The long-term prognosis of cardiovascular disease and all-cause mortality for metabolically healthy obesity: a systematic review and meta-analysis

Background Metabolically healthy obese phenotype (MHO) refers to obese individuals with absence of metabolic abnormalities such as dyslipidaemia, insulin resistance and hypertension. Many studies reported the long-term prognosis of MHO on diseases and mortality with inconsistent results. Methods We performed a meta-analysis to assess the risks of cardiovascular (CV) events and all-cause mortality for MHO individuals. Original prospective observational studies were searched in Medline, EMBASE, Web of Science and Cochrane library up to 30 September 2015. In this meta-analysis, the relative risk (RR) calculated on the basis of the incident number of disease events and deaths in participants and the corresponding multivariable-adjusted HR were both extracted to calculate pooled risk estimates. A random-effects model was used if there was heterogeneity among studies; otherwise, the fixed-effects model was used. Results 22 prospective studies, involving 584 799 participants, were archived in the analyses. With metabolically healthy normal weight as the reference, the MHO phenotype was associated with a higher risk of CV events (RR 1.50, 95% CI 1.27 to 1.77; HR 1.60, 95% CI 1.38 to 1.84). However, MHO individuals were not associated with increased risk of all-cause mortality (RR 1.18, 95% CI 0.83 to 1.66; HR 1.07, 95% CI 0.92 to 1.25). Conclusions The meta-analysis confirms a positive association between a metabolically healthy obese phenotype and the risk of CV events. However, higher risk for all-cause mortality is not evident in metabolically healthy obese individuals.