Disparities in utilisation of combined oral contraceptives in Aotearoa New Zealand: A cross-sectional whole-of-population study.

Abstract

The combined oral contraceptive (COC) is the most commonly used hormonal contraceptive in Aotearoa New Zealand (Aotearoa/NZ). Currently there is limited data available on who uses COC in Aotearoa/NZ. The aims were to (i) define the population of reproductive-aged females in Aotearoa/NZ in 2018 and identify the rate of COC use among this group and (ii) describe the sociodemographic and geographic characteristics of the population of COC users compared to the general population of reproductive-aged females in 2018. This whole-of-population cross-sectional study used the Integrated Data Infrastructure, a large research database managed by Statistics New Zealand. Females aged 16-50 years with complete sociodemographic and geographic information in 2018 from Aotearoa/NZ's estimated resident population were included. COC dispensing records to this cohort were identified from the national Pharmaceutical Collection. This paper reports descriptive counts of COC use and employs generalised linear regression with a binomial distribution and a log link to estimate adjusted risk ratios (aRR) of COC use for key sociodemographic and geographic subgroups. Of 1 113 750 individuals in the study, 159 789 (14.3%) were dispensed as COC in 2018. European/other individuals were most likely to use COC (aRR: 2.72, 2.67-2.78), and Pacific Peoples were least likely (aRR: 0.56, 0.55-0.58) to use COC. Individuals residing in the most deprived quintile had less COC use than individuals in the least deprived quintile (aRR: 0.73, 0.72-0.74). Our study is able to highlight significant disparities in use by ethnicity, area-level deprivation, and geographic factors.