Supplementary Material for: The Healthy Ageing Questionnaire (HAQ) Index: Validation in the Singapore Longitudinal Ageing Study

Objective: 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. Study Design and Setting: 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 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.