Social Support, Social Strain, Stressful Life Events and Mortality Among Postmenopausal Women With Breast Cancer.

Introduction: Social support, social strain and stressful life events could induce chronic stress, which affects prognosis and survival after breast cancer diagnosis. However, few studies have examined the impact of psychosocial factors on different competing mortality events.

Methods: We included 9154 postmenopausal women who were newly diagnosed with invasive breast cancer after enrollment in the Women's Health Initiative, as of March 6th, 2021. Psychosocial factors were collected and stratified into quartiles. Cause of death was verified through adjudicated medical record reviews. Associations between psychosocial factors and all-cause mortality, breast cancer mortality, and cardiovascular disease mortality were examined by competing risk models. Subsequent stratified analyses were performed by race.

Results: With a median follow-up time of 8.6 years, 3218 deaths were identified. Compared to participants with less social support, those who had higher social support had significantly lower all-cause mortality (Q4 vs. Q1, HR = 0.89, 95% CI: 0.81, 0.9). The highest quartile of social strain was associated with lower CVD mortality (Q4 vs. Q1: HR = 0.80, 95% CI: 0.65, 0.99). After stratification, a similar relationship was found in White women but not in Black women.

Conclusion: Our findings suggest that there was an association between high social support and reduced all-cause mortality regardless of cancer stages at diagnosis. Social support interventions after breast cancer diagnosis could have the potential to reduce overall mortality.