“…A total of 22 studies published in 26 papers fulfilled the criteria for inclusion [20-45]. Eleven studies were prospective, either in a traditional follow-up design [24,25,29,31,32,37-39,42] or the effect of an intervention in the work place was followed [20,21,26,27,36,40], and two studies had a case-control design [23,43], whereas nine studies had a cross-sectional design [22,28,30,33-35,41,44,45]. However, in most of the prospective studies, cross-sectional data analyses are also presented.…”