Age moderates the relationships between obesity, glucose variability, and intensive care unit mortality: a retrospective cohort study

BACKGROUND: Although the associations between obesity, glucose variability (GV), and Intensive Care Unit (ICU) mortality have been studied extensively, whether age moderates these associations is not well understood. MATERIALS AND METHODS: The medical records of 1062 patients, who were admitted into ICU at Sir Run Run Shaw Hospital (Zhejiang, China), were studied. Logistic regression was used to test the associations between obesity, GV, and ICU mortality. Furthermore, the moderation effect of age was tested. RESULTS: After controlling for covariates, the underweight group had the highest odds of death (OR 2.38, 95% CI 1.43–3.95, p < 0.001) in comparison with the control group (overweight). However, normal weight (OR 1.29, 95% CI 0.88–1.89, p = 0.185) and obese (OR 1.08, 95% CI 0.61–1.90, p = 0.790) groups had similar odds of death, compared to the overweight group. Age significantly moderated the association between obesity and mortality, where being overweight was more advantageous than being normal weight in older adults (B = 0.03, SE = 0.01, OR 1.03, 95% CI 1.001–1.06, p = 0.045). Meanwhile, higher GV predicted greater mortality in adjusted models (OR 1.23, 95% CI 1.06–1.42, p = 0.005). We also found an interaction between age and GV (B = − 0.01, SE = 0.01, OR 0.99, 95% CI 0.98–0.999, p = 0.025), which suggested that the association between GV and mortality becomes weaker with increasing age. CONCLUSIONS: With increasing age, the association between BMI and mortality becomes stronger and the association between glucose variability and mortality becomes weaker. Future studies should investigate the underlying mechanisms of such phenomenon and the causal relationship between obesity, GV, and ICU mortality. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40560-021-00582-4.