BACKGROUND:
Although tooth loss is known to increase the risk of cognitive impairment and dementia, few studies have investigated the association between functional teeth including rehabilitated lost teeth and cognitive functionObjective:We investigated the associations of the numbers of functional teeth and functional occlusal units with cognitive impairment and cognitive function in late life.

METHODS:
The current study was conducted as a part of the Korean Longitudinal Study on Cognitive Aging and Dementia (KLOSCAD), a community-based elderly cohort study. We analyzed 411 participants who have agreed with the additional dental exam. Geriatric psychiatrists and neuropsychologists administered the Consortium to Establish a Registry for Alzheimer's disease Assessment Packet Clinical and Neuropsychological Assessment Battery to all participants, and dentists examined their dental status.

RESULTS:
Higher number of functional teeth (OR = 0.955, 95% CI = 0.914-0.997, p = 0.037) and higher number of functional occlusal units (OR = 0.900, 95% CI = 0.813-0.996, p = 0.042) were associated with lower odds of cognitive impairment. When we analyzed these relationships separated by the location of teeth, only the numbers of functional teeth (OR = 0.566, 95% CI = 0.373-0.857, p = 0.007) and functional occlusal units (OR = 0.399, 95% CI = 0.213-0.748, p = 0.004) in the premolar area were associated with lower odds of cognitive impairment.

CONCLUSION:
Loss of functional teeth and functional occlusal units (especially in the premolar region) were associated with increased cognitive impairment.