Socioeconomic position, psychiatric medical treatment and risk of breast cancer recurrence and mortality: A Danish population-based cohort study

Background: Breast cancer patients with low socioeconomic position (SEP) have a higher risk of recurrence and mortality. We examined the extent to which prior psychiatric medication impacted this association.

Methods: We conducted a cohort study of premenopausal women diagnosed with breast cancer in Denmark from 2002 to 2011 (n = 5847), linking data from Denmark's nationwide population-based health registries on breast cancer diagnosis, treatment, psychiatric medication prescriptions and SEP indicators (marital status, cohabitation, income, education and employment). We followed the women up to 10 years from breast cancer diagnosis until recurrence, death, emigration, other malignancy, or September 2017. We used Cox regression to estimate hazard ratios (HRs) and corresponding 95 % confidence intervals (95 %CI) associating each SEP indicator with recurrence and all-cause mortality. To evaluate interaction by psychiatric medication use on the association between SEP and prognosis, we 1) stratified the models according to prior use of psychiatric medication and 2) added an interaction term to the regression model.

Results: Women with short compared with intermediate education level and prior psychiatric medication had increased risk of recurrence (HR = 1.41, 95 %CI = 1.05-1.91); this was higher than seen in those without prior psychiatric medication (HR = 1.06, 95 %CI = 0.87-1.29). Patterns were similar for all-cause mortality. Likewise, unemployed women with a history of psychiatric medication use had a higher risk of all-cause mortality (HR = 1.74, 95 %CI = 1.31-2.31) compared to unemployed women without prior psychiatric medication use (HR = 1.32, 95 %CI = 1.03-1.70). In contrast, prior psychiatric medication use did not have a negative impact on breast cancer prognosis in women who were single, living alone or had low income.

Conclusion: Breast cancer patients with prior psychiatric disease who have short education or are unemployed may be particularly vulnerable to recurrence and mortality. These women may benefit from more frequent follow up examinations.