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Cortical bone loss and measurements of the second metacarpal bone. I. Comparisons between adult Guamanian Chamorros and American caucasians

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 59:461-466(1982)
Cortical Bone Loss and Measurements of the Second Metacarpal
Bone. 1. Comparisons Between Adult Guamanian Chamorros and
American Caucasians
C. C . PLATO, R. M. GARRUTO, R. T. YANAGIHARA, K.-M. CHEN, J. L.
WOOD, D. C. GAJDUSEK, AND A. H. NORRIS
Gerontology Research Center, Natimal Institute on Aging, National
Institutes of Health, Baltimore, Maryland (C.C.P., J.L. W., A.H. N.), and
Laboratory of Central Nervous System Studies, National Institute of
Neurolouical and Communicative Disorders and Stroke. National Institutes
of Heal&, Bethesda, Maryland, and the NINCDS Research Center,
Tamuning, Cuam (R.M.G., R.T.Y., K-M.C., D.C.G.)
KEY WORDS Bone loss, Osteoporosis, Bone measurements, Guamanians, Caucasians
ABSTRACT
The amount of radiographically detectable cortical bone, as determined by measurements of the second metacarpal, was evaluated in 42 male
and 45 female Guamanian Chamorros and compared with the degree of bony
demineralization in U.S. Caucasians participating in the Baltimore Longitudinal
Study on Aging of the Gerontology Research Center. All Chamorros were
individually matched to the Caucasian participants for age, sex, and menopause
status. Chamorros of both sexes showed bilateral asymmetry in bone measurements and in the amount of cortical bone. Both Chamorro and Caucasian males
had longer second metacarpals and more cortical bone than females. Caucasian
males, however, had longer and larger second metacarpals than Chamorro males.
Despite differences in the length and total width, Chamorro and Caucasian
participants generally showed no significant differences in the amount of cortical
bone or percent cortical area in the second metacarpal, suggesting that larger
bones may not always indicate greater cortical mass. Although cross-sectional
data suggested apparent age differences in the onset and rate of bone loss
between Chamorros and Caucasians, the numbers of participants were too small
to allow meaningful age-by-age statistical comparisons.
The causes of and pathogenetic relationship
between amyotrophic lateral sclerosis and
parkinsonism-dementia - two relentlessly
progressive, invariably fatal neurological diseases occurring in high incidence among the
Chamorro people of Guam - remain obscure.
Because of the unusually low levels of alkaline
earth metals, particularly calcium and magnesium, in samples of soil and drinking water
from southern Guam and two other geographical isolates of motor neuron disease and parkinsonian syndromes (Gajdusek and Salazar,
1982; Iwata et al., 1978; Shiraki and Yase,
1975), recent studies have focused on the evaluation of mineral metabolism in patients with
these disorders (Yanagihara et al., 1981). As
part of these studies, bilateral hand x-rays
have been obtained from Chamorro patients
and nonaffected controls for comparative
0002-948318215904-0461$02.00 0 1982 ALAN R. LISS, INC.
measurements of bone and for determination
of cortical bone mass. These data are currently being analyzed and will be reported
separately. The purpose of the present report
is to describe measurements of the second
metacarpal bone in neurologically normal Guamanian Chamorros and to compare them with
those obtained from an age-, sex-, and menopause status-matched group of Caucasians
participating in the Baltimore Longitudinal
Study on Aging of the Gerontology Research
Center (GRC).
MATERIALS AND METHODS
Bilateral hand radiographs were obtained
from 42 adult male and 45 adult female GuaReceived March 1, 1982; accepted August 2, 1982
462
C.C. PLAT0 ET AL.
manian Chamorros ranging in age from 21 to
70 years. All participants were neurologically
normal, and were either hospital employees or
individuals who had accompanied their relatives or friends to the Guam Memorial Hospital. Informed consent was obtained from all
participants. The x-rays from each participant
were individually matched with the x-rays obtained from GRC Caucasians of the same sex
and similar age. In certain cases, especially at
younger ages, it was not possible to pair Guamanians with Caucasians of exactly the same
age, but in no instance was the intrapair age
difference greater than 5 years. Female Chamorros and Caucasians were also matched for
menopausal status. Since all but one of the
Chamorro women experienced natural menopause, Caucasian women with hysterectomies
or other forms of induced menopause were
excluded from the study. Although women
were matched for menopausal status at the
time of x-ray, it was not possible to match
them for age at onset of menopause. The average age at onset of menopause was 46.6
years in Chamorros, and 51.6 years in Caucasians.
The GRC participants were of good general
health and of above-average education and socioeconomic status. Detailed descriptions of
this group have been previously reported
(Stone and Norris, 1966; Rowe et al., 1976).
