Abstract
OBJECTIVES: To systematically review longitudinal studies examining the association between oral health and cognitive decline. DESIGN: Studies published between January 1993 and March 2013 were identified by search of English language publications in PubMed/Medline using relevant Medical Subject Heading terms and title and abstract keywords and from CINAHL using relevant subject headings. After applying eligibility criteria and adding four studies identified from article references, 56 of the 1,412 articles identified remained; 40 were cross-sectional, and 16 were longitudinal; 11 of the latter examined the effect of oral health on change in cognitive health or dementia incidence, five examined the reverse. SETTING: Sources of information included administrative data, subject evaluations in parent studies, medical and dental records, self-reports, and in-person evaluations. PARTICIPANTS: Older adults. MEASUREMENTS: Most studies used subjects whose oral or cognitive status was known, using standard approaches to impute for missing information. The oral health information most frequently studied included number of teeth, periodontal and caries problems, and denture use. Cognition was most frequently evaluated using the Mini-Mental State Examination or according to a diagnosis of dementia. RESULTS: Some studies found that oral health measures such as number of teeth and periodontal disease were associated with risk of cognitive decline or incident dementia, whereas others did not find an association. Similarly, cognitive decline was not consistently associated with greater loss of teeth or number of decayed teeth. It is likely that methodological limitations play a major role in explaining the inconsistent findings. CONCLUSION: It is unclear how or whether oral health and cognitive status are related. Additional research is needed in which there is greater agreement on how oral health and cognitive states are assessed to better examine the linkages between these two health outcomes.