In our A2 Complete Companion we reported a study by Knutsson et al. (1986) who found that shift workers were three times more likely to develop heart disease than non-shift workers. A study just published by Hackam et al. (2012) confirms this, claiming a 24% increased risk of a coronary event and 5% increased risk of stroke. The study controlled for socioeconomic status, diet and general health of the workers.
It may be that problems arise because of poor day time sleeping and disruption to eating patterns and social routines. This might be improved by ensuring that shift workers have a minimum of two full nights’ sleep between after a period of night shifts, and should do both day and night shifts for alternate periods. See here for more detail.