The L-shaped association of mid-upper arm circumference with all-cause and cause-specific mortality in US adults: a population-based prospective cohort study

BACKGROUND: The arm circumference is a feasible and reliable indicator in evaluating the nutritional status of children. However, its application in general adults has yet to be thoroughly investigated. OBJECTIVE: This study aimed to evaluate the association between mid-upper arm circumferences (MUACs) and mortality in general adults. METHODS: The nationally representative cohort from the National Health and Nutrition Examination Survey (1999-2018) was analyzed with mortality information obtained through linkage to the National Death Index. The baseline MUACs were collected as exposure. Survey-weighted Cox proportional hazard regressions were performed to estimate the hazard ratios (HRs) and 95% confidential intervals (CIs) of mortality risk for individuals with different MUACs. Restricted cubic spline analyses were performed to examine the nonlinear association of MUAC with all-cause and cause-specific mortality. RESULTS: A total of 52,159 participants were included in this study. During a median follow-up time of 117 months, 7157 deaths were documented, with leading causes of cardiovascular disease (CVD), cancer, and respiratory disease. Individuals in the first quartile (Q1) of MUAC tended to have higher all-cause mortality risk than the rest after full adjustment. Similarly, CVD mortality risk in Q1 was higher than that in the second quartile (Q2) and the third quartile (Q3); respiratory mortality risk in Q1 was higher than in Q2. MUAC was non-linearly associated with all-cause mortality and CVD mortality. Individuals in Q1 MUAC (≤ 29.3) tended to have higher all-cause mortality risk, with HRs (95% CIs) estimated to be 0.76 (0.67-0.87) for Q2 (29.4, 32.5), 0.69 (0.59-0.81) for Q3 (32.6, 36.0), and 0.59 (0.46-0.75) for Q4 (≥ 36.1) after adjustment of demographic, lifestyle, and comorbidity covariates. Similarly, compared with Q1, HRs (95% CIs) for CVD mortality were estimated to be 0.73 (0.58-0.93) for Q2 and 0.57 (0.43-0.47) for Q3; HRs (95% CIs) for respiratory mortality was estimated to be 0.57 (95% CI, 0.37-0.87) for Q2 with other differences not significant. CONCLUSION: The MUAC was inversely associated with long-term mortality in general adults in the United States and may serve as a valuable measurement in adult health evaluations.