Dec 17, 1980 - International Health, 1699 HSW, University of California, San. Francisco, CA ... ulations in Samoa than the Samoan population in Hawaii. Materials and ... members of the Pennsylvania State University Migration. Project.
Massive Obesity in a Migrant Samoan Population IVAN G. PAWSON, PHD,
AND
CRAIG JANES, MA
Abstract: Peoples of the Pacific Islands tend to become overweight when they migrate or are exposed to modernization in situ. Recent evidence suggests that Samoans are particularly susceptible, exhibiting a high prevalence of obesity and hypertension following migration to Hawaii. We report the preliminary results of a survey of height, weight, blood pressure, and fasting plasma glucose (FPG) among an urbanized Samoan community in the San Francisco Bay Area. Although
the participants' average height fell between the 25th and 50th percentile of the US population, about onehalf our sample exceeded the 95th percentile for weight. The extreme overweight was accompanied by elevated blood pressure and, in females, by elevated FPG. The massive adult weight of migrants from the Pacific Islands carries serious public health implications for areas that support large migrant communities. (Am J Public Health 1981; 71:508-513.)
Introduction
blood pressure are linked to the degree of exposure to western influences and lifestyles, then the Samoan population in California should exhibit greater contrasts to the native populations in Samoa than the Samoan population in Hawaii.
One of the expected consequences of migration to a modem industrialized country from a rural, nonwestern environment and of the accompanying alterations in traditional dietary and exercise habits is increased body weight. Peoples of the Pacific Islands seem particularly prone to becoming overweight and to developing concomitant degenerative and metabolic disorders when they migrate or are exposed to increased modernization. The trend has prompted several investigations into the public health implications of resettlement programs'-4 and the consequences of exploitation of island resources.5 -7 Continued migration has led to the growth of sizable Pacific Islander communities in the mainland United States, but because these peoples are frequently classified in official records under the ethnic category '"Other," no formal estimates of population size are available. In California, a major recipient state for migrants from the Pacific Islands, the size of the Samoan community alone is estimated to be between 60,000 and 80,000 persons,* most of whom live in the metropolitan areas of San Diego, Los Angeles, and San Francisco. Because previous studies have shown that Samoans livingin semi-urban conditions in Hawaii exhibit a substantially higher prevalence of obesity and hypertension than their counterparts in Samoa,'0, we decided to undertake a pilot survey in San Francisco to determine the frequency of these conditions among Samoans who have moved to the mainland. We hypothesized that if increased weight and elevated
From the Department of Epidemiology and International Health, University of California, San Francisco. Address reprint requests to Ivan G. Pawson, PhD, c/o Editor, Epidemiology and International Health, 1699 HSW, University of California, San Francisco, CA 94143. This paper, submitted to the Journal July 30, 1980, was revised and accepted for publication December 17, 1980. *Information supplied by Department of Health and Human Services, Region IX, Office of Planning and Evaluation.
508
Materials and Methods Study Population The Samoans of our study reside in the southern part of San Francisco and adjacent areas of San Mateo County. The structure of their community centers around 27 churches in the Bay Area. The traditional Samoan hierarchy of chiefs functions in a semi-formal capacity, although the extent to which it can exert social control over the community is open to question. The Office of Samoan Affairs, Inc., a national council of chiefs and community leaders, promotes adult education and other programs that ensure the maintenance of cultural identity and assists immigrants in integrating themselves as well as is possible into the host culture.
Sampling Procedures Because of the-virtual absence of ethnogra-phic, medical, or other literature on Pacific Island peoples who have migrated to the United States, there are no reliable estimates of population characteristics such as size, distribution, medical history, health status, or mortality. In pilot surveys such as ours, lack of background data makes the selection of a representative sample difficult. We chose church congregations as our sampling base because the great majority of Samoan families regularly attend church, rendering estimates of various biological parameters obtained from this source more likely to reflect true population characteristics. With the help of church ministers, who exert considerable influence in the Samoan community, we were able to examine most members of two church congregations and about 50 per cent of a third one. We also examined members of a Samoan adult education class on the recommendation of a minister, AJPH May 1981, Vol. 71, No. 5
MASSIVE OBESITY IN MIGRANT SAMOANS
himself a member of the class. In all, 179 individuals were examined (88 males, 91 females-Table 1). Because of the casual attitude with which most Samoans view overweight, we deem it unlikely that an individual's weight had any bearing on his or her decision to participate. Examinations took place after Sunday service or during scheduled church functions. We report here data on height, weight, and triceps skinfold, measured according to standardized techniques." Blood pressure was taken in the resting state, by the same observer (IGP) using a mercury sphygmomanometer fitted with the appropriate cuff size for individuals of large or normal size. Fasting glucose levels were determined using venous blood and Dextrostix reagent strips which were read with the Ames reflectance meter.
