Context: The relationship between body mass index (BMI) and mortality may differ between patients with type 1 diabetes and the general population; it is not known which clinical characteristics modify the relationship.
Objective: Our aim was to assess the relationship between BMI and mortality and the interaction with clinically meaningful factors.
Design, setting, and participants: This prospective study included 5836 individuals with type 1 diabetes from the FinnDiane study.
Main outcome measure and methods: We retrieved death data for all participants on 31 December 2015. We estimated the effect of BMI on the risk of mortality using a Cox proportional hazards model with BMI as a restricted cubic spline as well as effect modification by adding interaction terms to the spline.
Results: During a median of 13.7 years, 876 individuals died. The relationship between baseline BMI and all-cause mortality was reverse J-shaped. When analyses were restricted to those with normal albumin excretion rate, the relationship was U-shaped. The nadir BMI (BMI with the lowest mortality) was in the normal weight region (24.3 to 24.8 kg/m2); however, among individuals with diabetic nephropathy, the nadir BMI was in the overweight region (25.9 to 26.1 kg/m2). Diabetic nephropathy, diabetes-onset age, and sex modified the relationship between BMI and mortality (Pinteraction < 0.05).
Conclusions: Normal weight is optimal for individuals with type 1 diabetes to delay mortality, whereas underweight might be an indication of underlying complications. Maintaining normal weight may translate into reduced risk of mortality in type 1 diabetes, particularly for individuals of male sex, later diabetes-onset age, and normal albumin excretion rate.
Copyright © 2019 Endocrine Society.