2.1. Study Population and Study Design

This is a comparative study, as part of a larger population based on a longitudinal study, which investigates neuroprotection model for the purpose of healthy longevity among Malaysian elderly, namely towards useful aging (TUA). The methodology of this study was described earlier [19]. Briefly, subjects were chosen using multi-stage random sampling method from states with the highest prevalence (at least 10% from the total population of the state) of elderly according to each zone in Peninsular Malaysia; Perak (North), Selangor (Central), Kelantan (East), and Johor (South). This study was divided into three phases. Phase 1 and 2 have been described earlier [13,20]. The study protocol was approved by the Research and Medical Research Ethics Committee of University Kebangsaan Malaysia (UKM), and informed consent was obtained from all participants.