Hand radiographs were taken posteroanteriorly on Kodak RP/S X-Omat film at an average exposure of 1.0 second at 100 mA and 60
kVp without intensifying screens and were
developed at the Baltimore City Hospitals.
Measurements of total width (TW), medullary
width (MW), and length (LEN) at the midshaft
of the second metacarpal bone were performed “blindly” by the same individual (Plato
et al., 1980). Combined cortical thickness
(CCT) was derived by subtracting MW from
TW (i.e., CCT = TW-MW). Percent cortical
area (PCA), the ratio of cortical area to total
area, was calculated using the formula, PCA
= (TW12 - (MW12/(TW12.To a great extent
PCA is independent of body size. Further
descriptions of these measurements and
methods for determining the bone’s midshaft are given elsewhere (Garn et al., 1964;
Garn, 1970; Plato and Norris, 1980).
Because of the small sample size, and since
Guam and GRC participants were individually matched for age, sex, and menopause
status, the data were not separated into age
groups. Bilateral differences among Guamanians, as well a s differences between
Guam and GRC samples, were compared using the Student’s t-test. Regression lines
were derived using a second-degree polynomial model, Y = bo + blX + bzX2 (Ostle,
1954).
RESULTS AND DISCUSSION
Guam-GRC comparisons
Table 1 compares measurements of the second metacarpal bone in the left and right
hands, respectively, of Guamanian and Caucasian males. Caucasian males had significantly
wider and longer second metacarpal bones
than their Chamorro counterparts. Differences in MW, CCT, and PCA were not significant. Caucasian females also had longer and
wider bones than Chamorro females (Table 2).
Although Caucasian women had greater values for all one-parameter variables (TW, MW,
CCT, and LEN) than Guamanian women, they
had smaller (although nonsignificant) values
for PCA, which depends on two parameters
(cortical area and total area). In general, Guamanian women had smaller and more compact
bone than Caucasian women.
Paired bilateral comparisons
Paired bilateral differences 0or mean differences between measurements of the right
and left hands of the same individual are
shown in Table 3. A positive d indicates a
higher mean value in the right hand. Among
Guamanians, significant bilateral differences
were found for TW in both sexes, MW in
males, and CCT in females. Bilateral differences in LEN and PCA were not significant
in either sex. In the GRC group (not shown in
the tables), most d values were also positive.
However, significant bilateral differences were
seen only for TW in males (P< 0.01) and LEN
in females (P < 0.05).
Regression analysis
Postulating a second-order binomial function, we fitted a regression curve of each variable on age. Each distribution was then tested
for best fit by both linear and curvilinear
(quadratic) regression. Predicted values for
MW, CCT, and PCA of both Caucasian and
Guamanian males and females best fit the
models of curvilinear regression on age. Predicted values for CCT are shown in Figure 1.
Only curves for the left hands are presented,
but curves for the right hands were similar.
The regression slopes of the respective variables for Guamanian and GRC males and females showed no significant differences,
mainly because of the wide intragroup variability and the small numbers. Despite the lack
of statistical differences between the regres-
463
BONE LOSS IN GUAMANIANS AND CAUCASIANS
TABLE 1. Comparisons between second metacarpal bone measurements of42 age-matched Guam and GRC male
Dairs
Second metacarpal
bone measurements
Left hands
Total width (mm)
Medullary width (mm)
Combined cortical
thickness (mm)
Length (mm)
Percent cortical area (%)
Right hands
Total width (mm)
Medullary width (mm)
Combined cortical
thickness (mm)
Length (mm)
Percent cortical area (%)
t 0.01.
't Values for
Paired Comparisons
Guam-GRC differences
Group comparisons
Guam
GRC
t
S.E.
Mean
S.E.
Mgan
(d)
S.E.
Mean
(S4
values'
8.80
3.29
5.51
0.10
0.17
0.14
9.39
3.70
5.69
0.11
0.15
0.12
-0.59
-0.42
-0.17
0.16
0.23
0.18
-3.37**
- 1.84
-0.95
65.83
85.00
0.60
1.31
70.93
83.88
0.63
1.03
-4.97
1.09
0.81
1.65
-6.12**
0.66
9.11
3.54
5.57
0.10
0.16
0.14
9.71
4.02
5.69
0.12
0.16
0.14
-0.60
-0.48
-0.12
0.14
0.24
0.20
- 1.99
66.03
84.02
0.45
1.25
71.31
82.12
0.62
1.45
-5.28
- 1.90
0.74
2.06
-7.13**
-0.92
-4.40**
-0.58
a and s;l were calculated before rounding off.
