Cognitive reserve (CR) can prevent the risk of incident cognitive impairment in the elderly. However, the moderator effects of CR on the link between hearing difficulties (HDs) and the risk of incident cognitive impairment are not well understood.

This cohort study obtained data from the Chinese Longitudinal Healthy Longevity Survey from 2008 to 2014. The baseline samples included 6309 participants aged 65 years and older at baseline. Cognitive impairment was assessed using the Chinese version of the Mini Mental State Examination. A composite measure of CR was calculated based on education, occupational complexity, and leisure activities of the participants. The marginal structural model was utilized to investigate whether CR moderates the association between HD and incident cognitive impairment. Odds ratios (ORs) and accompanying 95% confidence intervals (CIs) were calculated.

Of the 6309 participants at baseline, 1936 (30.7%) developed cognitive impairment during the 6-year follow-up period and 2562 (40.6%) reported HD. The risk of incident cognitive impairment was 1.90-fold (95% CI 1.69–2.14) for participants developing HD compared to those without. Those with middle CR had lower OR (0.72, 95% CI 0.62–0.82) that further decreased to 0.58 (95% CI 0.49–0.69) for those with high CR. Participants with HD with low CR showed the highest OR (4.32, 95% CI 3.42–5.47). In addition, individuals with HD with low education levels or low complex occupations had the highest risk of incident cognitive impairment.

CR moderates the negative association between HD and cognitive function. Education and occupation complexity may be more sensitive proxies for CR.