1
N ¼ 97
N ¼ 48
x ¼ 38.6% (0.6)
x ¼ 35.6% (0.9)
N ¼ 85
N ¼ 39
10.6
0.3
<0.1
0.8
1.0
<0.1
N ¼ 184
N ¼ 53
42.7
1.3
0.5
—
6.0
1.3
N ¼ 24
N ¼ 123
0.034
0.200
0.540
—
0.559
0.879
x ¼ 35.0% (1.5)
x ¼ 32.9% (0.7)
0.200
0.311
0.533
0.971
0.530
0.083
x ¼ 40.3% (0.7)
x ¼ 41.6% (1.1)
a
Occupation is left out due to over controlling (for men’s values only).
*For farmwork, P < 0.050.
**For farmwork, P < 0.010.
These results have important human biological and applied public health implications. Because this study is part of genetic
epidemiologic research on determinants of
adiposity, the results indicate that we must
adjust for this type of physical activity as
part of the search to detect putative genetic
effects on Samoan adiposity. It also suggests
that we should consider gene-by-physical
activity analyses to determine if different
genetic factors are linked to adiposity
depending on levels of physical activity.
From a public health perspective, in a population with high prevalence of obesity, farming for less than 1 h per day appears to be
associated in both men and women with
some relative protection from reaching the
extreme levels of obesity of their nonfarming
peers. This difference remains after controlling for household, education, MLS, and
occupation (in women). These findings suggest that farm work intervention may be
FARMING AND ADIPOSITY IN SAMOAN ADULTS
feasible among adult residents of both
Samoan polities. An intervention could
have a profound impact on the levels of adiposity, even if it only engages people in minimal amounts of physical activity. Lowering
adiposity, especially among this older age
group, may have extensive health benefits
for the people and ease the burden of chronic
disease on the healthcare system.
Limitations and future directions
This study does not take into account
actual levels of physical activity. Such a
study measuring METS or some other
index of exercise intensity might provide
more ability to detect the direct effects of
physical activity from farm work on adiposity. We are currently developing such an
index. Future studies of the impact of farm
work on BMI and % BF should also incorporate measures of diet. Here we have not
explored if the impact of farm work on adiposity is due entirely to physical activity or if
it is confounded with variation in diet.
Controlling for the MLS categories we
created allows us to conclude that farm
work is not tied to income level at least
with the measure we used, although there
are certainly other methods of measuring
and categorizing income which may show
different results. Additionally, while controlling for household income suggests that
the relationship between farm work and
adiposity is not principally due to either
shared dietary intake or genetics (most
households contain two to three generations of family members and share meals),
future studies should look at dietary intake
and genetic effects.
Furthermore, there may be additional
issues of selectivity that we have not controlled for in our farm work group. Because
this is a cross-sectional study, we cannot
determine if the effect of farming, especially
in the older age group, is due primarily to the
direct effect of farming at the time of measurement and in the recent past, or if it is
due to a lifetime effect of participating in
physical activity from farming. It is possible
that older adults who have continued to
remain active are benefiting from a lifetime
of activity, and not just the daily energy
expenditure which they were participating
in when they were measured. If this older
age group is benefiting from lifetime effects
of participating in farm work, that would
121
suggest that in order to improve Samoans’
health it is most important to implement
intervention in younger age groups.
Otherwise, if the act of farming is beneficial
to older adults regardless of whether they
farmed continuously since childhood, then
implementing interventions in older adults
may also have important health benefits.
The findings also indicate the need for a
more detailed analysis of the sociocultural,
economic, and behavioral determinants of
the patterns of physical activity in modernizing adults Samoans. Why are some adults
able to retain an evidently healthy pattern
of physical activity amidst an obesogenic
environment? While the results of this
cross-sectional study have strong implications, we are limited in the conclusions we
can draw due to the study design. Further
understanding of the socioeconomic structural barriers and individual psychosocial
factors related to physical activity are
required before definitive public health
recommendations can be made.
Prospective studies of physical activity in
the Samoas should also evaluate other traditional activities which provide considerable
forms of physical activity, including fishing,
paddling, and dancing. Such studies should
also take a community-based approach to evaluate participation in physical activities relative
to available facilities and other environmental
conditions influencing lifestyle choices.
Further research is needed to identify incentives and barriers to increasing physical activity
in rapidly modernizing societies (WHO, 2005).
CONCLUSIONS
The results of this study show that regardless of place of residence, sex, age, education
level, household of residence, occupation (in
women), and MLS, participating in farm
work is associated with lower adiposity. In
the face of the rapid changes in lifestyle and
modernization throughout the Samoan archipelago, maintenance of traditional farming
activities may be having a relative protective
health effect through reduced adiposity.
These results reveal important suggestions
for future interventions.
ACKNOWLEDGMENTS
of
We thank the members of the Department
Health, American Samoa, and the
122
E.D. KEIGHLEY ET AL.
Ministry of Health, Government of Samoa,
for their advice and guidance in data collection, as well as local political officials for
their cooperation and help. Thanks to the
research assistants from American Samoa
and Samoa for their hard work and dedication to the project. Also, to the 2002–2003
field teams and field directors staffed by students and alumni from Brown University
and other schools. Above all, we are grateful
to the families, individual participants, and
people of Samoa and American Samoa.
