Calf circumference is an independent predictor of mortality in older adults: An approach with generalized additive models

Abstract

Background: There is a wide variation in the cutoff points of body mass index (BMI) and calf circumference (CC) , and it is necessary to assess their adequacy in predicting mortality, especially in the older adults in the community. This study aimed to investigate the association of low muscle mass and underweight with mortality in older adults, comparing different cutoff points.

Methods: This was a prospective study that included 796 older adults, not institutionalized, from a Brazilian city. Generalized additive models (GAMs) were used to identify cutoff points for CC and BMI, which were compared with values available in the literature. Survival analysis using Cox regression models was used to assess the independent association between these nutrition indicators and mortality.

Results: Over the 9 years of follow-up, 197 deaths (24.7%) occurred. Cutoff points established for CC and BMI as predictors of mortality were, respectively, <34.5 cm and <24.5. In the adjusted Cox models, older adults with a BMI <18.5 showed a significant increase in the risk of death (hazard ratio [HR], 2.57; 95% CI, 1.23-5.35). Higher mortality was observed among older adults with CC <34.5 cm (HR, 1.72; 95% CI, 1.27-2.33) and CC <31 cm (HR, 2.11; 95% CI, 1.44-3.10).

Conclusion: CC was an independent predictor of mortality, and the cutoff point identified by GAMs was higher than recommended by literature (31 cm). This study suggests a review of cutoff points for CC currently adopted to assess low muscle mass in older adults.

Keywords: aging; body mass index; calf circumference; malnutrition; mortality; older adults.