Postmenopausal hormone therapy and cognition in twins

Objective: Mild cognitive impairment may be caused by pathophysiological changes occurring decades prior to symptom development. It has been hypothesised that oestrogen can prevent such changes. We aimed to investigate the association between postmenopausal hormone therapy and cognition in Danish female twins and to examine differences in this association before and after publication of the findings from the Women's Health Initiative study in 2002. Study design: This study includes cognitive assessment of 4510 twins aged 50+ years. Information on hormone therapy was obtained through Danish health registries. The association between current hormone therapy use and cognition was analysed in twins aged 50+ using both cross-sectional, intrapair and longitudinal analysis, adjusting for age, education, social class, and unobserved familial confounding. Results: Cross-sectionally, systemic HT users aged 70+ had a significantly lower cognitive function than nonusers, whereas systemic HT users aged 50-69 did not differ from non-users before 2002. Longitudinal data in younger twins aged 50-69 showed a significantly lower cognitive function in systemic HT users after 2002 compared to non-users. Systemic HT users aged 70+ showed that the lower cognitive function was most explicit before 2002, whereas after 2002 the cognitive function was closer to non-users. Twins aged 50-69 who changed from systemic HT to local HT after 2002, or dropped it altogether, performed cognitively better. Conclusions: Our findings cautiously indicate a change in the association between cognition and hormone therapy use after 2002, which suggests an alteration in the hormone therapy user profile in the wake of the 2002 WHI publication.