A comparison over 2 decades of disability-free life expectancy at age 65 years for those with long-term conditions in England: Analysis of the 2 longitudinal Cognitive Function and Ageing Studies

Abstract

Background: Previous research has examined the improvements in healthy years if different health conditions are eliminated, but often with cross-sectional data, or for a limited number of conditions. We used longitudinal data to estimate disability-free life expectancy (DFLE) trends for older people with a broad number of health conditions, identify the conditions that would result in the greatest improvement in DFLE, and describe the contribution of the underlying transitions.

Methods and findings: The Cognitive Function and Ageing Studies (CFAS I and II) are both large population-based studies of those aged 65 years or over in England with identical sampling strategies (CFAS I response 81.7%, N = 7,635; CFAS II response 54.7%, N = 7,762). CFAS I baseline interviews were conducted in 1991 to 1993 and CFAS II baseline interviews in 2008 to 2011, both with 2 years of follow-up. Disability was measured using the modified Townsend activities of daily living scale. Long-term conditions (LTCs-arthritis, cognitive impairment, coronary heart disease (CHD), diabetes, hearing difficulties, peripheral vascular disease (PVD), respiratory difficulties, stroke, and vision impairment) were self-reported. Multistate models estimated life expectancy (LE) and DFLE, stratified by sex and study and adjusted for age. DFLE was estimated from the transitions between disability-free and disability states at the baseline and 2-year follow-up interviews, and LE was estimated from mortality transitions up to 4.5 years after baseline. In CFAS I, 60.8% were women and average age was 75.6 years; in CFAS II, 56.1% were women and average age was 76.4 years. Cognitive impairment was the only LTC whose prevalence decreased over time (odds ratio: 0.6, 95% confidence interval (CI): 0.5 to 0.6, p < 0.001), and where the percentage of remaining years at age 65 years spent disability-free decreased for men (difference CFAS II-CFAS I: -3.6%, 95% CI: -8.2 to 1.0, p = 0.12) and women (difference CFAS II-CFAS I: -3.9%, 95% CI: -7.6 to 0.0, p = 0.04) with the LTC. For men and women with any other LTC, DFLE improved or remained similar. For women with CHD, years with disability decreased (-0.8 years, 95% CI: -3.1 to 1.6, p = 0.50) and DFLE increased (2.7 years, 95% CI: 0.7 to 4.7, p = 0.008), stemming from a reduction in the risk of incident disability (relative risk ratio: 0.6, 95% CI: 0.4 to 0.8, p = 0.004). The main limitations of the study were the self-report of health conditions and the response rate. However, inverse probability weights for baseline nonresponse and longitudinal attrition were used to ensure population representativeness.

Conclusions: In this study, we observed improvements to DFLE between 1991 and 2011 despite the presence of most health conditions we considered. Attention needs to be paid to support and care for people with cognitive impairment who had different outcomes to those with physical health conditions.

Fig 1

DFLE and DLE at age 65 years for men (A) and women (B) with a health condition in the CFAS I and CFAS II. Models stratified by sex and study and adjusted for age and the health condition. Results also shown in Tables C and E in S5 Text with 95% CIs and p-values. CFAS, Cognitive Function and Ageing Study; DFLE, disability-free life expectancy; DLE, life expectancy with disability.

Fig 2. RRR of transitioning between disability states in the CFAS II (2011) compared to CFAS I (1991) for men and women with each LTC with 95% CI.

Estimates from models stratified by sex and health condition with age and study covariates. Results also shown in Table 3 with 95% CI and p-values. CFAS, Cognitive Function and Ageing Studies; CI, confidence interval; RRR, relative risk ratio; LTC, long-term condition.

Fig 3

Difference in years with disability (DLE) between men (A) and women (B) with and without the health condition (DLE without health condition–DLE with health condition) in CFAS II with 95% CIs. Models stratified by sex and study and adjusted for age and health condition. Results also shown in Tables C and E in S5 Text with 95% CIs and p-values. CFAS, Cognitive Function and Ageing Studies; CI, confidence interval; DLE, life expectancy with disability.