Prevalence and risk factors for sleep difficulty in a national cohort of Danish women treated for primary breast cancer 7-9 years following surgery. (#179)
Aim: While there is growing evidence indicating that cancer patients are at heightened risk of sleep difficulty at the time of diagnosis and treatment, little is known about long-term risk. The present study investigated the prevalence of and risk factors for clinically significant sleep difficulty in a national cohort of Danish women treated for breast cancer 7-9 years ago.
Methods: Three months after surgery, a total of 3343 (68%) women completed the Pittsburgh Sleep Quality Index (PSQI) together with questionnaires assessing depressive symptoms, trait anxiety, physical activity, and health behaviours. At follow-up, 7-9 years post-surgery, 2494 women were disease free and deemed eligible. Of these, 2085 (84%) completed the PSQI at follow-up. Data on disease status, treatment, and comorbidity were obtained from the Danish Breast Cancer Cooperative Group and surgical departments. Sociodemographic information was obtained from Danish national longitudinal registries.
Results: Three months post-surgery, 56.8% of the women reported clinically significant sleep difficulty (PSQI>5). The prevalence at 7-9 years posttreatment remained high, being 51.9%. A multiple logistic regression revealed seven prospective (baseline) risk factors for long-term sleep difficulty. In order of strength, these were: higher initial PSQI score (OR=1.25, 95%CI[1.21-1.29], p<0.001), lower personal income (in US$10,000: OR=0.91, 95%CI[0.85-0.96], p=0.001), greater trait anxiety (OR=1.05, 95%CI[1.02-1.09], p=0.002), higher body mass index (OR=1.04, 95%CI[1.01-1.06], p=0.01), being pre-menopausal (OR=1.55, 95%CI[1.10-2.20], p=0.01), having no children (OR=1.49, 95%CI[1.04-2.14], p=0.03), and having at least one parent born in Denmark (OR=1.91, 95%CI[1.02-3.57], p=0.04).
Conclusions: These results indicate that the prevalence of clinically significant sleep difficulty remains high for a long period after treatment for breast cancer. The combination of psychological and socio-cultural risk factors present at the time of primary treatment suggest that early interventions targeting psychological wellbeing, particularly anxiety, and effects of social inequality may be relevant for preventing or reducing long-term sleep difficulty in these women.