exercise and cognitive health

exercise and cognitive health

G

Geoff A. Modest, M.D.

Wed 1/15/2020 7:38 AM

• Geoff A. Modest, M.D.

 

Another study came out finding that moderate-to-vigorous physical activity (MVPA) was associated with a larger brain hippocampus, the area of the brain involved in consolidating information from short-term memory into long-term memory, and also one of the 1^st regions in the brain found to be damaged in those with dementia, including Alzheimer's (see exercise and hippocampal volume brainimaging2019 in dropbox, or doi.org/10.1007/s11682-019-00148-x)

Details:

-- data is from the UK Biobank, the largest known inventory that includes neuroimaging data, objective measures of MVPA (via wearable accelerometers, worn for up to 7 days), and the data needed to estimate cardiorespiratory fitness (CRF). There were no exclusion criteria for this databank, though volunteers were required to attend an assessment center

-- 7148 individuals (the subset of the 500,000 adults in the databank that also included MRI scans of the brain), 57% female, median age 62, BMI 26, resting heart rate 70, college degree 46%, never smokers 51%, previous smokers 33%, doctor diagnosed CVD 25%, doctor diagnosed diabetes 5%

Results:

-- objectively measured MVPA was correlated with CRF, though this was not strong: MVPA explained only 5% of the variation of CRF

-- the fully adjusted models included age, sex, education, Townsend deprivation index (a continuous and objective measure of socioeconomic deprivation), smoking status, physician diagnosed cardiovascular disease (angina, MI, stroke, hypertension) and physician diagnosed diabetes (though removing those on beta-blockers given their effect on heart rate)

    -- adjusting for covariates including MVPA, CRF was positively associated with overall gray matter volume

    -- adjusting for CRF, MVPA was associated with increased left and right hippocampal volumes but not overall gray matter volume

    -- both CRF and MVPA were associated with decreases in white matter hyperintensity lesions (WMH), a quantification of lesions in the white matter that presumably signify vascular disease and are associated with increased risk of stroke, dementia and death

    -- all of these associations were highly statistically significant, though there was only a trend to an association between MVPA and white matter volume

-- neither sedentary behavior nor light physical activities showed significant associations with changes in brain

Commentary:

-- this article tried to dissociate the effects of MVPA and CRF, which is important because though long-term MVPA is associated with improved CRF, about 50% of the variation in CRF seems to be a heritable and not related to MVPA

-- older studies have found mixed results on the relative effects of CRF and MVPA, some finding that CRF was a better predictor of the volume of brain structures. Recent studies have found that white matter volume and WMH are improved with both CRF and MVPA, with the suggestion that MVPA is more consistently related.

-- this article follows a recent article in JAMA on exercise and brain volume based on data from the Framingham study. Though that study found that light intensity exercise improved MRI-measured total brain volume, higher levels of exercise significantly increased hippocampal volume (see http://gmodestmedblogs.blogspot.com/2019/04/light-intensity-exercise-improves-mri.html )

-- several other studies have found that aerobic exercise is associated with beneficial effects both in brain structure and cognitive function, especially in the elderly

-- physical activity has several potentially beneficial neurologic effects including increased blood flow to the brain, increased nutrients, and clearing molecules that may affect brain health and risk for disease. MVPA in particular is associated with increased cerebral blood flow and vascular health, and also upregulates the production of brain-derived neurotrophic factor (BDNF), which is associated with neurogenesis, neural protection, synaptic plasticity, learning, and memory (animal studies suggest that BDNF is associated specifically with neurogenesis in the hippocampus, as well as with maintenance of white matter)

-- the authors also feel that their results are consistent with their Adaptive Capacity Model, whereby the combination of aerobic physical activity and cognitive challenges experienced during exercise may have an even more important role in the preservation of brain structure during aging (see exercise cognition evolution trndsneurosci2017 in dropbox, or doi.org/10.1016/j.tins.2017.05.001). They suggest that from an evolutionary perspective humans evolved in the setting of exercise associated with constant cognitive pressures (surveying the savanna for predators as well as likely food sources, balancing on 2 legs while running on uneven terrain/complex environments at high speed). This theory is supported by animal studies showing that brain development (especially in the hippocampus) related to a combination of exercise plus cognitive challenge is superior to that of exercise alone, and this combo also leads to increased production of BDNF. Human studies have also found that combined exercise and cognitive training is superior to exercise alone, though some studies do suggest that these 2 tasks need not be undertaken simultaneously but there could be a few hours separation; longer delays do not seem to have the same benefit

