Evidence from the Million Women Study has shown that women who have hypertension (high blood pressure) in their 50s or 60s are at increased risk of developing vascular dementia in their 70s or 80s. The study is published in Alzheimer’s and Dementia.
Previous studies have demonstrated an association between hypertension and dementia but the evidence has been inconsistent in relation to types of dementia. It has also been suggested that having hypertension during pregnancy is associated with a higher risk of dementia later in life but there have been few large studies where participants have been followed up over a long enough period of time to be able to definitively say that the increased risk of dementia is due to hypertension in pregnancy or other factors.
In this study, researchers analysed data from 1.3 million participants in the Million Women Study, 16% of whom reported being treated for hypertension at recruitment to the study. Their health records were then followed up over an average of 21 years to identify participants who developed dementia. During follow-up, 84,729 participants developed dementia; of whom 27,522 were diagnosed with Alzheimer’s disease and 14,346 were diagnosed with vascular dementia.
The association between hypertension during pregnancy and risk of dementia was also investigated. After excluding women who had not had children, there were 1.2 million participants in the analysis, 27% of whom reported hypertension in pregnancy.
Key findings:
- Midlife hypertension was associated with a 17% increased risk of dementia;
- This was driven mainly by the association between midlife hypertension and vascular dementia, where there was a 50% increased risk of dementia in those with midlife hypertension compared to those without hypertension;
- There was no association between midlife hypertension and Alzheimer’s disease;
- Hypertension during pregnancy was associated with a small increased risk of dementia, but this was mainly due to the strong association between midlife hypertension and dementia. When midlife hypertension was taken into account, there was a weak association with dementia for women who had only had hypertension during pregnancy and not in midlife (5% increased risk of dementia).
Sarah Floud, Co-Principal Investigator of the Million Women Study and Associate Professor at Oxford Population Health, said ‘Our results have shown that midlife hypertension is a strong risk factor for dementia, particularly for vascular dementia. However, hypertension during pregnancy does not appear to materially affect dementia risk.
Public health efforts to prevent high blood pressure during midlife could lead to a considerable reduction in the incidence of vascular dementia.’