MALES
E ._L x1
18 -29
30-39
40-49
50 & over
Age in years
KEY
L
Comparison Data Comparison data were available for Samoan populations (Table 1) in American Samoa and Hawaii9 and in Western Samoa.'0 In each location, data were collected by members of the Pennsylvania State University Migration Project. The data from Western Samoa, described by Baker and Hanna,'0 derive from two villages chosen for their remoteness from the capital, Apia, and comprise 318 adults. The composition of comparison samples in American Samoa and Hawaii are reported by McGarvey and Baker.9 A total of 2,219 adults (1,688 in American Samoa, 591 in Hawaii) were examined from 1975 to 1977. In American Samoa, subjects were recruited from the capital, Pago Pago, and the surrounding areas. In Hawaii, they were recruited from rural areas on the north and western shores of Oahu, as well as from urban areas in Honolulu. In all cases, individuals were recruited voluntarily and examined either in the home or in a ceremonial house. Measurement techniques-for example, the use of blood pressure cuff size appropriate to the subjects' arm circumference-were similar in all studies. However, in view of uncertainties over the background, composition, and representativeness of these samples, and the fact that different investigators collected the data, detailed comparisons between them are unwarranted. We present the data here only to emphasize the unique physical characteristics of the California population, compared to those in Hawaii and Samoa.
1: Western Samoa
i_ 2: American Samoa
FEMALES 3: Hawaii - 4: California
E
.S_-
18 - 29
30 - 39
40 - 49
50 & over
Age in years
FIGURE 1-Height in Four Adult Samoan Subpopulations
Results Height
Figure 1 depicts adult height of Samoans living in San Francisco compared with populations in Western Samoa, American Samoa, and Hawaii. In general, the stature of adult Samoan males is close to the 25th percentile of height (171 cm) in the US population,'2 whereas females fall between the 25th (158 cm) and 50th (162 cm) percentiles. The
TABLE 1-Sample Sizes of Samoan Subpopulations American Samoa
Western Samoa
Male
Age (years)
19-29 30-39 40-49 50+
TOTAL
N
%
37 26 24 41 128
29 20 19 32 100
AJPH May 1981, Vol. 71, No. 5
Female
Male
Female N
%
N
%
N
62
33 22 17 28 100
177 151
26 22 19 33 100
277 211 209 298 995
41
33 54 190
134 231 693
Hawaii
California Female
Male %
N
28 85 52 21 21 45 30 67 100 249
Male
Female
%
N
%
N
%
N
%
34 21 18 27 100
152 61 73 56 342
44 18 21 16
14 21
16 24
20 33 88
23 37 100
26 23 23 19 91
29 25 25 21 100
99
509
PAWSON AND JANES
MALES
oo.c
relatively small size of the California sample makes it difficult to judge whether the differences between the other three groups are biologically significant. Indeed, given our uncertainty about the background of migrant populations in Hawaii and California, and the difficulty in working with published variances and means, it is doubtful whether detailed comparisons are justified at this stage. However, to derive a measure of overall differences between the groups, we calculated pooled means and variances from the published agespecific means and variances for Hawaiian and Samoan samples" and compared them with similar values from our own study. Values of the t statistic for comparison of means in the Califoria population with each of the other three groups were insigificant once probability values were corrected for the number of groups in the comparisons (four), suggesting that sampling bias may have accounted for the higher heights seen in our sample. Increased stature among migrants would be expected if migration takes place early in the life cycle; however, all participants in our study were born in Samoa and spent their early years there before moving to California.
|
~90
70 -
| .s
s
18-29
30 -39
s
40 -49 Age in years
50 & over
KEY
FEMALES 110
L=l 1: Western Samoa 11 2: American Samoa 3: Hawaii
100
4: California
so:@90
: @
Z
so1
;
:g
@@.
