High cardiorespiratory fitness linked to lower risk of dementia, say researchers in BJSM article

Particpants given stationary bike test 

At enrolment, a six-minute submaximal exercise test on a stationary bike was completed to estimate CRF, cognitive function was estimated using neuropsychological tests, and genetic predisposition for dementia was estimated using the polygenic risk score for Alzheimer’s disease.

During the follow-up period of up to 12 years, 553 people (0.9 per cent) received a diagnosis of dementia. Participants were divided into three equal-sized groups standardised by age and sex according to their CRF scores for the analysis which showed that people with high CRF had higher cognitive function and a lower risk of dementia.

Compared with people with low CRF, the incidence rate ratio (IRR) of all dementia was 0.6 for people with high CRF, and onset of dementia was delayed by 1.48 years. A high CRF also reduced all dementia risk by 35 per cent among people with a moderate/high polygenic risk score.

Our findings suggest that maintaining favourable CRF could be a strategy for the prevention of dementia, even among people with a high genetic predisposition for Alzheimer’s disease [Shuqi Wang et al]

Caveats 

As the study was observational in nature, cause and effect cannot be established, say   and the researchers acknowledge various imitations to their findings.

Further research on the relationship between CRF and brain health – especially in older adults –and on the mechanisms by which CRF modifies the relationship between genetic risk and dementia is needed, they say.

Most importantly, the number of dementia cases may have been underestimated because UK Biobank participants are generally healthier than the general population, plus individuals with certain health conditions were excluded from the exercise test making the population investigated ‘healthier’ still.

The reliance on registries to identify dementia cases might have led to a further underestimation. Also, the submaximal exercise test used is considered less accurate than maximal exercise testing which requires participants to exercise to exhaustion, and any association between CRF change and dementia risk could not be examined due to the lack of repeat CRF measurements.

Conclusions

Professor Weili Xu and the co-authors conclude: ‘Our study shows that higher CRF is associated with better cognitive function and decreased dementia risk. Moreover, high CRF may buffer the impact of genetic risk of all dementia by 35per cent.’

They note: ‘Our findings suggest that maintaining favourable CRF could be a strategy for the prevention of dementia, even among people with a high genetic predisposition for Alzheimer’s disease.’

Further research on the relationship between CRF and brain health – especially in older adults –and on the mechanisms by which CRF modifies the relationship between genetic risk and dementia is needed, the authors add.

Fact file

• cardiorespiratory fitness (CRF) is the capacity of the circulatory and respiratory systems to supply oxygen to muscles and declines increasingly with age as skeletal muscle is lost.
• CRF declines by around 3 per cent to 6 per cent per decade when people are in their 20s and 30s, but this accelerates to more than 20 per cent per decade by the time people reach their 70s.
• low CRF is a strong predictor of cardiovascular events such as strokes and heart attacks and mortality from all causes

To access the full version of the article – titledAssociation of cardiorespiratory fitness with dementia risk across different levels of genetic predisposition: a large community-based longitudinal study doi:10.1136//bjsports-2023-108048 – click