exercise helps mental health

​A recent large study confirmed the benefit of physical exercise on mental health (see exercise and psych health lancetpsych2018 in dropbox or doi.org/10.1016/ S2215-0366(18)30227-X).

Details:

-- 1,237,194 people aged 18 or older in the US, enrolled in the Centers for Disease Control and Prevention Behavioral Risk Factors Surveillance System survey, in 2011, 2013, and 2015

-- compared the number of days of "not good" self-reported mental health in those who exercise vs not

-- groups were balanced for age, race, gender, marital status, income, education level, BMI, self-reported physical health, and previous diagnosis of depression

-- they assessed exercise type, duration, frequency, and intensity, adjusting for potential confounders as above

Results:

-- those who exercised had 1.49 (43.2%) fewer days of poor mental health the past month, after matching for physical and sociodemographic variables.

-- All exercise types were associated with lower mental health burden (11.8%-22.3%), p <2.2x10^-16 (!!)

-- The largest associations were for ;

    -- popular team sports (22.3% lower) [these are the usual team-type sports]

    -- cycling (21.6% lower)

    -- aerobic and gym activities (20.1% lower)

    -- and optimal  exercise duration was 45 minutes and frequency of 3-5 times per week (there was a smaller reduction if >90 min, and >3 hours was associated with worse mental health [?an OCD group??].

-- vigorous exercise was somewhat better than moderate or light

-- those people with a prior diagnosis of depression had an even greater benefit: 3.75 days (34.5% lower burden), p <2.2x10^-16 , with a similar ranking of benefit by exercise type as with the non-depressed group

-- they also assessed the “mindful exercises” of yoga or tai chi in post-hoc analysis: 22.9% benefit, which was better than walking or engaging in any other exercise

-- just doing household chores had a 9.7% reduction in poor mental health days (0.4 days/ month)

Commentary:

-- it is a bit misleading that they refer to the effects of exercise on "mental health", when they really mean depression or stress. Their assessment of mental health burden was the self-report on: “now thinking about your mental health, which includes stress, depression, and problems with emotions, for how many days during the past 30 days was your mental health not good?”

    -- However, depression is certainly one of the most common things we see in primary care. And has made it as the leading cause of disability around the world (globalization, anyone??). that being said, it is certainly much less likely that some other psych diagnoses are as amenable to exercise therapy (schizophrenia, schizoaffective disorder, substance use disorders, etc)

-- interesting how well the popular team sports did. Suggests that there may be an added value to the increased social aspects of this type of exercise. The effect of popular sports on depressive symptoms was independent of an underlying depression diagnosis.

-- also, on posthoc analysis, the mindfulness exercises (yoga, taichi) did well, suggesting that introspection itself may be useful

-- as an aside, this is the first time I have ever seen p-values reported this way. And 10^-16 is getting pretty close to the inverse of Avagadro’s number…..

-- of course, this observational study does not imply causality, despite attempts to control for many of the likely culprit variables (there may well be unanticipated confounders. and surveys are not necessarily totally accurate). And it is reasonable to assume that those more prone to depression may be less likely to exercise (decreased motivation), suggesting that reverse causality may be a factor. But there are some data which suggest that the exercise itself may lead to decreased depressive days:

    --there are RCTs showing positive effects of exercise on mental health (including mild to moderate depression in older adults, and as an adjunct for nonremitted major depressive disorder)

    --also lots of large observational studies mostly finding exercise is associated with reduced overall mortality, stress reduction, decreased cardiovascular disease, obesity, stroke, cancer (ie, a confluence of positive effects)

    ​--and, depression is frequently associated with increased inflammatory markers (as is cardiovascular disease, diabetes, visceral obesity); one of the effects of exercise is a decrease in inflammatory markers. is this decrease mechanistically related to the benefits of exercise on depressive symptoms???? is it related to the effects of exercise on diabetes/obesity/cardiovascular disease (as an aside)???

-- also, as a perspective, the association between exercise and depressive days was larger than several other modifiable risk factors: education (17.8% lower mental health burden if graduate college vs high school), BMI (4% worse if higher BMI), household income (17% better if >$50K vs $15K)

-- it was also interesting that they found a sweet spot for the amount of exercise, at 45 minutes/day, 3-5 times/week. this not only contradicts "the more, the better" mantra, but also is a reasonable, more actionable amount to suggest to patients

So, I bring up the study not because it’s so surprising. My guess is the most of us either knew or assumed that exercise was an important part of mental health. i think this study just adds impetus/justification/oomph to our advocating exercise (and not just for depression/stress reduction). And in an amount and intensity which is more likely to be acceptible to all. to me, this type of reminder of the importance of exercise is sort of like the blog showing that smoking only one cigarette/day is associated with a large % of the overall cardiovascular events attributable to smoking 1 pack/day (see http://gmodestmedblogs.blogspot.com/2018/01/smoking-just-one-cigarette-one-too-many.html​ ). this all helps empower us to help empower patients….

geoff

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