Postmenopausal estrogen-based hormone therapy for a period lasting longer than 10 years is associated with a decreased risk of Alzheimer’s disease, research suggests.
The analysis study, conducted by researchers at the University of Eastern Finland, examined the results of four long large-scale studies covering two decades. The largest study comprised of approximately 230,000 Finnish women.
Two in every three Alzheimer’s cases are in women, and the postmenopausal depletion of sex steroid hormones – estrogen and progesterone – is thought to play a role in this.
Both in vitro and animal studies have suggested that estrogen has neuroprotective effects, but human studies have thus far yielded inconsistent results.
The researchers concluded that long-term postmenopausal hormone therapy – over 10-11 years – ‘was associated with a lower risk’ of Alzheimer’s disease.
They also detected a ‘protective association’ between long-term hormone therapy use and global cognition and episodic memory.
However, these effects were not replicated in women who had used hormone therapy over a shorter period.
They found short-term hormone therapy in postmenopausal women aged over 65 was associated with an increased risk of Alzheimer’s disease.
‘The protective effect of hormone therapy may depend on its timing: it may have cognitive benefits if initiated at the time of menopause when neurons are still healthy and responsive,’ said lead author Dr Bushra Imtiaz.
‘In the light of these findings, hormonal replacement therapy may have a beneficial effect on cognition if started early, around the time of menopause.
‘The protective effect of hormonal therapy may depend on the health status of neurons at baseline and may be lost if therapy starts years after menopause.’
Further findings suggested that the postmenopausal removal of ovaries, uterus or both was not significantly linked to the risk of Alzheimer’s disease.