Hormonal replacement therapy in postmenopausal women is not associated with the incidence of cataract surgery: Evidence from 43 116 females in a Finnish nested case–control study

Today, cataract remains an important cause of treatable blindness globally. The prevalence of cataract is higher in women than in men, and exogenous hormone replacement therapy (HRT) for perimenopausal symptoms has been hypothesized to be linked with the gender difference in cataract development. Despite decades of research, literature remains still inconsistent and controversial (Defay et al., 2003; Kanthan et al., 2010; Zhang et al., 2021, 2023). In our study, we investigated the relationships between exogenous oestrogen only, progesterone only and combinatory oestrogen/progesterone HRT types and the incidence of cataract surgery in postmenopausal women over 50 years using data from the CARING study originating from a population of 398 708 individuals (Niskanen et al., 2020). We constructed a nested case–control design (NCC) with cases over 50 years of age on the CS event recorded between 1 January 2015 and 31 December 2017. Finally, our NCC study population consisted of 7186 female cases undergoing CS on any eye and 35 930 controls who did not undergo CS (five for each case). Controls were matched by year of birth with a calibre of 1 year and in the NCC, incident density sampling was used. Exogenous menopausal HRT exposure was estimated based on redeemed prescriptions in the past 20 years before the cataract surgery date. HRT exposure was assumed if at least two prescriptions per year were redeemed defined as (A) number of years with HRT (0–20) or (B) indicator for any HRT exposure in the last 20 years (no/yes). The potential confounding variables included diabetes mellitus (DM) (no/yes), socio-economic group and hospital district. NCC was modelled with conditional logistic regression that takes matching into account. Based on our findings, exogenous menopausal HRT was not associated with the incidence of cataract surgery in the Finnish population-based cohort (unadjusted or adjusted by DM, socio-economic group or hospital district; odds ratio (OR) with 95% confidence intervals NS in all) (Table 1). Our study confirmed the findings of no association with HRT and incident cataract surgery (Kanthan et al., 2010). Of note, the strengths of our study included a nested case–control design, knowledge of 20-year exposure to specific types of available HRT options, including a 3-year follow-up of a population with 43 116 female participants. Although exogenous menopausal HRT is known to increase the risks of some significant conditions, we found no associations with the incidence of cataract surgery (Zhang et al., 2021).