TABLE 2. Comparisons between second metacarpal bone measurements of 45 age- and menopausal status-matched
Guam and GRC female pairs
Paired comparisons
Guam-GRC differences
Group comparisons
Second metacarpal
bone measurements
Left hands
Total width (mm)
Medullary width (mm)
Combined cortical
thickness (mm)
Length (mm)
Percent cortical area (%)
Right hands
Total width (mm)
Medullary width (mm)
Combined cortical
thickness (mm)
Length (mm)
Percent cortical area (%)
Guam
Mean
GRC
S.E.
t
values'
Mean
S.E.
Mean
S.E.
(d)
7.80
2.96
4.84
0.07
0.14
0.10
8.02
2.90
5.12
0.08
0.14
0.11
-0.22
0.06
-0.28
0.10
0.16
0.13
-2.24*
0.39
-2.22*
61.39
84.76
0.44
1.18
65.01
86.11
0.54
1.12
- 1.35
-3.61
0.79
1.32
-4.58**
- 1.02
8.08
3.04
5.04
0.09
0.15
0.12
8.17
2.98
5.20
0.07
0.15
0.12
-0.09
-0.07
-0.15
0.11
0.19
0.16
-0.79
-0.35
-0.97
61.56
84.88
0.41
1.29
65.21
85.75
0.57
1.26
-3.65
-0.87
0.78
1.54
-4.66**
-0.56
(%I)
*P < 0.05.
**P < 0.01.
't Values for and sa were calculated before rounding off.
a
sion slopes of Guamanians and Caucasians,
certain trends are worthy of comment.
1.) After attainment of maturity, neither
TW nor LEN changed Significantly, regardless of hand, sex or population group. At all
ages, TW and LEN were greater in Caucasians than Guamanians and greater in the right
than the left hands.
2.) Males and females of both population
groups, over the age of 40 years showed increasing MW with age. Males younger than 40
years had significantly larger MW than females, but this difference gradually dimin-
ished with advancing age owing to accelerated
bone resorption from the endosteal surface in
postmenopausal women. Guamanian males and
females under the age of 35 years had larger
MW than their respective Caucasian counterparts. This relationship reversed after the age
of 50 to 60 years.
3.) The distribution of predicted values for
CCT (Fig. 1) gives the degree of bone loss
with age, which reflects changes in MW since
TW does not change with age. With the exception of the Guamanian males younger than 40
years, males of both ethnic groups had more
464
C . C . PLAT0 ET AL.
TABLE 3. Paired bilateral dqferences in measurements
ofthe second metacarpal bone in Guamanian
Chamorros
Second metacarpal
bone measurements
Male (N = 42)
Total width (mm)
Medullary width (mm)
Combined cortical
thickness (mm)
Length (mm)
Percent cortical area (%)
Female (N = 45)
Total width (mm)
Medullary width (mm)
Combined cortical
thickness (mm’,
Length (mm)
Percent cortical area (%)
Paired bilateral
comparisons
(right-left differences)
Mgan
S.E.
t
(d)
(sx)
values’
4.45**
0.06**
0.84
0.31
0.25
0.06
0.07
0.08
0.07
0.20
-0.95
0.34
0.56
0.29
0.08
0.21
0.05
0.09
0.09
5.51**
0.88
2.26*
0.17
0.12
0.17
0.80
0.98
0.15
0.58
- 1.69
> P 2 0.01.
**P < 0.01. ‘t Values ford and s;, were calculated before rounding off.
*0.05
-E
-E
7.0
‘z
6.0
E
8
5.0
bone and lost less bane with age than did
females. The reason for the smaller amount of
cortical bone in younger Guamanian males is
not clear from the present data. I t may reflect
secular changes in the Guamanian society or
enviranment. The possibility of secular effects
needa to be given further consideration since
Gumanian males in the age groups having
low values for CCT were born after the end of
World War 11, which marked the beginning of
rofound sociocultural changes on Guam.
early every aspect of daily life of both sexes,
including nutritional, occupational, residential, and recreational preferences or habits,
was affected by these changes, but the major
impact was upon men.
At younger ages, Caucasian females had
greater predicted CCT than Chamorro females, but after age 60 the situation was reversed and Caucasian women had less cortical
bone than their Guamanian counterparts. Both
female groups began to lose cortical bone after
the age of 40, but with increasing age Cauca-
R
v)
3
....J
..-.
3
-1
-0.-C.
-0
e
s
m
8
e
L
e
4.0
3.0
,
I
20
30
50
40
60
70
AGE (years)
Fig. 1. Predicted combined cortical thickness of the
left second metacarpal bone of male and female Chamorros (Guam) and Caucasians (GRC). The curvilinear
regression equations are Guam males: Y = 2.393 +
0.148X - 0.0016X2,r2 = 0.18, P < 0.02; Guam females:
Y = 5.443 + 0.0032X - 0.0003X2, r2 = 0.33, P < 0.001.
