HRT 'cuts Alzheimer's disease risk'
14th February 2013 - Scientists have found that the process of cell ageing may be accelerated in menopausal women with an Alzheimer's risk gene, but that hormone replacement therapy (HRT) may be able to slow the process.
Researchers at Stanford University in California set out to study the effects of APOE4 - a gene which is known to raise the risk of developing Alzheimer's disease - and HRT on telomeres. These telomeres are short strips of DNA that are found in every cell which protect chromosomes as we get older.
Experts say they act like the little plastic caps on the end of shoelaces - stabilising chromosomes, keeping them from unravelling and preventing other damage.
However telomeres get shorter as we grow older and scientists can therefore use their length as an indicator of our biological age.
Two year study
The team followed 63 healthy post-menopausal women who had been using HRT for at least a year at the start of the study. 24 of the women carried the APOE4 gene. During the two year study, 31 of the women were selected at random to stop using HRT, while the remaining 32 stayed on HRT for the remainder of the study period.
Blood samples were taken at the start of the study and again two years later, while the rate at which telomeres shortened over the two year period was measured.
The scientists found that women who carried the APOE4 gene experienced a faster rate of telomere shortening than those who did not - suggesting that they were experiencing a faster rate of biological ageing. However, there was a slower rate of telomere shortening among those women who continued with HRT therapy for the whole two year period.
However, in women without this gene, the researchers found no link between the use of HRT and telomere length.
"This shows that APOE4 is contributing to ageing at the cellular level well before any outward symptoms of decline become apparent," says lead author Dr Natalie Rasgon, professor of psychiatry and behavioural sciences at the Stanford University School of Medicine. She continues in a statement: "Yet, oestrogen appears to have a protective effect for middle-aged women who are carrying this genetic risk factor."
Dr Simon Ridley, head of research at Alzheimer’s Research UK, comments in a statement: "Although this small study did not investigate whether HRT could prevent Alzheimer’s or measure its effects on cognition, the results could provide a useful new lead for research in this complex area.
"Currently there is mixed evidence surrounding the effects of HRT on Alzheimer’s risk, and some research suggests the timing of HRT may be important. Ultimately, we’d need to see large-scale, long-term trials to know whether HRT can prevent Alzheimer’s, and how the effects of this therapy might differ depending on our genetic make-up.
"We still need to know much more about the APOE4 risk gene, and this study has suggested important new clues about its possible effects. While it’s not clear how the process of cell ageing might be linked to Alzheimer’s, these results could eventually help scientists better understand the causes of the disease."