Association of young adult cardiometabolic risk factors on premature mortality

Introduction Cardiometabolic risk factors are a major contributor to mortality globally. While there has been substantial research estimating the risk of increased BMI, HbA1c, systolic blood pressure and non-HDL cholesterol in middle-aged and elderly people, with the increasing prevalence of these risk factors among younger adults in recent decades there is a correspondent need to better understand their impacts on this population. Methods Using a sample of the 1988-1994 NHANES III survey linked to National Death Index records through 2019 we conducted a multivariable Cox regression on standardized cardiometabolic variables to assess the relative hazard of each variable on the risk of early mortality at or before age 65 per standard deviation increase. Analyses were stratified into young adults (18-39), forties (40-49), and fifties (50-59) to examine how the relative impact of these variables changes across early and middle adulthood. Results Higher BMI (HR 1.20 per standard deviation increase, 95% CI 1.06 to 1.35), HbA1c (HR 1.17, 95% CI 1.07-1.27) and number of cigarettes smoked (HR 1.07, 95% CI 1.02-1.12) were associated with higher early mortality. When stratified into age groups BMI was the strongest risk factor for early mortality in young adults (HR = 1.25, 95%CI 1.07-1.47), whereas HbA1c was most associated with mortality risk for people in their 40s (HR = 1.33, 95%CI 1.14-1.54), and number of lifetime cigarettes smoked for people in their 50s (HR = 1.24, 95%CI 1.14-1.34). Conclusions Greater BMI, HbA1c, and lifetime cigarettes were associated with an increased risk of early mortality. When stratified by age, the predominate risk factor shifted from higher BMI in young adults, to HbA1c in people in their forties, to number of lifetime cigarettes for people in their fifties, providing evidence that the relative importance of well-established cardiometabolic risk factors evolve over the life course. Key messages • Cardiometabolic risk factors magnitudes of association shift across the life-course indicating that controlling obesity in young adulthood may have even greater importance than previously recognised. • Increased risk of early mortality associated with increasing HbA1c percent in the fifth decade of life may have implications for improving glucose control as people reach middle-adulthood.