MedWire News: Women who work shifts are more likely to retire early due to poor health than those who work standard hours, results of a Danish study show.

Previous research has shown that shift workers are at increased risk of peptic ulcers, heart disease and other potentially debilitating conditions, explain Dr F Tüchsen, from the National Research Centre for the Working Environment in Copenhagen, and colleagues.

But they add that it is not known whether the risk of disability differs between male and female shift workers.

To investigate, the researchers studied data on 3980 women and 4025 men who participated in an occupational health study that began in 1990.

All the participants completed questionnaires about their working lives, health and lifestyles, and were monitored until they died, reached the age of 60 years or until the end of the study in 2006, whichever came first.

In total, 253 of the women and 173 of the men retired early on a disability pension because of poor health.

After accounting for factors such as smoking habits and workplace environment, the team found that female shift workers were 34% more likely to retire early on a disability pension than women who did not work shifts.

In contrast, male shift workers were no more likely to retire early due to poor health than other employees.

"Shift work is suspected to cause heart disease, breast cancer, peptic ulcer, sleep disturbances, compromised pregnancy outcome and accidents," write the researchers in the journal Occupational and Environmental Medicine. "It is therefore not surprising if the incidence of disability retirement is higher among shift workers."

But they add: "We have no knowledge about why women should be more vulnerable to shift work than men as our results suggest."

Dr Tüchsen and team therefore conclude that further studies are needed to investigate why shift work increases the risk of disability in women only.