Meeting Summary
Agenda and Abstracts
Speaker Roster

Strong Heart Study

Barbara Howard, Ph.D.
MedStar Research Institute

The Strong Heart Study includes longitudinal cohort and family/genetic studies of cardiovascular disease (CVD) among American Indian men and women. This report focuses on longitudinal data from the cohort study, whose population consists of 13 Tribes in three geographic areas (Arizona, Oklahoma and North and South Dakota). Employing standardized methods, the cohort study is designed to estimate CVD mortality and morbidity and the prevalence of known and suspected CVD risk factors and target organ damage among American Indians and to assess the significance of these risk factors over time. It is the largest cohort of individuals with diabetes under continuous CVD surveillance in the U.S. During the 19891991 baseline examination, 4,549 tribal members (62% of the total population aged 45-74 years) were examined. A second examination, including 89% of surviving original cohort members, was conducted between 1993 and 1995. A third and final exam in 1998-1999 included 88% of the surviving cohort (3,197 participants).

Obesity is an important health problem in American Indians, with respect to both diabetes and CVD. Using NHLBI guidelines, Mmore than 75% of SHS were overweight at baseline, and 44% and 55% of men and women, respectively, were obese. Obesity is more prevalent in younger SHS participants, and in those with diabetes. With the exception of insulin concentration, metabolic measures such as lipoproteins and blood pressure do not change substantially with increasing BMI in cross-sectional analyses.

To examine determinants of weight change over time in SHS, non-diabetic individuals who did not develop either cancer or diabetes during follow-up period were identified. Mean BMI, BMI categories, and weight change over an average of 7.9 years of follow-up are summarized in the following table:

Men (N = 437)
Women (N = 624)
Baseline BMI
28.0
30.0
% Normal (18.5 to <25)
18.5
17.8
% over weight (25 to <30)
45.8
34.6
% obese (>=30)
35.7
46.8
Mean wt change (kg)
0.76 range (-27 to 28)
1.62 range (-32 to 29)

44.76% of the men and 62.9% of the women reported spending zero hours per week performing physical activity and few performed more than 5 hours per week. In mLinear models predicting weight change between the baseline and 3rd examinations were fitted separately for men and women. In men, age was negatively related and education positively to weight change (r squared =.0583). In women, age and baseline BMI were negatively related and education was positively related to weight change (r squared =.1265). Weight change was unrelated to measures of baseline income or physical activity in these adjusted models.

In this population with high rates of diabetes and CVD, it is clear that by the later adult years there are no easily remediable determinants of wt gain. Current emphasis in Indian communities is being placed on nutrition and activity programs in schools and young adults. However, the low levels of physical activity suggest that community programs designed to increase activity levels in middle aged and older adults are needed.

References

  1. Gray, R.S., Fabsitz, R.R., Cowan, L.D., Lee, E.T., Welty, T.K., Jablonski, K.A., and Howard, B.V. Relation of generalized and central obesity to cardiovascular risk factors and prevalent coronary heart disease in a sample of American Indians: the Strong Heart Study. Int. J. Obesity 24:849-860, 2000.
  2. Howard, B.V., Welty, T.K., Fabsitz, R.R., Cowan, L.D., Oopik, A.J., Lee, E.T., Yeh, J., Savage, P.J., and Lee, E.T. Risk Factors for Coronary Heart Disease in Diabetic and Non-Diabetic American Indians: The Strong Heart Study. Diabetes, 41;(Suppl. 2):4-11, 1992.
  3. Lee, E.T., Welty, T.K., Fabsitz, R., Cowan, L.D., Le, N.-A., Oopik, A.J., Cucchiara, A.J., Savage, P.J. and Howard, B.V. The Strong Heart Study - A Study of Cardiovascular Disease in American Indians: Design and Methods. Am J Epidemiology 132:1141-1155, 1990.
  4. Welty, T.K., Lee, E.T., Yeh, J. Cowan, L.D., Go, O., Fabsitz, R.R., Le, N.A., Oopik, A.J., Robbins, D.C., Howard, B.V. Cardiovascular Disease Risk Factors Among American Indians: The Strong Heart Study. American Journal of Epidemiology, 142(3):269-287, 1995.

 

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