Association between Body Mass Index and Mortality in Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis.

Background: The association between body mass index (BMI) and mortality in patients with type 1 diabetes mellitus (T1DM) has been poorly examined and has never been systematically reviewed. This meta-analysis investigated the all-cause mortality risk for each BMI category among patients with T1DM.

Methods: A systematic literature review of the PubMed, Embase, and Cochrane Library databases was performed in July 2022. Cohort studies comparing the mortality risk between BMI categories among patients with T1DM were eligible. Pooled hazard ratios (HRs) for all-cause mortality among underweight (BMI <18.5 kg/m²), overweight (BMI, 25 to <30 kg/m²), and obese (BMI ≥30 kg/m²) individuals were calculated in reference to the normal-weight group (BMI, 18.5 to <25 kg/m²). The Newcastle-Ottawa Scale was used to assess the risk of bias.

Results: Three prospective studies involving 23,407 adults were included. The underweight group was shown to have a 3.4 times greater risk of mortality than the normal-weight group (95% confidence interval [CI], 1.67 to 6.85). Meanwhile, there was no significant difference in mortality risk between the normal-weight group and the overweight group (HR, 0.90; 95% CI, 0.66 to 1.22) or the obese group (HR, 1.36; 95% CI, 0.86 to 2.15), possibly due to the heterogeneous results of these BMI categories among the included studies.

Conclusion: Underweight patients with T1DM had a significantly greater risk of all-cause mortality than their normal-weight counterparts. Overweight and obese patients showed heterogeneous risks across the studies. Further prospective studies on patients with T1DM are required to establish weight management guidelines.