Sitting-time, physical activity, and depressive symptoms in mid-aged women
American Journal of Preventive Medicine, 09/20/2013
van Uffelen JGZ et al. – The study aims to examine concurrent and prospective associations between both sitting–time and physical activity with prevalent depressive symptoms in mid–aged Australian women. Increasing physical activity to a level commensurate with guidelines can alleviate current depression symptoms and prevent future symptoms in mid–aged women. Reducing sitting–time may ameliorate current symptoms.
Data were from 8950 women, aged 50–55 years in 2001, who completed mail surveys in 2001, 2004, 2007, and 2010.
Depressive symptoms were assessed using the Center for Epidemiological Studies Depression questionnaire.
Associations between sitting-time (≤4 hours/day, >4–7 hours/day, >7 hours/day) and physical activity (none, some, meeting guidelines) with depressive symptoms (symptoms/no symptoms) were examined in 2011 in concurrent and lagged mixed-effect logistic modeling.
Both main effects and interaction models were developed.
In main effects modeling, women who sat >7 hours/day (OR=1.47, 95% CI=1.29, 1.67) and women who did no physical activity (OR=1.99, 95% CI=1.75, 2.27) were more likely to have depressive symptoms than women who sat ≤4 hours/day and who met physical activity guidelines, respectively.
In interaction modeling, the likelihood of depressive symptoms in women who sat >7 hours/day and did no physical activity was triple that of women who sat ≤4 hours/day and met physical activity guidelines (OR 2.96, 95% CI=2.37, 3.69).
In prospective main effects and interaction modeling, sitting-time was not associated with depressive symptoms, but women who did no physical activity were more likely than those who met physical activity guidelines to have future depressive symptoms (OR=1.26, 95% CI=1.08, 1.47).
Jannique G.Z. van Uffelen (09/19/2013)
An interesting finding in our study was that sitting-time was associated with current depressive symptoms, but not with future symptoms. There are several potential explanations for this, which are described in more detail in the article. A particularly interesting explanation is the potential of reverse causality. Fatigue and loss of energy are common depressive symptoms and it could therefore be the case that, instead of high sitting-time causing depressive symptoms, depressive symptoms cause high sitting-time. Although this seems to be a logical explanation, we did not find evidence for reverse causation in our study.
For a 6 minute video cast of the paper, please see: http://www.scivee.tv/node/60419
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