Rotating shift work, with night shift work, affects cardiovascular risk factors: a 6-year follow-up study in the insulation industry.

Objectives: To assess absolute levels and longitudinal changes in cardiovascular disease (CVD) risk factors over 6 years among rotating shift workers with night shift work and day workers in industry.

Methods: We studied three groups, 32 night shift workers in Plant A with a high night load, 23 in Plant B with a low night load and 25 day workers during a 6-year follow-up (FU). We collected demographics by questionnaire, measured blood pressure, resting heart rate, carotid intima-media thickness (cIMT), carotid to femoral pulse wave velocity (cfPWV) and maximal oxygen uptake (V̇O_2max). We analysed blood samples including lipids, glycosylated haemoglobin (HbA1c) and C reactive protein (CRP). Mixed models were used to assess changes and differences in changes of these outcomes between shift and day workers.

Results: Over the 6-year FU weight, cfPWV and CRP increased among shift workers with a high night load, and cIMT increased among shift workers with a low night load and among day workers. Over the 6-year FU, a significant decrease in V̇O_2max and an increase in HbA1c were found among all workers. The decrease in V̇O_2max and increase in HbA1c were associated with number of years in shift work.

Conclusions: Rotating shift work with night shift work in industry associates with weight increase, inflammation, arterial stiffness, increase in cIMT and HbA1c but also decreased V̇O_2max. Reducing the number of night shifts and including periods of restitution in the shift plan seem to mitigate some of the CVD risk factors.