The present study examined the dose–response association of body mass index (BMI) and risk of all-cause and cardiovascular mortality in patients with existing hypertension.

A systematic search was done using PubMed and Scopus, from their inception up to January 25, 2017. Prospective and retrospective cohort studies reporting risk estimates of all-cause and cardiovascular mortality for three or more quantitative categories of BMI were included. Studies which reported results as continuous also were included. Pooled relative risks (RRs) were calculated using random effects models.

Of initial 34,938 identified studies, 14 studies with a total of 489,222 hypertensive patients, involving 41,872 cases of all-cause mortality and 2,123 cases of cardiovascular mortality were included. A five-unit increment in BMI was associated with an 8% reduction in the risk of all-cause mortality (Pooled RR: 0.92, 95% CI: 0.87, 0.97, P=0.003; I²=95.7%, n=13), and marginally and inversely associated with the risk of cardiovascular mortality (Pooled RR: 0.95, 95% CI: 0.88, 1.02, P=0.15; I²=90.3%, n=5). Nonlinear dose–response meta-analysis suggested a reverse J-shaped association between BMI and risk of all-cause and cardiovascular mortality, with a nadir at BMI of ∼27.5–30kg/m². Subgroup analysis indicated that the strength and shape of the association between BMI and all-cause mortality might be influenced by age.

There is strong evidence which confirms existence of obesity paradox in patients with hypertension. However, owing to the observational nature of included studies, these findings should be interpreted with caution.