i
Weight Figure 2 shows weight among the same four subpopulations. The weight difference between the Western Samoa population and the populations in American Samoa, Hawaii and California is striking. Among individuals in our survey, 55 per cent of males and 46 per cent of females exceed the age specific 95th percentile for weight in the US @@l |population.'2 Pooled mean and variance estimates were calculated for each sex from the published data for populations B in Samoa and Hawaii and compared with the California g sample by means of the t test. Even when corrected for the number of groups being compared, the t statistic indicated that males and females in the California subpopulation were significantly heavier (.05 > p > .01) than samples from Samoa or Hawaii. The average adult weights of individuals |:= in our samples, 103.2 kg among males and 93.05 kg among
@i
70
18-29
@ |
30 -39
40 -49
females, suggest that the California Samoan population may be the world's heaviest.
50& over
Age in years
FIGURE 2-Weight in Four Adult Samoan Subpopulations
TABLE 2-Average Triceps Skinfold Measurements (mm) in Migrant and Native Samoans Age Groups Females
Males 20-29 N
sd
40-49
30-39
x
N
sd
x
N
sd
20-29
50+
x
N
sd
x
N
sd
30-39
x
N
sd
50+
40-49
x
N
sd
x
N
sd
k
27.4 211 37.3 38.0 209 39.4 298 12.8 151 18.6 231 18.5 235 17.9 134 Amercan 134 12.4 14.6 13.6 10.6 10.4 13.9 6.0 10.2 Samoa1 34.7 73 37.2 56 18.6 67 28.7 61 32.8 19.8 114 17.3 52 18.4 45 61 Hawaii1 11.2 7.8 8.5 10.9 11.5 7.9 11.0 9.4 17.7 25 31.8 20 32.7 20 17.2 18 25.2 21 31.3 19.8 31 20.5 20 California 13 9.9 6.7 10.9 8.2 8.7 10.9 7.9 8.3 Data from
510
McGarvey and Baker, 1979 AJPH May 1981, Vol. 71, No. 5
MASSIVE OBESITY IN MIGRANT SAMOANS Key *
p California .A Hawaii -+ American Samoa 0 Western Samoa -
+
-
o Males
15o r 140
A_--
+;+>
1401,___+-
A-
1301-
Females
150 r
.
F
-
W-_
130 1
,
_---
+ --I
120 1
120p-
E E 110 1
110 F
I
Lu
ng
1001-
100
F
0o
F
Lu -J
gol-
A,
a
80
F
80o
701-
70 p
60
60 I
25
I
35
I
45
55
I
65
a
l
25
35
Il
45
55
65
AGE IN YEARS
FIGURE 3-Blood Pressure in Four Adult Samoan Subpopulations
Skinfold Thickness Table 2 shows the measurements of the thickness of the triceps skinfold in migrant Samoan populations in Hawaii and California, and in the native population of American Samoa. In all age groups, and in both sexes, mean skinfold values exceed the 80th percentile for US whites whereas mean values for females in American Samoa over the age of 30 exceed the 95th percentile. The distribution of skinfold thicknesses among the four subpopulations is unexpected in view of the massive adult weights recorded for the migrants, particularly those in California. We calculated pooled mean values for the triceps skinfold, in the manner described above. When these values were compared using the adjusted t statistic, no significant differences were observed between the group means, even though adult weight was significantly greater in the California subpopulation. This suggests that the triceps skinfold may not be reliable as an indicator of adiposity in Samoans. If the extra weight of the California sample is carried as fat, as seems likely, the extra accumulation is not reflected by skinfold thickness at the triceps. However, compression measurement of skinfold thickness on obese subjects is unreliable and may be inappropriate in a population where obesity is so prevalent. Blood Pressure To date, analysis of health outcomes in relation to the massive adult weights encountered among the Samoan miAJPH May 1981, Vol. 71, No. 5
on indicators of cardiovascular and metabolic risk. Figure 3 shows comparison of blood pressure from the California sample with similar data from samples in Samoa and Hawaii. Although these data derive from measurements made by many different investigators, it appears that blood pressure variation parallels variation in weight. However, partial correlation analysis, in which the relationship of body mass index (weight/height2) with blood pressure was examined, while holding constant the effect of age, revealed a strong positive correlation in females, but a weak and statistically insignificant correlation in males. The preliminary findings suggest a different pattern of weight/ blood pressure relationships in our samples than in those studied by Hanna and Baker8 in Hawaii. In the Hawaiian sample, weight was strongly associated with blood pressure in males, whereas