Cancer risk and prognosis in Norway: comparing women in their first marriage with women who have never married.

STUDY OBJECTIVE

The difference in risk of cancer between never married women and married women in their first marriage and whether survival from cancer was any different between the two groups were studied.

DESIGN

This was a population based, nested case-control study of cancer in Norwegian women diagnosed between 1966 and 1990, and followed up with regard to overall survival until the end of 1991.

SETTING

Norway.

PARTICIPANTS

These were Norwegian women born between 1935 and 1954. The case-control study included 12,237 married and 1466 unmarried cases, and 26,075 married and 2768 unmarried controls. In the survival analysis, 11,943 married and 1473 unmarried cases were included.

MAIN RESULTS

Unmarried women had an overall increased cancer risk (OR = 1.13, 95% CI 1.05, 1.21), which could be attributed to cancer of the ovaries, uterus, brain and haematological malignancies. For cervical and thyroid cancer, the risk was lower than for married women. In the survival analysis, unmarried cases had an overall 26% increased risk of dying (HR = 1.26, 95% CI 1.15, 1.39), after adjustment for age and stage at diagnosis. The increased death rate was seen for cancer of the cervix, lung, and thyroid.

CONCLUSIONS

Since most unmarried women were nulliparous, this might explain their increased risk of ovarian and uterine cancer. The increased risk of brain tumours and haematological malignancies may result from selection bias, since disease among unmarried women may cause a large proportion to remain unmarried. The lower survival in unmarried cases may support the hypothesis that psychosocial factors play a role in the prognosis of cancer patients.