Association of Body Mass Index With Lifetime Risk of Cardiovascular Disease and Compression of Morbidity

Abstract

Importance: Prior studies have demonstrated lower all-cause mortality in individuals who are overweight compared with those with normal body mass index (BMI), but whether this may come at the cost of greater burden of cardiovascular disease (CVD) is unknown.

Objective: To calculate lifetime risk estimates of incident CVD and subtypes of CVD and to estimate years lived with and without CVD by weight status.

Design, setting, and participants: In this population-based study, we used pooled individual-level data from adults (baseline age, 20-39, 40-59, and 60-79 years) across 10 large US prospective cohorts, with 3.2 million person-years of follow-up from 1964 to 2015. All participants were free of clinical CVD at baseline with available BMI index and CVD outcomes data. Data were analyzed from October 2016 to July 2017.

Exposures: World Health Organization-standardized BMI categories.

Main outcomes and measures: Total CVD and CVD subtype, including fatal and nonfatal coronary heart disease, stroke, congestive heart failure, and other CVD deaths. Heights and weights were measured directly by investigators in each study, and BMI was calculated as weight in kilograms divided by height in meters squared. We performed (1) modified Kaplan-Meier analysis to estimate lifetime risks, (2) adjusted competing Cox models to estimate joint cumulative risks for CVD or noncardiovascular death, and (3) the Irwin restricted mean to estimate years lived free of and with CVD.

Results: Of the 190 672 in-person examinations included in this study, the mean (SD) age was 46.0 (15.0) years for men and 58.7 (12.9) years for women, and 140 835 patients (73.9%) were female. Compared with individuals with a normal BMI (defined as a BMI of 18.5 to 24.9), lifetime risks for incident CVD were higher in middle-aged adults in the overweight and obese groups. Compared with normal weight, among middle-aged men and women, competing hazard ratios for incident CVD were 1.21 (95% CI, 1.14-1.28) and 1.32 (95% CI, 1.24-1.40), respectively, for overweight (BMI, 25.0-29.9), 1.67 (95% CI, 1.55-1.79) and 1.85 (95% CI, 1.72-1.99) for obesity (BMI, 30.0-39.9), and 3.14 (95% CI, 2.48-3.97) and 2.53 (95% CI, 2.20-2.91) for morbid obesity (BMI, ≥40.0). Higher BMI had the strongest association with incident heart failure among CVD subtypes. Average years lived with CVD were longer for middle-aged adults in the overweight and obese groups compared with adults in the normal BMI group. Similar patterns were observed in younger and older adults.

Conclusions and relevance: In this study, obesity was associated with shorter longevity and significantly increased risk of cardiovascular morbidity and mortality compared with normal BMI. Despite similar longevity compared with normal BMI, overweight was associated with significantly increased risk of developing CVD at an earlier age, resulting in a greater proportion of life lived with CVD morbidity.

Figure 1.. Lifetime Risk of Cardiovascular Disease (CVD) Morbidity and Mortality Among Middle-aged Individuals

Remaining cumulative lifetime risk estimates for total CVD events (adjusted for competing risk of noncardiovascular death) in middle-aged (index age, 40-59 years) men (A) and women (B) stratified by body mass index groups: underweight, normal, overweight, obese, and morbidly obese. Lifetime risks for total cardiovascular disease exceeded 30% for men and women in all body mass index groups. Participants in higher body mass index strata had higher lifetime risks for total cardiovascular disease through age 95 years.

Figure 2.. Years Lived Free of and With Cardiovascular Disease (CVD) Among Middle-aged Individuals

Years lived free of and with CVD in middle-aged (index age, 40-59 years) men (A) and women (B). Participants with normal body mass index experienced greater years lived free of CVD compared with participants who were underweight, overweight, obese, or morbidly obese. Years lived with CVD was greater in participants in higher body mass index groups, accounting for a greater degree of life lived with morbidity in the context of similar or shorter overall survival. Compared with men and women with normal body mass index, men and women with morbid obesity had an accelerated onset of CVD by 7.5 and 7.1 years, respectively, and had reduced overall survival by 5.6 and 2.0 years.