Investigating the causal effect of cognition on the self-reported loss of functional dentition using marginal structural models: The Panel on Health and Ageing of Singaporean Elderly study

Aim: To assess the effect of cognition on the loss of functional dentition. Materials and Methods: We used data from the three waves of the Panel on Health and Ageing of Singaporean Elderly study (n = 4990 at baseline, 774 complete cases analysed) over 6 years (2009–2015). The outcome was the loss of functional dentition (<21 teeth). The exposure was cognitive impairment, while baseline confounders included age, sex, education, and ethnicity. Time-varying confounders included income, living arrangements, smoking, diabetes, depressive symptoms, cardiovascular disease, and body mass index. We used marginal structural mean models with inverse probability treatment weighted. Results: The mean age of the participants was 70.2 years at baseline. The proportion of participants with loss of functional dentition increased from 74.6% to 89.9% over 6 years. Women, ethnic Chinese, less educated, smokers, people with diabetes, and individuals with depression had a higher proportion of loss of functional dentition than their counterparts. Loss of functional dentition was 1.8 times higher (odds ratio 1.80; 95% confidence interval 0.88–3.69) among those with cognitive impairment after taking well-known confounders into account. Conclusions: After accounting for the time-varying exposure and confounding evidence, the association between cognition and functional dentition among the elderly in Singapore remains uncertain.