Pregnancy history may be linked to dementia – Alzheimer's Society comment

Researchers at Seoul National University in South Korea found that women who give birth to five or more children may be more likely to develop Alzheimer’s disease than women who have fewer births.

The study also showed that women who have had an incomplete pregnancy, whether through miscarriage or abortion, are less likely to develop Alzheimer’s disease in the future than women who have never had an incomplete pregnancy.

“It’s possible that the modestly raised levels of estrogen in the first trimester of pregnancy are within the optimal range for protecting thinking skills,” said study author Ki Woong Kim MD PhD.  

The study combined data from two independent population-based studies in Korea and Greece, totalling 3,549 participants. Limitations of the study are that it didn't record the timing and cause of incomplete pregnancies, didn't take into account the effects of hormonal birth control use over time and didn't compare women who had multiple pregnancies and/or incomplete pregnancies with women who had no pregnancies throughout their lives.

It's also possible that incomplete pregnancies were underestimated, either because abortions were not reported or women miscarried without realising.

Dr Doug Brown, Chief Policy and Research Officer at Alzheimer’s Society, said:

'We know women are more at risk of developing dementia than men but we don’t yet know why – and as it’s the only one of the top ten killers we can’t treat or cure, research like this is vital to better understand what causes dementia and how we might be able to reduce that risk.

'These researchers suggest that changing oestrogen levels during pregnancy may protect against dementia, but it’s a very complex relationship and so far trials using hormone replacement therapy to tackle dementia have been inconclusive.  

'There are also limits in the way this data was collected, like not comparing people who’d been pregnant with people who hadn’t, making it tricky to fully understand how pregnancy and childbirth affect dementia risk.

'This research shouldn’t give women who’ve given birth several times any cause for concern; it does highlight interesting links between changing hormone levels and dementia risk, but there are still too many unanswered questions. With dementia the UK’s biggest killer, we’re investing in a broad range of research that will one day beat dementia.'