“…Several studies have, for example, shown that work environmental factors, mainly physical but also psychosocial factors (Burr et al, 2011;Christensen et al, 2005;Labriola et al, 2006;Lund et al, 2006;Nielsen et al, 2006;Voss et al, 2004), lifestyle Robroek et al, 2011), and pain (Saastamoinen et al, 2009) are associated with SA. Further, some recent twin studies of the associations between socio-demography, health-related factors, pain, and DP showed that the associations seem to be independent from familial effects or influenced by those to a minor degree (Pietikäinen et al, 2011;Ropponen et al, 2011aRopponen et al, , 2011bSamuelsson et al, 2012).…”