On 12 November, Yuan Ma and colleagues published a study in the PLoS Medicine journal, showing that large variations in blood pressure over a period of years are associated with a higher long-term risk of developing dementia. High blood pressure, also known as hypertension, is known to be a major risk factor for developing dementia in later life. However, studying the relationship between hypertension and dementia is complicated by the interlinked roles of aging and vascular comorbidities such as stroke. To investigate the association between dementia and long-term blood pressure variation, researchers turned to the Rotterdam study, a prospective cohort study that was initiated in 1989. The research team studied 5,273 participants who were dementia-free in 1989, 1,059 of whom developed dementia during the median follow-up period of 14.6 years.
After adjusting for factors such as age, sex, genotype and history of cardiovascular disease, participants were divided into 5 quintiles according to variation in systolic blood pressure (SBP) measured over a period of 2-4 years. Those who were in the highest quintile for SBP variation had the highest risk of developing dementia, which was most pronounced for the highest lag period in measurement of SBP variation (Hazard Ratio of 3.13 for a lag period ≥15 yrs, 95% CI 2.05-4.77). A higher risk of dementia was observed with both rises and falls in blood pressure, suggesting that variationper se, rather than direction of blood pressure change, influences dementia risk. Further studies are now required to establish whether the observed association is causal and to assess the effect of reducing blood pressure variability on dementia.
