Women who work night and evening shifts have an increased mortality risk compared with people who work day shifts, according to a study published in the March issue of the Scandinavian Journal of Work, Environment and Health.

Researchers have found a significant association between night-shift work and cardiovascular diseases and diabetes. The risk of contracting Alzheimer's and being affected by dementia is also significantly higher for nurses who work evening and rotating shifts.

The Danish research project found no evidence of an increased risk in mortality from overall cancer.

The study was based on data from the Danish nurse cohort. A total of 18 015 nurses were included in the study that was carried out by epidemiologists from the Chicago School of Public Health, the University of Copenhagen and the Danish Cancer Society.

The Danish nurse cohort study was initiated in 1993 when 23 170 female members of the Danish Nurses' Organization aged over 44 years were invited to participate in this nationwide study.

In 2007, the International Agency for Research on Cancer (IARC) classified shift work involving circadian disruption as 'probably carcinogenic' to humans (group 2A).