Frailty in the Honolulu-Asia Aging Study: deficit accumulation in a male cohort followed to 90% mortality

Abstract

Background: A frailty index (FI) based on the accumulation of deficits typically has a submaximal limit at about 0.70. The objectives of this study were to examine how population characteristics of the FI change in the Honolulu-Asia Aging Study cohort, which has been followed to near-complete mortality. In particular, we were interested to see if the limit was exceeded.

Methods: Secondary analysis of six waves of the Honolulu-Asia Aging Study. Men (n = 3,801) aged 71-93 years at baseline (1991) were followed until death (N = 3,455; 90.9%) or July 2012. FIs were calculated across six waves and the distribution at each wave was evaluated. Kaplan-Meier analyses and Cox proportional hazard models were performed to examine the relationship of frailty with mortality.

Results: At each wave, frailty was nonlinearly associated with age, with acceleration in later years. The distributions of the FIs were skewed with long right tails. Despite the increasing mortality in each successive wave, the 99% submaximal limit never exceeded 0.65. The risk of death increased with increasing values of the FI (eg, the hazard rate increased by 1.44 [95% CI = 1.39-1.49] with each increment in the baseline FI grouping). Depending on the wave, the median survival of people with FI more than 0.5 ranged 0.84-2.04 years.

Conclusions: Even in a study population followed to almost complete mortality, the limit to deficit accumulation did not exceed 0.65, confirming a quantifiable, maximum number of health deficits that older men can tolerate.

Keywords: Deficit accumulation; Epidemiology; Frailty; Frailty index; Mortality..

Figure 1.

(A) Average frailty index by age pooling across six waves of the Honolulu-Asia Aging Study with standard error bars. (B) Proportional distributions of the frailty index for each of the six waves.

Figure 2.

Kaplan–Meier survival curves at varying levels of baseline frailty index in the Honolulu-Asia Aging Study. From top line to bottom: FI ≤ 0.05; 0.05 < FI ≤0.15; 0.15 < FI ≤ 0.25; 0.25 < FI ≤ 0.35; 0.35 < FI ≤ 0.50; FI > 0.50. FI = frailty index.