As little as 100 minutes per week of moderate-intensity physical activity, such as brisk walking, may be sufficient to significantly lower the risk of depressive symptoms and odds of major depression among older adults, according to new research published in JAMA Network Open.
The researchers conducted this study to address the pressing issue of depressive symptoms and disorders among older adults, which are highly prevalent and debilitating. These conditions not only affect the quality of life for older individuals but also pose significant risks for various chronic diseases, cognitive and functional decline, cardiovascular issues, chronic pain, all-cause mortality, and suicide. Additionally, depression places a substantial economic burden on healthcare systems, with an estimated cost of over $210.5 billion in the United States alone.
Previous research had shown some promise regarding the prophylactic effects of regular physical activity in preventing depression. However, there was a lack of consensus on the optimal amount of physical activity needed for protection against depression and whether this requirement varies among individuals with and without chronic diseases.
“Depression in older adults is a major health issue and is a major contributing factor to chronic disease, pain and suicide,” said study author Eamon J. Laird, a researcher at the Health Research Institute at the University of Limerick. “It also comes with a huge socio-economic burden increasing healthcare costs and decreasing quality of life. Previous work had shown that moderate to vigorous physical activity (MVPA) was linked with reduced risk of depression but we didn’t know what the lowest dose was where there might be benefits.”
The methodology of the study involved using data from The Irish Longitudinal Study on Ageing (TILDA), a population-representative study of older adults in the Republic of Ireland. The researchers collected data from 10 years of TILDA surveys (waves 1-5) spanning from October 2009 to December 2018. The study included adults aged 50 years and older from the Republic of Ireland, with a final analytical sample of 4,016 participants.
Depressive symptoms were measured using the short form of the Centre for Epidemiological Studies Depression (CES-D) score. Major depression status was classified based on CES-D scores and/or a diagnosis of a major depressive episode during the past 12 months.
Physical activity was assessed using the short-form International Physical Activity Questionnaire. Participants reported the number of days and duration of various physical activities (vigorous, moderate, and walking) over the previous 7 days, and this data was converted into Metabolic Equivalent of Task (MET) minutes per week.
MET is a unit used to represent the metabolic rate or the amount of energy your body uses while performing a specific activity. Activities that require more effort have higher MET values. For example, 600 MET minutes is the equivalent of 150 minutes of moderate intensity activity or about 75 minutes of vigorous intensity physical activity.
The researchers found that depression rates increased from a mean of 8.2% to 12.2% over the 10-year time period. Additionally, the use of prescribed antidepressant medications also increased during this time. Meanwhile, the proportion of participants meeting or exceeding physical activity guidelines (at least 600 MET-min/wk) decreased from 51.1% at the beginning of the study to 40.9%.
For both individuals with and without chronic disease, higher physical activity was associated with better mental health. This was true even for participants who didn’t meet the physical activity guidelines. Those performing 400 to 600 MET-min/wk had a 16% lower rate of depressive symptoms and 43% lower odds of major depression compared with participants performing 0 MET-min/wk.
“In our large study, across ten years of follow-up, our findings indicated that accumulating as little as 100min/week, or 20min/day for five days/week, of moderate-intensity activity (e.g., brisk walking; 4 METs) may be sufficient to significantly lower risk of depressive symptoms and odds of major depression over time among older adults,” Laird told PsyPost.
“Importantly, our findings support a dose-response relationship for MVPA with depression; as the dose increased the risk of depression reduced,”
There was an incremental decrease in depressive symptoms with each increase in physical activity dose, with 7%, 16%, and 23% lower rates of depressive symptoms among those meeting recommendations, exceeding recommendations, and with the highest doses, respectively. Similarly, 600 to less than 1200 MET-min/wk was associated with 44% lower odds of major depression, while 2400 MET-min/wk or more (the highest dose MVPA category) was associated with 49% lower odds of major depression.
“It was surprising that a lower dose than that recommended by WHO guidelines was still linked with lower risks of depression,” Laird said. “Older adults can often find it difficult to perform activity and it was reassuring to see even a small amount of MVPA could have real benefits for depression. However, it’s important to remember that we observed the higher the dose of the activity the greater the benefits for depression.”
The researchers controlled for various covariates such as age, sex, educational level, antidepressant use, chronic disease status, smoking, alcohol use, and body mass index. But the study, like all research, includes some caveats.
“MVPA and depressive symptoms, but not Major Depression from the CIDI-SF, were self-reported, risking over- or under-reporting and potential social desirability biases, and depression was not controlled for family history,” Laird explained. “Due to the nature of the data we used, we were unable to consider chronic pain, sleep information, or family history of depression which may influence the relationship. In addition, given the ethnic composition of our sample, our findings are only generalizable primarily to white/Caucasian older adults.”
“In future research, we would like to examine other population and ethnic groups and also use device-measured physical activity to corroborate self-reported activity. We would also like to complete a randomized controlled trial using our findings to show it can be replicated. Lastly, we would like to investigate the interactions with nutrition and sleep as physical activity is one component and we know little about interactions or cumulative effects in real world settings.”
The study, “Physical Activity Dose and Depression in a Cohort of Older Adults in The Irish Longitudinal Study on Ageing“, was authored by Eamon Laird, Charlotte Lund Rasmussen, Rose Anne Kenny, and Matthew P. Herring.
