The Healthy Ageing Questionnaire Index: Validation in the Singapore Longitudinal Ageing Study.

Introduction: Healthy ageing (HA) indices typically use full questionnaire, performance- or blood-based assessment of functional ability which are time-consuming and resource-intensive. We developed and validated a simple and brief Healthy Ageing Questionnaire (HAQ) index with comparable measurement accuracy.

Methods: The 15-item HAQ (scored 0-100) was developed using data of 500 participants in the Singapore Study of Successful Ageing (SSOSA), a sub-cohort of the Singapore Longitudinal Ageing Study (SLAS-2). Its construct, concurrent, and predictive validity were evaluated in 2,161 participants in the SLAS-2 who were non-participants of the SSOSA.

Results: The HAQ index (mean = 64.0, SD = 11.8) showed a coherent 3-factor structure (Cronbach's alpha = 0.735). HAQ scores were higher among participants who were female, highly educated, not living alone, non-smoking, non-alcohol drinkers, not at risk of malnutrition, were robust or pre-frail, not disabled, had no or <5 medical conditions, and no recent fall or hospitalization. It was positively correlated with Mini-Mental State Examination and life satisfaction, and negatively correlated with age, logMAR vision, 5 times sit-and-stand, and timed-up-and-go. The HAQ index was significantly correlated but showed modest concordance with the Rowe-Kahn SA index. Increasing HAQ index quintiles were associated with decreased mortality risks from 40.6 to 9.7 deaths per 1,000 person-years; covariate-adjusted hazard ratio for the highest Q5 levels (HAQ score >70) was 0.44 (95% CI = 0.28-0.67). Using receiver operating characteristics analysis of predictive accuracy for survival, the area under the curve of HAQ was 0.675, and Rowe-Kahn SA index was 0.660 (p = 0.361).

Conclusion: The HAQ is a brief and accurate HA index that is potentially useful across diverse settings and purposes in research, healthcare, and policy-making.