Data from the largest epidemiological study of cardiovascular disease (CVD) and its risk factors in the American Indian community may indicate racial differences in the development of hypertension and that different risk factors are more predictive in men than in women.

Peng Li, MD, MPH, of the Oklahoma State Department of Health (OSDH), representing the researchers from the Strong Heart Study, discussed the findings today in New York City at the 21st Annual Scientific Meeting of the American Society of Hypertension (ASH 2006). Dr. Li participated in the Strong Heart Study at the University of Oklahoma Health Sciences Center before he joined the OSDH.

Dr. Li explained, “There is limited information available concerning CVD and risk factors such as hypertension in this at-risk population. Our findings indicate racial and gender disparities in incidence rates of developing hypertension, necessitating further population-specific research into which risk factors are most predictive.”

Using JNC-VII criteria, the annual incidence rate of hypertension was 6.4% (6.7% in men and 6.2% in women). The incidence rates among American Indian populations in this study were higher than similar studies (TOHP-1), but lower than others (HDFP, etc).

Baseline prehypertension, albuminuria, diabetes, obesity (BMI >=30), waist-hip ratio and percent of body fat were significantly related to the onset of hypertension. Stepwise logistic regression models indicated that baseline blood pressure, particularly SBP, was also a significant predictor of hypertension. The relationships between smoking and alcohol drinking with hypertension in this population were not clear.

Dr Li noted that, “We found that within this population, there were significant gender differences in which risk factors were more significant predictors of hypertension. Waist-hip ratio was more important for men while weight gain was more important for women.”

In the study, a total of 4,549 American Indians (1,846 men and 2,703 women) participated in a baseline examination between July 1989 and January 1992 to determine the presence of specific risk factors. Out of this group, 3,638 (1,384 men and 2,254 women) survivors underwent a second examination between July 1993 and December 1995. Among them, 2,249 (838 males and 1,411 females) participants who were free of hypertension at baseline, and who participated in the second examination were included in the estimation of hypertension incidence rate. The average follow-up time between the baseline and second examination was 3.9 years.

The Strong Heart Study, supported by the National Heart, Lung, and Blood Institute and begun on October 1, 1988, is the largest epidemiological study of American Indians ever undertaken to examine cardiovascular disease and its risk factors among American Indian men and women. The study included 13 American Indian tribes and communities in three geographic areas: an area near Phoenix, Arizona, the southwestern area of Oklahoma, and western and central North and South Dakota.

Cardiovascular disease has been the leading cause of death in American Indians and the general United States population since the 1980’s. Indian Health Service (IHS) data indicate that CVD mortality rates in American Indians vary among tribes, and some tribes have higher and some have lower rates than that of the general US population.

American Society of Hypertension (ASH)