Overall, Rasgon's team found, women with the E4 gene were much more likely to have substantial shortening in their telomere length. On average, they showed a decades' worth of telomere shortening in just two years -- a sign of accelerated cell aging.
That was the average, at least. When the researchers looked at E4 carriers who'd remained on hormone therapy, they saw no significant telomere shortening.
In contrast, among women who did not carry the E4 gene, there was no evidence that hormone therapy had a protective effect against telomere shortening.
"This suggests that hormone therapy may be protective in carriers," Rasgon said. "But the key word is 'may.''"
And why would hormones have such an effect? Rasgon said this study cannot answer that. There is animal research suggesting that estrogen might directly influence telomere length -- or affect it indirectly by, for example, lowering chronic inflammation in the body.
But no one knows if any of that animal research translates to humans, Rasgon said.
Peter Davies, an Alzheimer's researcher not connected to the study, also urged caution in interpreting the results.
For one, they are based on small numbers of women, said Davies, who directs the Litwin Zucker Research Center for the Study of Alzheimer's Disease at the Feinstein Institute for Medical Research in Manhasset, N.Y.
He also noted that the researchers looked at averages: Not all E4 carriers on hormones seemed protected against telomere shortening. By the same token, carriers who were off of hormone therapy did not always show accelerated shortening.
Davies agreed that the findings raise questions for future studies. But for now, there's no practical use for women. One reason is that most people have no idea if they carry the E4 gene. Testing is only done in the research setting -- not the doctor's office.
The same is true of telomere length. "You can't go out and have y
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