The purpose of the proposed study is to determine and compare the long term (thirty year) relationship of total cholesterol and mortality in blacks and whites in a predominantly urban (Charleston, SC) and a predominantly rural (Evans County, GA) cohort with special emphasis on the investigation of the association of low cholesterol to all cause, cardiovascular disease (CVD), and non-CVD mortality. Because of the paucity of data on blacks and women, the data from the combined Charleston and Evans County studies will provide important information on the existence of a low cholesterol/mortality association and potential effect modifiers in these understudied populations.
The specific aims are to: (1) determine if a J-shaped or U-shaped relationship between cholesterol and all-cause and non-CVD mortality is observed in the Charleston (CHS) and Evans County Georgia (ECGHS) cohorts of blacks and whites; (2) investigate the existence of racial, gender, and place of residence (urban versus rural) differences in the relationship of cholesterol to mortality with particular emphasis on identification of racial and gender differences in the low cholesterol/mortality association; (3) determine if socioeconomic status (SES) modifies the effect of cholesterol on mortality in black and white women and black and white men and to determine if the effect modification of SES, if found to exist, is different in urban and rural settings. The CHS and ECGHS were both begun in 1960 as prospective cohort studies designed to study risk factors of cardiovascular disease in biracial communities. The CHS cohort comprised a random sample of black and white men and women residents of Charleston County SC who were 35 years of age or older in 1960 (n=2281). For the ECGHS (n=3102), 100% of the population of Evans County GA who were 40 years and older and 50% of the residents 15-39 years of age were recruited (92% response rate). Data will be analyzed both separately for each cohort for comparison across cohorts and will be pooled for combined analyses. Cox proportional hazards regression analyses will be used to model the relationship of total cholesterol to the following mortality endpoints: all cause, CVD, CHD, stroke, cancer, nonCVD/noncancer. Racial and gender differences in the relationship of cholesterol to mortality will be investigated through both race-sex stratified analyses and inclusion of interaction terms for these variables in the regression model. Urban/rural differences in the cholesterol/mortality association will be evaluated by testing for significance of difference in the regression coefficients for the cholesterol term in the regression models run separately for the CHS and ECGHS cohorts. The effect modification of the cholesterol/ mortality association by SES will be investigated by comparison of the regression coefficients for cholesterol in models analyzed separately by high and low SES strata and in models containing an SES by cholesterol interaction term.
