Rotating night shifts increase nurse death risk by 11%, Harvard study finds

Long-term care nurses who work rotating night shifts might be at increased risk of death, particularly from heart disease and lung cancer, according to recently published findings from Harvard Medical School.

For nurses who worked rotating night shifts for at least six years, all-cause mortality increased 11%, the investigators determined. Cardiovascular disease mortality was about 20% higher for this group. For nurses who worked this type of schedule for 15 or more years, risk of death by lung cancer increased 25%.

Rotating night shifts were defined as at least three night shifts a month, interspersed with day and evening shifts. The researchers analyzed 22 years of data from about 75,000 nurses who took part in the Nurses' Health Study. The study began in 1976 and involves biennial questionnaires.

The findings do not prove that rotating night shifts cause heart disease, cancer or other conditions that lead to death, the authors emphasized. But prior research also has shown a correlation between night shifts and worse health outcomes and higher mortality, they noted. Theories suggest that night work might harmfully disrupt the body's circadian rhythms.

Future work might focus on how the “duration and intensity” of night shift work affects people, and whether different types of people display different responses over time, according to lead author Eva Schernhammer, M.D., Ph.D., of Harvard Medical School and Brigham and Women's Hospital.

Full findings appear in the American Journal of Preventive Medicine.