Blood pressure and dementia risk
Hypertension in midlife is related to approximately 60% increased dementia risk. However, this association is less prominent later in life, with few studies showing increased risk associations. On the contrary, some studies in late life find that hypertension is associated with decreased dementia risk. A possible explanation for these seemingly paradoxical results may be that with aging, U-shaped relationships between blood pressure (BP) and dementia risk develop, with both high and low BP signaling elevated dementia risk. Some relatively small studies have found such U-shaped associations. However, the extent to which these results are generalizable and how they are affected by aging, comorbidities, and limited life expectancy remains unclear. This study investigated whether the relationship between systolic blood pressure (SBP) and dementia risk is U-curved and whether age and comorbidity are involved.
Seven European population studies were used to explore this, including three NEAR studies: the Kungsholmen Project (KP), the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K), and the Gothenburg H70 Birth Cohort Study (H70).
Dementia risk is lower for older individuals with higher systolic blood pressure
In 17 286 participants with a mean age of 75 years, dementia risk was decreased for persons with higher SBP. Although there was no clear U-shape for dementia overall, the least dementia risk was estimated for individuals with an SBP of approximately 185 mm Hg. U-shaped dementia relationships were more prominent in individuals aged >75. As for mortality, the lowest risk was for individuals with an SBP of 160 mm Hg, indicating a clear U-shaped association. The U-shape for mortality was seen across all age groups, with the least dementia risk associated with 134 mm Hg in those aged 60 to 70 years old. Between 70 and 95 years of age, it increased to between 155 mm Hg and 166 mm Hg. Overall, this study found that dementia risk was generally lower in older adults with higher SBP levels, and U-shaped relationships were more common after 75 years of age. The results for mortality suggest that the association of low BP with elevated dementia risk cannot be explained by individuals with low BP having a longer life expectancy. This makes them more likely to develop dementia. To counteract dementia risk in older adults, future trials on BP management need to consider age and health.
van Dalen JW, Brayne C, Crane PK, Fratiglioni L, Larson EB, Lobo A, Lobo E, Marcum ZA, Moll van Charante EP, Qiu C, Riedel-Heller SG, Röhr S, Rydén L, Skoog I, van Gool WA, Richard E. Association of Systolic Blood Pressure With Dementia Risk and the Role of Age, U-Shaped Associations, and Mortality. JAMA Intern Med. 2022; 182(2): 142-152. doi.org/10.1001/jamainternmed.2021.7009.