New data challenge the obesity paradox with regard to CVD morbidity and longevity

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

Literature - Khan SS, Ning H, Wilkins JT, et al. - JAMA Cardiol 2018; published online ahead of print

Background

High body mass index (BMI) has been associated with similar or lower all-cause mortality rates compared with normal BMI, but the contribution of CVD to these results is not clear [1,2].

In this study, lifetime risk estimates of incident total CVD and subtypes of CVD, as well as years lived with and without CVD, were calculated by weight status.

Adults aged 20-89 years, without CVD at baseline, with available BMI and outcomes data, as well as a follow-up of at least 10 years, who were included in the Cardiovascular Disease Lifetime Risk Pooling Project [3] were eligible for the analysis, resulting into 190,672 person-examinations across the life course, with 3.2 million person-years of follow-up until 2015.

Participants were stratified by index age groups (young: 20-39 years, middle-aged: 40-59 years, older: 60-79 years), gender and BMI strata (underweight: <18.5), normal: 18.5-24.9, overweight: 25.0-29.9, obesity: 30.0-39.9, morbid obesity: ≥40). The non-fatal CVD events of interest included myocardial infarction (MI), stroke, and heart failure (HF), and fatal events were stratified as death caused by CVD, coronary heart disease (CHD), or non-CVD events.

Main results

Incident CVD events occurred in more middle-aged men and women in the overweight (37% and 28%, respectively), obese (47% and 39%), and morbidly obese (65% and 48%) strata compared with adults in the normal BMI group (32% and 22%).
Compared with normal BMI, middle-aged men and women who were overweight, obese, and morbidly obese had significantly higher HRs for incident CVD events (HR for overweight men: 1.21; 95%CI: 1.14-1.28; HR for overweight women: 1.32; 95%CI: 1.24-1.40; HR for obese men: 1.67; 95%CI: 1.55-1.79; HR for obese women: 1.85; 95%CI: 1.72-1.99; HR for morbidly obese men: 3.14; 95%CI: 2.48-3.97; HR for morbidly obese women: 2.53; 95%CI: 2.20-2.91).
The adjusted competing HRs of incident CVD events per unit of BMI in middle-aged men and women were 1.05 (95%CI: 1.05-1.06) and 1.05 (95%CI: 1.04-1.05), respectively.
In middle-aged men, overall survival time was similar in the normal BMI (29.1 years) and overweight (29.3 years) groups, and was significantly shorter in the obese (27.2 years) and morbidly obese (23.4 years) groups.
In middle-aged women, overall survival was longest in the normal BMI category (33.2 years) compared with women in higher BMI categories (overweight: 31.8 years; obese: 29.8 years; and morbidly obese: 27.2).
Average years lived with CVD in middle-aged men and women were shortest in the normal BMI group compared to individuals in the higher BMI groups, resulting in relative compression of CV morbidity. Normal BMI significantly delayed incidence of CVD in middle-aged men and women by 7.5 and 7.1 years, respectively, compared with morbid obesity.
For all findings, similar patterns were seen in younger and older men and women.

Conclusion

Overweight and obese individuals have a significantly increased long-term risk for CVD morbidity, a similar or shorter total longevity, and a greater proportion of life lived with morbidity compared with individuals with a normal BMI. These findings challenge the view that overweight is associated with greater longevity compared with normal BMI.

References

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