in females age was the strongest predictor. Table 3 illustrates the percentage of migrant and native Samoan populations that exhibit definite hypertension. Although the size of individual age groups (especially in our sample) is too small to warrant detailed analysis, it is clear that males as a group exhibit a higher prevalence of hypertension than the US norm, whereas Samoan females exhibit a somewhat lower prevalence. While the distribution of hypertension among Hawaiian and Californian samples was similar (x2 = 3.0 for males, x2 = 0.21 for females; .05 < p), males and females in each sample differed significantly from each other (X2 = 6.12; .05 > p > .01 for Hawaiian Samoans, XI = 6.96; .01 > p > .001 for California Samoans). Strati-
grant population has centered
511
PAWSON AND JANES TABLE 3-Proportion of Hypertensive' Individuals in Samoan Migrant and Native Populations A. Migrant Populations in Hawaii and California Males
Females
35-54
18-34
55+
18-34
All Ages
Age
N
%
N
%
N
%
N
Hawaii2 California U.S.3
14/80 6/24
17.5 25.0 7.0
22/81 16/38
27.2 42.0 22.9
8/36 6/25
22.2 24.0 34.5
44/197 28/87
%
22.3 10/149 32.8 2/40 19.2
B. Native Populations in American Samoa and Western Samoa (All Ages) "Traditional"
% American Samoa4 % Western Samoa4 (Both Sexes)
N
35-54
All Ages
55+
%
N
%
N
%
6.7 5.0 3.0
17/75 8/38
22.7 21.1 18.1
7/29 4/13
24.1 30.8 40.0
"Intermediate"
N
%
34/253 13.4 14/91 15.4 17.1
"Modem"
Male
Female
Male
Female
Male
Female
9.0
18.0
20.0
16.0
24.0
21.0
6.0
Systolic Pressure 2 160 mm Hg or Diastolic Pressure 2 95 mm Hg. 2Data from Hanna & Baker (1979). 3Health and Nutrition Examination Survey (Roberts & Maurer, 1977). 4P. T. Baker, Personal Communication.
fication of the American Samoan sample on the basis of proximity to Pago Pago (and presumed exposure to western diet and lifestyles) illustrates a downward trend in the proportion of hypertensive individuals as one moves away from the capital. Male Samoan nonmigrants designated as "modem" exhibit a degree of hypertension similar to their counterparts in Hawaii, female nonmigrants exhibit a higher prevalence than either the Hawaiian or Californian subpopulation. These findings are in direct contrast to the relatively low rate of hypertension in Western Samoa. Fasting Blood Glucose Blood glucose levels were examined in 68 males and 75 females. Although all individuals had been requested to attend the examination in a fasting state, interviews revealed that only 40 of the male sample (59 per cent) and 43 of the female sample (57 per cent) could be considered truly fasting, the remaining individuals having had sweetened coffee or other sugar containing beverages immediately before the examination. We considered the fasting sample too small for detailed analysis, but it was interesting to note that 18 per cent of the male fasting sample, and 9 per cent of the female fasting sample had glucose levels that exceeded the 95th percentile for fasting blood glucose in a US white population.'3 When the effects of age were controlled, blood glucose correlated significantly with body mass index in females (r = 0.36, .05 > p > .01) but not in males (r = -0.04, .05 < p).
Discusssion The data presented here reflect the initial stages of what we expect to be a more extensive investigation of obesity 512
and related health risks in this population. Detailed discussion of our data is unwarranted at this time because of uncertainties over the background of the Califomia Samoan population, the chronology of weight gain among migrants, and the general lack of demographic information. For example, we are unsure of whether the obese Samoan adults we see so frequently are in some way a 'selected" group of Samoans, becoming fat before they migrate. At present, it is uncertain whether the obesity we have seen represents excess weight gained before migration, after migration, or during both periods. In addition, the cultural beliefs that determine attitudes toward food and obesity are currently unknown, but may be of prime importance in understanding the etiology of obesity in this population. If these problems can be resolved, the California Samoan population should prove a useful model for the study of obesity in humans. Given the present uncertainty over etiology, risks, morbidity, and mortality that surrounds this condition, such a model could aid greatly in understanding its natural history.
