Background. With the rapid worldwide increase in the oldest old population, considerable concern has arisen about the social and economic burden of diseases and disability in this age group. Understanding of multidimensional structure of health and its life-course trajectory is an essential prerequisite for effective health care delivery. Therefore, we organized an interdisciplinary research team consisting of geriatricians, dentists, psychologists, sociologists, and epidemiologists to conduct a longitudinal observational study. Methods/Design. For the Tokyo Oldest Old Survey on Total Health (TOOTH) study, a random sample of inhabitants of the city of Tokyo, aged 85 years or older, was drawn from the basic city registry. The baseline comprehensive assessment consists of an in-home interview, a self-administered questionnaire, and a medical/dental examination. To perform a wide variety of biomedical measurements, including carotid ultrasonography and a detailed dental examination, participants were invited to our study center at Keio University Hospital. For those who were not able to visit the study center, we provided the option of a home-based examination, in which participants were simultaneously visited by a geriatrician and a dentist. Of 2875 eligible individuals, a total of 1152 people were recruited, of which 542 completed both the in-home interview and the medical/dental examination, with 442 completed the in-home interview only, and another 168 completed self or proxy-administered data collection only. Carotid ultrasonography was completed in 458 subjects, which was 99.6% of the clinic visitors (n = 460). Masticatory assessment using a colour-changeable chewing gum was completed in 421 subjects, a 91.5% of the clinic visitors. Discussion. Our results demonstrated the feasibility of a new comprehensive study that incorporated non-invasive measurements of subclinical diseases and a detailed dental examination aiming at community-dwelling individuals aged 85 years or older. The bimodal recruitment strategy is critically important to capture a broad range of health profiles among the oldest old. Results form the TOOTH study will help develop new models of health promotion, which are expected to contribute to an improvement in lifelong health and well-being. Trial Registration. This study has been registered in the UMIN-Clinical Trial Registry (CTR), ID: UMIN000001842.
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