AbstractAimTo evaluate whether tooth loss is associated with cognitive decline and incident dementia.Materials and MethodsWe analysed data from the Finnish population‐based Health 2000 and follow‐up Health 2011 surveys (participants aged ≥30 years and without dementia at baseline; N = 5506 at baseline and 3426 at 11‐year follow‐up). Dementia diagnoses until 2015 were ascertained from national registers (N = 5542). Tooth count was dichotomized as adequate (≥20) versus tooth loss (<20). Tooth loss was further stratified into 10–19 teeth, 1–9 teeth and edentulism. Upper and lower jaws were also considered separately. Baseline cognitive test scores were dichotomized by median as high versus low, and 11‐year change as decline versus no decline.ResultsTooth loss (<20) was associated with lower baseline overall cognition (odds ratio [OR] = 1.21, 95% confidence interval [CI] = 1.03–1.43), 11‐year cognitive decline (OR = 1.30, 95% CI = 1.05–1.70) and higher 15‐year dementia risk (hazard ratio = 1.52, 95% CI = 1.15–2.02) after adjusting for multiple confounders. After adjustment for dentures, associations became non‐significant, except for 10–19 teeth remaining and dementia. Results were similar after considering reverse causality bias; however, 10–19 teeth remaining was significantly associated with 11‐year cognitive decline even after adjustment for dentures. No jaw‐specific differences were observed.ConclusionsTooth loss adversely impacts the risk of cognitive decline and dementia. The role of dentures should be further explored.