Do physical activity and body mass index modify the association between chronic musculoskeletal pain and insomnia? Longitudinal data from the HUNT study, Norway
Some evidence indicates that musculoskeletal pain may increase the risk of insomnia (Ødegård et al., 2013; Tang et al., 2015), although contrasting results have been reported (Leblanc et al., 2009). In a longitudinal cohort study, Ødegård et al. (2013) found that chronic musculoskeletal pain was associated positively with risk of insomnia at 10–11 years’ follow‐up in adult women and men who were free from insomnia at baseline. A recent study of older adults found that reporting of 1 day or more with musculoskeletal pain during the previous month was associated with increased risk of insomnia at 3‐year follow‐up (Tang et al., 2015).
Although the current evidence indicates an association between chronic musculoskeletal pain and risk of insomnia, the exact nature of this association remains unclear. It is conceivable that the impact of chronic musculoskeletal pain on risk of insomnia may interact with modifiable risk factors such as physical activity and obesity. Obesity and weight gain have been associated with increased risk of insomnia (Palm et al., 2015; Singareddy et al., 2012), while regular physical activity is considered important for promotion of good sleep (Chennaoui et al., 2015; Yang et al., 2012). Although chronic pain, obesity and physical activity may be closely intertwined, little is known about their joint effect on risk of insomnia.
In a population‐based prospective study, we investigated the association between chronic musculoskeletal pain and risk of insomnia defined by insomnia symptoms. We hypothesized that (i) risk of insomnia is associated positively and dose‐dependently with number of chronic musculoskeletal pain sites, and (ii) that excess body mass and low leisure‐time physical activity amplify the adverse effect of chronic musculoskeletal pain on risk of insomnia.