Survey shows shift workers have higher risk for prostate cancer

Men working on rotating shifts at factories, hotels, railways and other workplaces with 24-hour operations have a higher risk of developing prostate cancer than

those who work in the daytime, according to a study by a Japanese government-supported research group on epidemiology.

These men are 3.5 times more likely to develop prostate cancer than those who work regular hours and are also 2.8 times more likely to die of cardiovascular diseases, including stroke, according to the research group sponsored by the Ministry of Health, Labor and Welfare.

Little research has been conducted in Japan to examine the health effects of irregular working schedules. This latest research on relations between rotating shifts and prostate cancer risk was the first of its kind in the world, the group said in a preliminary report on the study.

The misaligned body clock due to irregular working schedules seems to be the culprit. A rise in blood pressure and accumulated stress are also seen to cause cardiovascular diseases, according to the report.

Shift workers' risks of suffering from cardiovascular diseases would become higher if they have other risk factors -- 6.5 times higher for those with high blood pressure, 3.1 times for those who smoke, 3.6 times for those who drink and 6.1 times for obese men with a body mass index of more than 25.

A body clock creates the physiological rhythm like sleeping and body temperature. Researchers said that the internal clock is misaligned when humans are exposed to strong light during the middle of the night, increasing the risk of causing sleeping problems and breast cancers.

About 20 percent of business offices in Japan have employees working after 10 p.m., with half of them operating on rotating shifts, according to a survey conducted by the Ministry of Health,Labor and Welfare.

Researchers said offices with 24-hour operations should review their labor management systems, including providing prostate cancer checks and giving special consideration to workers who have higher risks of developing cardiovascular diseases.

Using 1988-1999 health data for 110,000 people nationwide, the survey analyzed 16,000 male workers aged 40 to 79 to check the risks of prostate cancer and 18,000 male workers aged 40 to 59 to examine the risks of cardiovascular diseases.