The predictive validity of the 10/66 dementia diagnosis in Chennai, India: a 3-year follow-up study of cases identified at baseline.

INTRODUCTION: The prevalence of dementia according to DSM-IV criteria tends to be very low in less developed settings. The 10/66 Dementia Research Group's cross-culturally validated diagnosis returns a considerably higher prevalence. Assessing the predictive validity of the 10/66 dementia diagnosis will assist in establishing the best criterion for estimating the population burden of dementia.
METHODS: In a population-based study in Chennai, India, we aimed to follow-up after 3 years 75 people with 10/66 dementia and 193 with cognitive impairment but no dementia (CIND), reassessing diagnostic status, clinical severity, cognitive function, disability, and needs for care.
RESULTS: We traced 54 people with dementia of whom 25 (46.3%) had died, double the mortality rate among those with CIND. Twenty-two of the 24 people with 10/66 dementia that were reexamined still met 10/66 dementia criteria. There was clear evidence of clinical progression and increased needs for care. Only one "case" had unambiguously improved. Cognitive function had deteriorated and disability increased to a much greater extent than among those with CIND.
CONCLUSION: The strong predictive validity of the 10/66 dementia diagnosis is consistent with a lack of sensitivity of the DSM-IV criteria to mild-to-moderate cases, which may underestimate prevalence in less developed regions.