GRC males: Y = 7.463 - 0.0527X + 0.0003X2, r2 =
0.17, P < 0.03; GRC females: Y = 3.884 + 0.0954X 0.0014X2,
r2 = 0.44, P < 0.001.
BONE LOSS IN GUAMABiIANS AND CAUCASIANS
sian females lost bone more rapidly than Chamorro females. It is unclear from the present
data whether this differential loss of cortical
bone between Chamorro and Caucasian
women is due primarily to genetic or cultural
factors, or to a combination of both. The
regression lines for predicted PCA (which is
relatively independent of bone size) followed
very closely those for CCT. That is, Caucasians of both sexes had greater PCA than
Chamorros during youth, but the situation was
reversed after age 60.
In earlier studies on measurements of the
second metacarpal bone of Caucasian males
and females, we demonstrated that progressive bone loss occurred with increasing age,
that the TW and LEN of the second metacarpal did not change sigmfkantly after adulthood, that the second metacarpal of the right
hand was larger (with greater cortical mass)
than the left regardless of hand dominance,
that males had longer and wider second metacarpal bones than females, and that postmenopausal women lost more bone than men of
the same age (Plato et al., 1980; Plato and
Nonis, 1980; Plato and Purifoy, 1982). This
study c onf i i e d our earlier observations and
also revealed discrete differences between
bone measurements in Chamorros and Caucasians. We cannot ascertain from our sample
whether these differences are due to biological
variation, to sampling error, to nutritional
habits, or to socioeconomic conditions. Further studies are currently under way in both
populations to clarify the biological significance of these differences.
ACKNOWLEDGMENTS
The field assistance of Mr. Manuel T. Cruz,
Mr. Francisco C. Leon Guerrero, Mr. Luis T.
Munoz, Mr. Jose M. Torres, Mrs. Mary E.
Hernandez, and Dr. Olivia T. Cruz of the
NINCDS Research Center of Guam is gratefully acknowledged. We also thank Mr. James
Pauley and the x-ray technicians of the Guam
Memorial Hospital for their cooperation, Mrs.
465
Janice DiGracia and Mrs. Kathleen Fox of the
Gerontology Research Center for their invaluable assistance throughout the course of this
project, Dr. Larry Brant for his statistical consultation, and Miss Catherine Daum for her
patient help in the preparation of the manuscript.
LITERATURE CITED
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sclerosis and parkinsonism-dementia in high incidence
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Garn, SM (1970)The Earlier Gain and Later Loss of
Cortical Bone. Springfield, Illinois: Thomas.
Garn, SM, Rohman, CG, and Nolan, P (1964) The developmental nature of bone changes during aging. In JE
Birren (ed): Relations of Development and Aging.
Springfield, Illinois: Thomas, pp. 41-61.
Iwata, S, Sasajima, K, Yase, Y, and Chen, K-M (1978)
Report of Investigation of the Environmental Factors
Related to Occurrence of Amyotrophic Lateral Sclerosis
in Guam Island. Tokyo: Ministry of Education.
Ostle, B (1954) Statistics in Research. Basic Concepts and
Techniques for Research Workers. Ames: Iowa State
University Press, pp. 223-224.
Plato, CC, and Nonis, AH (1980) Bone measurements of
the second metacarpal and grip strength. Hum. Biol.
52:131-149.
Plato, CC, and Purifoy, F E (1982) Age, sex and bilateral
variability in cortical bone loss and measurements of the
second metacarpal. Growth 4.6:100-112.
Plato, CC, Wood, JL, and Norris, AH (1980) Bilateral
asymmetry in bone measurements of the hand and lateral hand dominance. Am. J. Phys. Anthropol. 5227-31.
Rowe, JW,
Andres, R, Tobin, JD, Nonis, AH, and Shock,
NW (1976) The effect of age on creatinine clearance in
men: A cross sectional and longitudinal study. J. Gerontol. 311:155-163,
Shiraki, H, and Yase, Y (1975) Amyotrophic lateral sclerosis in Japan. In P Vinken and GW Bruyn (eds): Handbook of Clinical Neurology, Vol. 22. New York NorthHolland, pp. 353-419.
Stone, JL, and Nonis, AH (1966) Activities and attitudes
of participants in the Baltimore Longitudinal Study. J.
Gerontol. 21:575-580.
Yanagihara, RT, Garruto, RM, Gajdusek, DC, Tomita, A,
Sobue, I, Chen, K-M, and Gibbs, CJ Jr (1981) Calcium
metabolism in Guamanian Chamorros with amyotrophic
lateral sclerosis and parkinsonism-dementia. Abstracts
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September 20-25. International Congress Series 548.
Amsterdam: Excerpta Medica, pp. 375-376.
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