Women with high serum levels of oestrogen are less likely to suffer from cognitive decline than those with lower levels, say researchers from the US.
Dr Kristine Yaffe (department of psychiatry, University of California, San Francisco) and colleagues measured cognitive performance and blood levels of non-protein-bound (free) and loosely bound (bioavailable) oestradiol in women aged 65 years or more and repeated the measurements six years later. They then compared the results (Lancet 2000;356:708).
They found that women with high levels of free and bioavailable oestradiol had less decline in mental status than those with levels in the medium or low range. This suggests that free or bioavailable oestradiol is important in relation to the function of the central nervous system, they say. In a commentary on the paper (ibid, p694), Dr Mary Tierney (geriatric research, University of Toronto, Canada) suggests that women with low levels of free and bioavailable oestradiol are the group most likely to benefit from the "cognitive-enhancing" effects of HRT. This benefit might be seen even with a low dose of oestrogen, she says.
Over the six-year period, 39 of the 425 women died but, of the remainder, 16 per cent of women with low free oestradiol levels had cognitive impairment compared with 5 per cent of those with high levels. The results for bioavailable oestradiol were 15 and 5 per cent, respectively. The authors also measured testosterone over the study period to see whether there was any link between levels of this hormone and cognitive function but no relationship was found.