LITERATURE CITED
Baker PT, Hanna J, Baker TS. 1986. The changing
Samoans: behavior and health in transition. New
York: Oxford University Press. p 275–296.
Barnard RJ, Jung T, Inkeles SB. 1994. Diet and exercise
in the treatment of NIDDM: the need for early emphasis. Diabetes Care 17(12):1469–1472.
Dey DK, Bosaeus I. 2003. Comparison of bioelectrical
impedance prediction equations for fat-free mass in a
population-based sample of 75y olds: The NORA
Study. Nutrition 19:858–864.
Galanis DJ, McGarvey ST, Quested C, Sio B, AfeleFa’amuli SA. 1999. Dietary Intake of modernizing
Samoans: implications for risk of cardiovascular disease. J Am Diabetic Assoc 99:184–190.
Greksa LP, Baker PT. 1982. Aerobic capacity of modernizing Samoan men. Hum Biol 54:777–788.
Greksa LP, Pelletier DL, Gage TB. 1986. Work in contemporary and traditional Samoa. In: Baker PT,
Hanna J, Baker TS, editors. The changing Samoans:
behavior and health in transition. New York: Oxford
University Press. p 351–393.
Keighley ED, McGarvey ST, Quested C, MuCuddin C, Viali
S, Maiava T. 2006. Nutrition and health in modernizing
Samoans: evolutionary and adaptive perspectives. In:
Ohtsuka R, Ulijaszek SJ, editors. Nutrition and health
changes in the Asia-Pacific region. Cambridge, England:
Cambridge University Press (in press).
Mead M. 1969. Social organization of Manu’a. Honolulu,
Hawaii: Bishop Museum Press.
McGarvey ST. 1991. Obesity in Samoans and a perspective on the etiology in Polynesians. Am J Clin Nutr
53:1586S–1594S.
McGarvey ST. 1994. The thrifty gene concept and adiposity studies in biological anthropology. J Polynes Soc
103:29–42.
McGarvey ST. 2001. Cardiovascular disease (CVD) risk
factors in Samoa and American Samoa, 1990–1995.
Pac Health Dialog 8(1):157–162.
McGarvey ST, Bindon JR, Crews DE, Schendel DE.
1989. Modernization and adiposity: causes and consequences. In: Little MA, Haas JD, editors. Human
population biology: a trans-disciplinary science. New
York: Academic Press. p 263–279.
O’Meara JT. 1990. Samoan planters: tradition and economic development in Polynesia. Fort Worth, TX:
Holt, Rinehart and Winston, Inc.
Pelletier DL. 1987. The relationship of energy intake
and expenditure to body fatness in Western Samoan
men. Ecol Food Nutr 19:185–199.
Phillips SM, Bandini LG, Compton DV, Naumova EN,
Must A. 2003. A longitudinal comparison of body composition by total body water and bioelectrical impedance in adolescent girls. J Nutr 133(5):1419–1425.
Rush EC, Puniani K, Valencia ME, Davies PS, Plank LD.
2003. Estimation of body fatness from body mass
index and bioelectrical impedance: comparison of
New Zealand European, Maori and Pacific Island
Children. Euro J Clin Nutr 57:1394–1401.
Samoa Department of Statistics. 2003. Census of
Population and Housing 2001. Apia, Samoa:
Government Printing House.
SPC (Secretariat of the Pacific Community). 2002.
Obesity in the Pacific too big to ignore. Secretariat of
the South Pacific, Noumea, New Caledonia.
Swinburn BA, Ley SJ, Carmichael HE, Plank LD. 1999.
Body size and composition in Polynesians. Intl J Obes
23:1178–1183.
U.S. Department of Commerce. 1992. Census of
Population and Housing, American Samoa, 1990.
Washington, D.C.: Government Printing Office.
U.S. Department of Commerce. 2004. Census of
Population and Housing, American Samoa, 2000.
Washington, D.C.: Government Printing Office.
Ulijaszek SJ. 1995. Human energetics in biological
anthropology.
Cambridge,
U.K.:
Cambridge
University Press.
Weitz CA, Greksa LP, Thomas RB, Beall CM. 1989. An
anthropological perspective on the study of work capacity. In: Little MA, Haas JD, editors. Human population biology: a trans-disciplinary science. New York:
Academic Press. p 113–131.
Wessen AF (editor). 1992. Migration and health in a
small society: the case of Tokelau. Oxford, England:
Clarendon Press.
Western Samoa Department of Statistics. 1995. Western
Samoa Census 1991. Apia, Samoa: Government
Printing House.
WHO. 2000. World Health Organization Regional Office
for the Western Pacific. Workshop on obesity prevention and control strategies in the Pacific. Apia, Samoa.
WHO. 2003. World Health Organization Regional Office
for the Western Pacific. Diet, food supply and obesity
in the Pacific, WHO, Manila.
WHO. 2005. Physical activity fact sheet. Online: http://
www.who.int/dietphysicalactivity/publications/facts/
pa/en/. WHO, Geneva.
Документ
Категория
Без категории
Просмотров
2
Размер файла
98 Кб
Теги
adults, adiposity, farming, samoans
1/--страниц
Пожаловаться на содержимое документа