A study followed 191 women from middle age to assess the relationship between cardiovascular fitness and later risk of dementia. The women were divided into high, moderate, and low fitness groups based on exercise tests in middle age. Over 44 years of follow up, those in the high fitness group had the lowest rates of developing dementia, at 5%, compared to 25% for the moderate group and 32% for the low fitness group. Being highly fit in middle age was linked to an 88% lower likelihood of developing dementia later in life. While the study does not prove fitness prevents dementia, it adds to evidence connecting cardiovascular health to brain health.