The Healthy Ageing Questionnaire (HAQ) 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 (SLAS2). Its construct, concurrent and predictive validity was evaluated in 2161 participants in the SLAS2 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 MMSE 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 increased mortality risks from 40.6 to 9.7 deaths per 1,000 p-y; covariate-adjusted hazard ratio for the highest Q5 levels (HAQ score >70) was 0.44 (95%CI=0.28-0.67). Using ROC analysis of predictive accuracy for survival, the AUC 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.