Lower risk of dementia in older adults with higher baseline blood pressure

Older adults with higher baseline systolic blood pressure (SBP) values ​​have a lower risk of dementia, and clearer U-shaped associations between SBP and risk of dementia have only been observed in those over the age of 75, according to a study in JAMA Internal Medicine.

Data on the association between high blood pressure in late life and the risk of dementia are limited. Although some studies have found an association with increased risk, most suggest that there is a neutral or reduced risk associated with higher blood pressure. A possible explanation from previous and limited data suggests that late in life there is a U-shaped relationship where both high and low blood pressure are associated with risk of dementia.

The aim of the current study was to investigate whether the relationship between SBP and risk of dementia is U-shaped and whether age and comorbidity play a role in this context.

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The results are based on an analysis of 7 prospective, observational, population-based cohort studies investigating dementia in the elderly. Inclusion criteria were the availability of BP measurements in participants without dementia and subsequent data on dementia. The studies were initiated from 1987 to 2006 in Europe and the United States, and data analysis was performed between November 7, 2019 and October 3, 2021.

The studies included a total of 17,286 participants (mean [SD] Baseline age, 74.5 [7.3] Years; 60.1% women), of whom 2799 (16.2%) had incident dementia. The median time (interquartile range) to diagnosis was 7.3 (5.2-11.0) years or 136,473 person-years.

SBP and risk of dementia approximated an inverse linear association, with the nadir of the U-shape occurring at a high level of BP, with an SBP of 185 mm Hg (95% CI, 161-230 mm Hg; P=0.001) with the associated with the lowest risk of dementia. The lowest risk point was 160 mm Hg (95% CI, 154-181 mm Hg; p<0.001) for mortality and 163 mm Hg (95% CI, 158-197 mm Hg; p<0.001) for the combination of dementia and Mortality.

Associations were more clearly U-shaped in those aged 75 to 95 years, with the lowest risk points at around 165 mm Hg (range 158 mm Hg [95% CI, 152-178 mm Hg; P <.001] up to 170 mmHg [95% CI, 160-260 mm Hg; P =.004]).

The lowest risk points for mortality increased with age from 134 mm Hg (95% CI, 102-149 mm Hg; P=0.03) in those 60 to 70 years of age to approximately 160 mm Hg in those aged ≥ 70 years (range , 155 mmHg [95% CI, 150-166 mm Hg; P <.001] up to 166 mmHg [95% CI, 154-260 mm Hg; P =.02]).

The combined dementia and mortality risk curves were similar to those for mortality, and the observed associations were less pronounced for diastolic blood pressure.

Significant interactions were found for SBP in relation to baseline antihypertensive drug use and mortality (Akaike information criterion [AIC], -5.1; P for interaction = 0.01) and combined dementia and mortality (AIC, -2.2; P for interaction = 0.04), but not for dementia (AIC, 1.4; P for interaction = 0.27).

The researchers noted that the studies were conducted in different time periods, countries, and involved different methods of reducing blood pressure, population burden of disease and life expectancy, and the results are based on observational data. In addition, antihypertensive medication may have been started after BP and covariates were assessed at baseline.

“The results of this study suggest that lower SBP in older people overall may indicate a higher risk of dementia, U-shaped associations only occur in older age groups, and these associations cannot be explained by lower mortality from lower SBP,” the researchers noted.


van Dalen JW, Brayne C, Crane PK, et al. Association of systolic blood pressure with risk of dementia and the role of age, U-shaped associations and mortality. JAMA Intern Med. Published online December 13, 2021. doi:10.1001/jamainternmed.2021.7009

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