Physical function mitigates the adverse effects of being thin on mortality in a free-living older Taiwanese cohort

To examine the significance of underweight and physical function as well as their interaction on mortality in the aged.

Prospective cohort.

The Elderly Nutrition and Health Survey in Taiwan during 1999-2000.

Total of 1435 representative free-living elders (739 men and 696 women).

Body composition was assessed by various anthropometrics. Physical function score (PF, ranged 0-100) was derived from the SF-36(®). Death by December 31, 2006 was the outcome measure.

After 7.9 (median: 7.0) years follow-up, 381 (223 men, 158 women) of 1435 eligible participants had died. Those with the lowest PF (<45) had 3.43 (hazards ratio (HR), 95% confidence interval (CI) = 2.20-5.36) times the all-cause mortality risk of the highest PF (≥58). Interactions for PF and BMI (P =0.02) and for PF and wrist circumference (P =0.09) on death were found after controlling for potential confounders. Jointly, compared to normal-BMI-highest-PF, the greatest HR for death occurred where BMI <18.5 kg/m2 was combined with the lowest-PF after covariate adjustments (HR = 8.67, 95% CI = 3.77-20.0). Similarly, the lowest arm muscle circumference (MAMC)-PF had a HR of 5.22 compared to mid-MAMC-highest-PF. However, percent and absolute body fat, estimated by bioelectrical impedance, was comparable to non-sarcopenic individuals.

Thin elderly Taiwanese with sarcopenia, and less skeleton, are at the most risk of death, especially if physical function is limited.