Author response: Midlife cardiovascular fitness and dementia: A 44-year longitudinal population study in women

We are grateful for the comments by Kivimaki et al. on our article.1 We agree that the effect of dementia prevention in our study is probably overoptimistic. However, the results still suggest that there is a strong effect of midlife cardiovascular fitness on dementia risk in old age. Kivimaki et al. conclude that results based on 2 individuals with dementia are entirely based on chance. However, 44 individuals developed dementia during the 44-year follow-up period. Two of those were in the highest quintile of fitness. The low number of dementia cases in the highest-fitness group is thus the consequence of the strong effect of high midlife fitness on dementia risk. However, as Kivimaki et al. point out, this makes the exact estimation of the benefit of fitness less robust, but it still suggests a strong effect. Kivimaki et al. report that with 2 more cases, the population attributable fraction would decrease from 78% to approximately 60%. We would argue that this is also a strong effect. In addition, high fitness could be regarded as a sum of a number of beneficial factors related to dementia risk (e.g., genetics, exercise, diet, nonsmoking, and blood pressure).