Results of a 44-year-long study suggest that cardiovascular fitness in middle age lowers women’s risk of developing dementia later in life. These findings are the most recent in a growing line of studies that support a strong link between fitness and cognitive health throughout one’s lifespan.
The study, first published last week in Neurology, aimed at investigating the relationship between fitness and dementia risk in an attempt to control for factors that the authors say have limited previous studies of the same kind.
From a sample of 1,462 women from the Swedish population, 191 middle-aged subjects were recruited to participate in a study that would last over four decades, led by researchers out of the University of Gothenburg in Sweden. At the onset of the study in 1968, ages of the participants ranged from 38 to 60. Long-term prospective studies of this sort rarely span more than 20 years, and most involve participants who are over 60 years-old at baseline.
The study began with a fitness test in in which subjects completed a “stepwise-increased cycle ergometer test until exhaustion”, as a measure of cardiovascular fitness. Based on their performance during this test, women who participated were assigned to groups of high, medium, and low fitness, as well as a group of those who were unable to finish the test. This protocol was yet another defining characteristic of this study, as according to its authors, previous studies of the relationship between fitness and cognitive decline have relied solely on participants’ self-report of their physical activity level.
After the initial fitness test in 1968, follow ups were conducted on participants over the course of 44 years, on six separate occasions from 1974 to 2009, in order to test for incidence of dementia. Upon completion of the study, 45% of those women who were unable to finish the initial fitness test were diagnosed with dementia. 32% of those in the low fitness group, and 25% of those in the medium fitness group also received diagnoses of dementia. Of all the women in the high fitness group, only 5% developed dementia over the course of 44 years. Dementia was diagnosed in these women in accordance with DSM-III-R criteria.
These results showed that women with high cardiovascular fitness in their middle age were 88% less likely to develop dementia than those with medium fitness. In addition, for those in the high fitness group who did develop dementia, onset of dementia was on average 9.5 years later in life than those in the medium fitness group.
Helena Hörder, a lead author of the study, said in a recent statement: “These findings are exciting because it’s possible that improving people’s cardiovascular fitness in middle age could delay or even prevent them from developing dementia.”
However, an article from Forbes yesterday highlights some important limitations of the study, despite its several strengths, namely the fact that the women who participated underwent only one fitness test in their middle age as part of the study. For those who had either a good or bad day on the initial testing date, the test may not have been truly indicative of their cardiovascular fitness level.
In addition, because all women who participated were from Sweden, findings from this study may not apply to other populations of the world – although the researchers did try to control for confounding factors, like socioeconomic status, in analyzing the results.
The authors of the study also emphasize that the results only demonstrate an association between cardiovascular fitness in middle age and reduced dementia risk, not a causal relationship between the two.
Nevertheless, there is cause for optimism, as the results of this particular study largely support what has been called an “emerging theme” in the scientific literature: “staying physically fit strongly correlates with improved brain health.”