Impact of exercising alone and exercising with others on the risk of cognitive impairment among older Japanese adults

•Older adults are more likely to exercise alone than with others.•Exercising alone for ≥ 2x/wk decreases the risk of cognitive impairment.•Exercising with others for ≥ 2x/wk decreases the risk of cognitive impairment.•If everyone exercises alone for ≥ 2x/wk, 15.1% of the incidence can decrease.•If everyone exercises with others for ≥ 2x/wk, 29.2% of the incidence can decrease.