Cancer incidence in parents who lost a child: a nationwide study in Denmark

BACKGROUND: It has been debated whether psychological stress causes cancer, but the scientific evidence remains contradictory. The objective of this study was to investigate whether the death of a child is related to cancer risk in bereaved parents.

METHODS: The authors undertook a follow-up study based on national registers. All 21,062 parents who lost a child from 1980 to 1996 were recruited for the exposed cohort together with 293,745 randomly selected, unexposed parents. Cox proportional hazards regression models were used to evaluate the relative risk of cancer incidence up to 18 years after the bereavement. The main outcomes of interest were all incident cancers, breast carcinoma, smoking-related malignancies (International Classification of Diseases [ICD] 7 codes 140, 141, 143-149, 150, 157, 160-162, 180, and 181), alcohol-related malignancies (ICD7 codes 141, 143-146, 148-150, 155, and 161), virus/immune-related malignancies (ICD7 codes 155, 171, 191, 200-202, and 204), lymphatic/hematopoietic malignancies (ICD7 codes 200-205), and hormone related malignancies (ICD7 codes 170, 172, 175, and 177).

RESULTS: The authors observed a slightly increased overall cancer risk in bereaved mothers (relative risk [RR], 1.18; 95% confidence interval [95%CI], 1.01-1.37; P = 0.028) at 7-18 years of follow-up. There was an increased risk for smoking-related malignancies (RR, 1.65; 95%CI, 1.05-2.59; P = 0.010) among bereaved mothers during the 7-18 years of follow-up. The authors observed no significantly increased relative risk of breast carcinoma, alcohol-related malignancies, virus/immune-related malignancies, or hormone-related malignancies.

CONCLUSIONS: The current data suggest that the death of a child was associated with a slightly increased overall cancer risk in mothers and that the increase may be related to stress-induced adverse life styles.