Occupational Medicine 2009;59:521 doi:10.1093/occmed/kqp107 MONITOR

Shift work risk of stroke and metabolic syndrome Up to 20 % of employees in industrialized nations work in rotating shifts or during the night. Concern persists over the possible increased risk of ischaemic heart disease (IHD) among shift workers [1–4]. Many early studies re-ported null findings explicable in part by small sample sizes or cross-sectional or case–referent design [5]. Up to six prospective studies [6–11] have examined this as-sociation, and all but two [6,11] reported a possible pos-itive correlation between shift work and risk of IHD. Some reports involved relatively small study groups [7,9] and others failed to consider potential confounding factors [6,10]. A major difficulty is the strong selection effect of heart diseases. Long before any clinical diagnose