Racial differences in associations of blood pressure components in young adulthood with incident cardiovascular disease by middle age: Coronary Artery Risk Development in Young Adults (CARDIA) study

IMPORTANCE: Data are sparse regarding which blood pressure (BP) components in young adulthood optimally determine cardiovascular disease (CVD) by middle age. OBJECTIVES:      To assess which BP components best determine incident CVD events in young adults and determine whether these associations vary by race and age at BP measurement. DESIGN, SETTING, AND PARTICIPANTS: Using data from the Coronary Artery Risk Development in Young Adults (CARDIA) study, this study assessed the longitudinal race-stratified associations between BP and cardiovascular outcomes. CARDIA is a community-based cohort that recruited black and white individuals (age range, 18-30 years) from March 26, 1985, through June 7, 1986. CARDIA followed up participants for up to 28 years, and 94% of the surviving cohort completed at least 1 telephone interview or examination from August 2009 through August 2014. EXPOSURES: Blood pressures measubred at baseline (Y₀) and 15 years later (Y₁₅). MAIN OUTCOMES AND MEASURES: Composite CVD events, including coronary heart disease, stroke, heart failure, and other vascular diseases. RESULTS: A total of 4880 participants participated in the study (mean [SD] age, 24.9 [3.6] years at Y₀ and 25.0 [3.6] years at Y₁₅; 2223 male [45.6%] at Y₀ and 1800 [44.2%] at Y₁₅; 2657 female [54.4%] at Y₀ and 2277 [55.8%] at Y₀; 2473 black individuals [50.7%] at Y₀ and 1994 [48.9%] at Y₁₅; and 2407 white individuals [49.3%] at Y₀ and 2083 [51.1%] at Y₁₅). The mean SBP/DBP was 112/69 mm Hg in blacks and 109/68 mm Hg in whites at Y₀ and 117/77 mm Hg in blacks and 110/72 mm Hg in whites at Y₁₅. During a 25-year follow-up from Y₀, 210 CVD events occurred (twice as many events in blacks [n = 140] compared with whites), of which 131 (87 in blacks) occurred after Y₁₅. With adjustments for covariates, results from Cox proportional hazards models, including SBP and DBP, jointly suggested that, at Y₀, SBP (hazard ratio [HR] per 1-SD increase, 1.32; 95% CI, 1.09-1.61) but not DBP (HR, 1.05; 95% CI, 0.88-1.26) was associated with CVD risk in blacks, whereas DBP (HR, 1.74; 95% CI, 1.21-2.50) but not SBP (HR, 0.82; 95% CI, 0.57-1.18) was associated with CVD risk in whites. At Y_15, SBP was the strongest indicator of CVD in blacks (HR, 1.64; 95% CI, 1.25-2.16) and whites (HR, 1.67; 95% CI, 1.02-2.69). CONCLUSIONS AND RELEVANCE: This study questions the classic view that DBP is more able to identify future CVD events than SBP in all individuals younger than 50 years. In young adulthood, SBP in black individuals and DBP in white individuals were the most robust indicators of future CVD. In middle-age, SBP in both races identified risk of incident CVD.