Verification of Reported Age of Centenarians in Thailand

The objectives of this study were to verify the number of Thai centenarians based on the Thai population registration database and to study the causes for an upward bias of age reporting among centenarians. A phone-based sample survey was conducted with key informants to compare registration data with the de facto number of living centenarians. A sample of presumed centenarians in a sub-set of Thailand’s 76 provinces was selected to confirm the existence of the centenarians, along with their age, and to explain any discrepancies with registration data. This study found that among 358 recorded centenarians, only 53 (15%) were found to be still alive at the time of data collection. Among those who were still alive, 45 were contacted in person, with only 20 (44.4%) confirmed to be centenarians (i.e., age of 100 years or older). Older persons tend to misreport their age, usually with an upward bias, or the inaccuracy could be from an erroneous entry of the date on the birth certificate or household registration book. Furthermore, nonnotification of death was the leading reason for not discharging deceased persons from registration data, thus contributing to an over-count of living centenarians. Based on the findings of this study, the authors provide recommendations for improving the quality of the population registration data, especially for Thailand’s centenarians, and guidelines for future related research.