Objective Night shift work has been linked to a higher incidence of some chronic diseases such as gastrointestinal or cardiovascular diseases. This is the first study assessing the prevalence of selected diseases and symptoms among middle-aged Polish night shift workers.

Methods We conducted a cross-sectional study of 605 blue collar workers in plants operating based on a shift system in Łódź, Poland. The study included 434 night shifts workers and 171 day-only workers (369 men and 236 women), aged 35–65. The employees coming to a periodic health examination to occupational physicians were invited to participate in the study. The data were collected via a self-administered questionnaire based on the “Standard Shiftwork Index”. Crude frequencies of occurrence of particular diseases and symptoms were calculated.

Results The mean age of the night shift workers and the day workers were similar, i.e. 47.6 and 46.6 years, respectively (p = 0.13). Hypertension (14.7%), high cholesterol/hypercholesterolemia (10.9%) and chronic back pain (10.9%) were the most common diseases in this population. The prevalence of hypertension (14.3% among the night shift workers) and gastric ulcer (6.0%) was slightly higher than in the general population in Poland in a similar age group (hypertension ~ 12% and gastric ulcer ~ 4%). The prevalence of irritable bowel syndrome (IBS) (1.2% among the night shift workers), coronary heart disease (CHD) (1.2%) and high cholesterol (9.9%) were slightly lower among the industrial workers compared to the general population in Poland (IBS ~ 13%, CHD ~ 5% and high cholesterol ~ 60%).

Conclusions Our study suggest some associations among Polish workers for the diseases potentially linked to night shift work, however further analyses are necessary (with adjustment for important confounders) to confirm these preliminary findings.