ACKNOWLEDGMENTS Supported in part by National Institutes of Health Research Career Development Award K04-AG00022 and by grants from the University of California, San Francisco, School of Medicine.
REFERENCES 1. Prior IAM: Nutrition and epidemiology. J NZ Dietetic Assoc 1966; 20:9-17. 2. Prior IAM: Cardiovascular epidemiology in New Zealand and the Pacific. NZ Med J 1974a; 80:345-352. 3. Prior IAM, Stanhope J, Evand JS, Salmond CE: The Tokelau Island migrant study. Int J Epidemiol 1974b; 3:225-232. 4. Prior IAM, Beaglehole R, Davidson F, Salmond CE: The relationship of diabetes, blood lipids and uric acid levels in Polynesians. Adv Metab Disord 1978; 9:241-261.
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MASSIVE OBESITY IN MIGRANT SAMOANS 5. Zimmet P, Seluka A, Collins J, et al: Diabetes mellitus in an urbanized isolated Polynesian population. Diabetes 1977; 26:1101-1108. 6. Zimmet P, Bjorntorp P: Adipose tissue cellularity in obese nondiabetic men in an urbanized Pacific Island (Polynesian) population. Am J Clin Nutr 1979; 32:1788-1791. 7. Ringrose H, Zimmet P: Nutrient intakes in an urbanized Micronesian population with a high diabetes prevalence. Am J Clin Nutr 1979; 32:1134-1341. 8. Hanna JM, Baker PT: Biocultural correlates to the blood pressure of Samoan migrants in Hawaii. Hum Biol 1979; 51:480-497. 9. McGarvey ST, Baker PT: The effects of modernization and migration on Samoan blood pressures. Hum Biol 1979; 51:461479.
10. Baker PT, Hanna JN: Modernization and biological fitness of Samoans: A progress report on a research program. IN: Proceedings of the 1979 Seminar on Migration and Health, Epidemiology Unit, Community Health Department, Wellington Hospital, Wellington, New Zealand. 11. Weiner JS, Lourie JA: Human Biology: A Guide to Field Methods. Philadelphia: F. A. Davis, 1969. 12. Abraham S, Johnson CL, Najjar MR: Weight and height of adults 18-74 years of age: United States, 1971-74. DHEW Pub. No. (PHS) 79-1659, National Center for Health Statistics, Hyattsville, MD, 1979. 13. Barrett-Connor E: Factors associated with the distribution of fasting glucose in an adult community. Am J Epidemiol 1980; 112:518-523.
Kellogg Pharmaceutical Clinical Scientist Fellowships Available Applications from qualified candidates are now being accepted for the Kellogg Pharmaceutical Clinical Scientist Fellowships offered by the University of Minnesota in conjunction with the St. Louis Park Medical Center Research Foundation, Minneapolis, MN. Ten fellowships remain to be awarded during the Fall 1981 academic term. Each three-year fellowship carries a stipend of $10,000 per year of study leading to the PhD degree in Social and Administrative Pharmacy. Deadline for application for the fellowship is May 1, 1981; final decisions by the admissions committee will be made by May 15, 1981. Early application is encouraged. The Program, funded by the W. K. Kellogg Foundation of Battle Creek, Michigan, represents an endeavor to fulfill a need identified by the 1975 Report of the (Millis) Study Commission on Pharmacy. During the course of study, experienced practicing pharmacists will fulfill university coursework and also participate in projects at various pharmacy practice sites. Degree credit will also be earned through these projects, the nature of the projects to be determined according.to the goals and interests of the individual fellows. Graduates of the Program are expected to become the major community resource for the application of pharmacy knowledge, to contribute significantly to the quality of drug-related services provided in their communities, and to assume leadership roles in drug-related research. Criteria on which candidates will be judged include: a clinically-oriented pharmacy education, a minimum of two years clinical pharmacy practice experience relevant equivalent, professional licensure, superior prior academic performance, demonstrated leadership ability, and letters of recommendation. Specific information concerning the program and the formal application procedure may be obtained by writing to: Kellogg Pharmaceutical Clinical Scientist Program, Attention: Dr. Albert I. Wertheimer, College of Pharmacy, University of Minnesota, Minneapolis, MN 55455.
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