    -- one consequence of this theory is that exercise in the setting of going to the gym and watching TV may be less beneficial than outdoor exercise, with its attendant array of sensory inputs and cognitive requirements. And, perhaps there would be benefit from indoor exercise plus associated cognitive tasks, such as solving puzzles at the same time, preferably using a validated intervention. Of note, I read the recent article in Scientific American on this theory while working out at the gym. Would that qualify as cognitive stimulation???? (see https://www.google.com/search?q=scientific+american+why+your+brain+needs+exercise&rlz=1C1CHBF_enUS748US748&oq=scientific+american+brain+needs+&aqs=chrome.2.0j69i57j0.18566j0j7&sourceid=chrome&ie=UTF-8 )

 -- by the way, there was a recent opinion piece in the NY Times written by a 62yo neuroscientist who basically argues that cognitive decline in the elderly is overstated, that younger people have memory lapses but in older people these are over-attributed to aging (see https://www.nytimes.com/2020/01/10/opinion/sunday/age-memory.html)

-- Limitations of study:

    -- they did not use the gold standard for measuring CRF, VO_{2 max}, but used a validated nonexercise estimate (a cycle ergometer while wearing a 4-lead EKG, with increasing resistance)

    -- MRI evaluates only quantitative measures of brain volume, and not the intricacies of the neuronal interconnections, so it is really only a surrogate measurement of brain function

    --and, this is a pretty large data-mining study from a large databank. So, it does not include important confounders that were not assessed (eg, medical comorbidities in detail, meds, depression, stress…..). For example, chronic stress and depression are well-known to deplete hippocampal size, as well as hippocampal neural connections. And these can improve with remission of depression or stress but only after several weeks (with the argument that it takes at least 4 weeks to see an effect of SSRI antidepressants, about the same time it takes for the hippocampus to renew). And exercise does help with depression and stress: see http://gmodestmedblogs.blogspot.com/2018/09/exercise-helps-mental-health.html

-- Other blogs of note related to lifestyle and cognitive health:

    -- overall, the Mediterranean diet was associated with the equivalent effects of 5 years of decreased aging on the brain architecture, especially those with higher fish and lower meat intake. See https://gmodestmedblogs.blogspot.com/2015/11/mediterranean-diet-and-brain-volume.html). For an array of blogs on the clinical benefits of Mediterranean diet, see http://gmodestmedblogs.blogspot.com/search/label/Mediterranean%20diet 

-- for the large array of blogs on the positive effects of physical activity, both physical as well as psychological, see https://gmodestmedblogs.blogspot.com/search/label/physical%20activity . Even short-term exercise interventions may prevent hippocampal atrophy in older adults and do improve brain connectivity

-- recent US health surveys have suggested that doing only 5 to 10 minutes of light-to-moderate leisure time physical activity a day had significant mortality benefits (see https://gmodestmedblogs.blogspot.com/2019/03/5-10-min-of-exercise-may-improve-health.html )

so, there does seem to be pretty strong evidence that moderate-to-vigorous exercise is effective in improving hippocampal size and function, and studies suggest that this is related to improved memory and executive function.  This finding, in addition to the studies showing that diet seems also to be beneficial, point to the real importance of a healthy lifestyle in cognitive health, as well as (per many prior blogs) on total mortality, heart disease, diabetes, hypertension, cancer, NAFLD, mental health .......

geoff​

If you would like to be on the regular email list for upcoming blogs, please contact me at gmodest@uphams.org

  

to get access to all of the blogs:

1. go to http://gmodestmedblogs.blogspot.com/ to see them in reverse chronological order

2. click on 3 parallel lines top left, if you want to see blogs by category, then click on "labels" and choose a category​

3. or you can just click on the magnifying glass on top right, then  type in a name in the search box and get all the blogs with that name in them

please feel free to circulate this to others. also, if you send me their emails, i can add them to the list