Trends in Vitamin D supplement use in a general female and Breast cancer population in Ireland: A repeated cross-sectional study

Abstract

Background Vitamin D has been linked with improved survival after Breast cancer diagnosis but little is known about prescribing rates. This study investigates trends in Vitamin D supplement use in both a general female and Breast cancer population. Methods Women with a Breast cancer diagnosis were identified from the National Cancer Registry of Ireland (n = 19870). Women who had any Vitamin D claim between 2005 and 2011 were identified from pharmacy claims data (n = 8556). Prevalence rates were calculated as a proportion of all eligible women and by age (< 55 years, 55 years). Poisson regression was used to compare rates of Vitamin D prescribing across years (risk ratio (RR), 95% CI). Results There was a statistically significant increase in women with a claim for Vitamin D between 2005–2011, with the largest increase among Breast cancer patients aged 55 years (RR = 2.26; 95% CI, 2.11–2.42). Conclusion This May have significant public health implications if associations between Vitamin D and improved Breast cancer survival prove to be causal.