BackgroundThe decision‐making of older adults and people with dementia is attracting more attention among healthcare professionals. While cognitive impairment has been examined as a factor related to decision‐making, it can also be assumed that involvement in decision‐making leads to the maintenance of cognitive function. This study examined the association of the decision‐making process with the onset of cognitive impairment.MethodsWe analyzed data from a 2‐year longitudinal panel survey of community‐dwelling care recipients aged ≥65 years in Japan. The sample included 406 participants who responded to both baseline and follow‐up surveys, were cognitively intact at baseline, and had no missing cognitive impairment data regarding onset at follow‐up. The status of decision‐making involvement was assessed using a single item and classified into four categories: ‘very involved,’ ‘less involved,’ ‘unclear about desired care,’ and ‘having no one to share the decision.’ResultsAmong the participants (women, 65.0%; ≥75 years old: 68.2%), the incidence of cognitive impairment during the follow‐up was 26.6%. Multivariable logistic regression showed that, compared with highly involved participants, those who lacked clarity about desired care were more likely to develop an onset of cognitive impairment (odds ratio: 5.49; 95% confidence interval: 1.63–18.54; P = 0.006).ConclusionEven among cognitively intact care recipients, those who are not able to formulate their desired care may be at risk of cognitive decline. Therefore, support for the decision‐making process, not limited to the final decision, is essential to improving the prognosis of community‐dwelling care recipients.