Three-year weight change and risk of all-cause, cardiovascular, and cancer mortality among Iranian adults: over a decade of follow-up in the Tehran Lipid and Glucose Study

Background We investigated the impact of weight change on mortality in a population-based cohort setting. Methods We conducted two weight measurements for 5436 participants aged >= 30 years with an approximate 3-year interval. Based on their weight change, we categorized participants to: > 5% weight loss, 3-5% weight loss, stable weight (+/- < 3%), 3-5% weight gain, > 5% weight gain. We followed participants for mortality annually up to March 20th 2018. We applied the multivariable Cox proportional hazard models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of weight change categories for all-cause, cardiovascular (CV), and cancer mortality, considering stable weight as reference. The Cox models was adjusted for age, sex, educational level, body mass index, smoking status, hypertension, hypercholesterolemia, diabetes, and cardiovascular disease (CVD) at baseline. Results During a median follow-up of 14.4 years, 629 deaths (247 CV and 126 cancer deaths) have occurred. Over 5% weight loss and gain were associated with increased risk of all-cause mortality in multivariable analysis with HRs of 1.47 [95% CI: 1.17-1.85] and 1.27 [1.02-1.57], respectively; however, a 3-5% loss or gain did not alter the risk of all-cause mortality significantly. These significant risks for wight change > 5% were not modified by the presence of diabetes, obesity, and smoking status; however, the unfavorable impact of weight change on mortality events was more prominent in those older than > 65 years (P-value for interaction: 0.042). After excluding those with history of CVD, diabetes, and cancer during the weight measurements period, these associations significantly attenuated (HR: 1.29 [0.89-1.87] for > 5% weight loss and 1.12 [0.84-1.50] for > 5% weight gain). Additionally, a > 5% weight loss was also associated with about 60% higher risk for CV mortality (HR: 1.62 [1.15-2.28]), and a 3-5% weight loss was associated with about 95% higher risk of cancer mortality (HR: 1.95 [1.13-3.38]). Conclusions Our findings showed a U-shaped association across weight change categories for all-cause mortality risk with over 5% weight gain and loss causing higher risk. Moreover, weight loss can have adverse impact on CV and cancer mortality events.