Does pain mediate or moderate the relationship between physical activity and depressive symptoms in older people?

A recent study involving participants 50 years and older from Northern Ireland (NI) and the Republic of Ireland (RoI) (N=6159) found core depressive symptoms (i.e. depressed mood and anhedonia) in 7.2% of their nationally representative sample (Morgan, O’Farrell, Doyle and McGee, 2011). This study also showed that those who were engaged in moderate to high levels of physical activity (PA) had a 50-56% reduction in the odds of having elevated depressive symptoms compared to those with low levels of PA (Morgan et al., 2011). Unfortunately, the analyses omitted a potentially significant explanatory variable – pain. Pain has been shown to be associated with increased risk for depression in older persons (Bair, Robinson, Katon and Kroenke, 2003; Onder, Landi, Gambassi, et al., 2005), and is also a potential reason for nonengagement in PA (Mossey, Gallagher and Tirumalasetti, 2000). It could therefore interact with (mediate or moderate the association between) depression and PA. This report details a set of analyses that investigates this in three nationally representative datasets of older adults from both the RoI and NI.