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.

Fig 1

Overall trends in rate of women in receipt of any vitamin D per 1000 women for (i) GMS eligible national population and (ii) GMS breast cancer patients for years 2005–2011 with stratification by age group. Relative risks (RR) along with confidence intervals (CI) are also presented comparing 2011 to 2005 where the referent group for each RR is the group specific level in 2005.