Abstract
Aims/hypothesisThe relationship between BMI and mortality has been extensively investigated in the general population; however, it is less clear in people with type 2 diabetes. We aimed to assess the association of BMI with all-cause and cardiovascular mortality in individuals with type 2 diabetes mellitus.MethodsWe searched electronic databases up to 1 March 2016 for prospective studies reporting associations for three or more BMI groups with all-cause and cardiovascular mortality in individuals with type 2 diabetes mellitus. Study-specific associations between BMI and the most-adjusted RR were estimated using restricted cubic splines and a generalised least squares method before pooling study estimates with a multivariate random-effects meta-analysis.ResultsWe included 21 studies including 24 cohorts, 414,587 participants, 61,889 all-cause and 4470 cardiovascular incident deaths; follow-up ranged from 2.7 to 15.9 years. There was a strong nonlinear relationship between BMI and all-cause mortality in both men and women, with the lowest estimated risk from 31–35 kg/m2 and 28–31 kg/m2 (p value for nonlinearity <0.001) respectively. The risk of mortality at higher BMI values increased significantly only in women, whilst lower values were associated with higher mortality in both sexes. Limited data for cardiovascular mortality were available, with a possible inverse linear association with BMI (higher risk for BMI <27 kg/m2).Conclusions/interpretationIn type 2 diabetes, BMI is nonlinearly associated with all-cause mortality with lowest risk in the overweight group in both men and women. Further research is needed to clarify the relationship with cardiovascular mortality and assess causality and sex differences.
Highlights
Electronic supplementary material The online version of this article contains peer-reviewed but unedited supplementary material, which is available to authorised users.Compared with the general population, diabetes mellitus is associated with a higher mortality, mainly attributable to cardiovascular causes [1]
All but three studies adjusted for age and sex and diagnosis of diabetes was mainly
Cardiovascular disease mortality 7 studies | 7 cohorts similar in sensitivity analyses considering alternative knot locations (ESM Fig. 7 and ESM Fig. 8). Results of this meta-analysis indicate a clear nonlinear relationship between BMI and all-cause mortality, with the lowest risk found around 33 kg/m2 and an increased risk more evident for lower compared with higher values
Summary
Electronic supplementary material The online version of this article (doi:10.1007/s00125-016-4162-6) contains peer-reviewed but unedited supplementary material, which is available to authorised users.Compared with the general population, diabetes mellitus is associated with a higher mortality, mainly attributable to cardiovascular causes [1]. A recent systematic review including nine studies reported a reduced risk of all-cause mortality in overweight and obese people with type 2 diabetes when compared with normal or non-overweight people and a 5% progressive decrease in mortality for every 5 kg/m2 increase in BMI [13]. This analysis, did not explore whether a nonlinear relationship exists between BMI and outcomes. A clearer determination of the relationship across BMI values would elucidate the comparative relevance of higher and lower BMI values on mortality risk in people with diabetes
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