Cardiorespiratory fitness linked to preservation of cognitive abilities in older age

Higher cardiorespiratory fitness in older age is linked to the preservation of several core aspects of cognitive ability that are vulnerable to age-related decline, finds research published online in the British Journal of Sports Medicine.

And this association holds true irrespective of key risk factors for cognitive decline: age and carriage of the high risk APOE4 gene, the findings show.

Cardiorespiratory fitness is a physiological measure of aerobic capacity that can be modified by regular aerobic exercise. Although it has been linked to reduced risk of age-related cognitive decline and dementia, it’s not clear which aspects of cognition it might influence.

The researchers therefore wanted to find out if cardiorespiratory fitness was associated with core cognitive performance domains in 648 cognitively healthy 65–80 year-olds (average age 69).

Cardiorespiratory fitness was defined as the highest oxygen consumption (VO₂ max) recorded during a graded treadmill running test, while cognitive ability was assessed from the results of a comprehensive battery of validated neuropsychological tests carried out over two days.

The tests included several each to measure five domains: processing speed; working memory; visuospatial processing; episodic memory; and executive function/attentional control, which includes planning and organizational skills.

Most participants were women (461; 71%) and they had accumulated an average of 16 years of education. Some 15% reported taking a beta-blocker, a drug used for the treatment of heart conditions.

Participants had an average VO₂ max of 21.68 ml/kg/min. A good VO₂ max for men is 30–40 ml/kg/min. The equivalent figure for women is 25–35 ml/kg/min.

Among the 640 participants who were genotyped, 174 (27%) were APOE4 carriers.

As expected, older age was associated with poorer performance across all five cognitive domains, after accounting for sex, years of education, and weight (BMI), while educational attainment was associated with better performance.

But a higher level of cardiorespiratory fitness was associated with better performance across all five cognitive domains assessed, irrespective of age and APOE4 gene carriage.

The association between cardiorespiratory fitness and cognitive performance was greater in women, those with fewer years of education, and those taking beta-blockers, in the domains of processing speed and executive function/attentional control.

This is an observational study, and as such, no firm conclusions about cause and effect can be drawn. The researchers also acknowledge that not all cognitive domains were assessed—language, for example—and participants were all relatively inactive, so restricting the range of fitness levels observed

But they write, “These findings demonstrate the breadth of cognitive benefits associated with higher [cardiorespiratory fitness], and highlight several key factors that might influence the relationship between fitness and neurocognitive health in older adulthood.”

In a bid to explain the associations found, the researchers suggest that aerobic fitness may improve cerebral blood flow, reduce oxidative stress, forge new synaptic connections, boost the growth of neurons, and enhance neurotransmitter systems, as well as changing the shape and structure of gray and white matter.

Psychosocial factors linked to cardiorespiratory fitness, such as boosting mood, lowering fatigue, and improving sleep might also affect cognitive abilities, they add.

They conclude, “These findings highlight [cardiorespiratory fitness] as an important health factor for preserving multidomain cognitive functioning in older adulthood. Understanding moderators of this relationship might help to inform the development of individualized exercise prescriptions that target [cardiorespiratory fitness] to optimize cognitive health in aging.”