The joint effects of frailty and telomere length for predicting mortality in older adults: the National Health and Nutrition Examination Survey 1999-2002.

BACKGROUND: Frailty and short telomere length, which address different aspects of biological aging, are separately associated with mortality in older adults. AIMS: To evaluate whether the combination of these two biomarkers would be a better predictor of mortality than either alone. METHODS: This present study included participants 60 years of age or older from the National Health and Nutrition Examination Survey in the 1999-2002 phase. The frailty phenotype was identified based on the Fried definition. Telomere length relative to standard reference DNA (T/S ratio) was assessed using quantitative polymerase chain reaction (PCR). Cox proportional hazards regression models were used to estimate the individual and combined effects of frailty phenotype and telomere length on all-cause and cardiovascular mortality. RESULTS: Compared with participants with neither impairment, the mortality risks increased slightly among participants with short telomere length only (hazard ratio [HR] 1.19, 95% confidence interval [CI]: 1.00-1.42) or pre-frailty only (HR 2.16, 95% CI 1.80-2.60) and gradually elevated approximately 3 folds with both short telomere length and pre-frailty (HR 2.23, 95% CI 1.81-2.74) or frailty (HR 3.57, 95% CI 2.56-4.98). Moreover, participants with both short telomere length and frailty had the highest increased all-cause mortality (HR 5.16, 95% CI 3.38-7.85) and cardiovascular mortality (HR 4.67, 95% CI 2.02-10.82). DISCUSSION AND CONCLUSIONS: The combined predictor had more capability of predicting mortality, which suggested that integrating both molecular biomarkers and physiological functional parameters would be a more informative measure of biological aging.