1. High blood pressure in midlife was associated with an increased risk of cognitive decline.
2. Elevated systolic blood pressure in midlife but not late-life is, in particular, associated with cognitive decline.
Evidence Rating Level: 2 (Good)
Study Rundown: Previous studies have suggested that high blood pressure, particularly in midlife (45-55 years of age), may be associated with dementia. This study sought to confirm this association through analysis of psychomotor speed, memory, and executive function in a cohort of patients over the span of 20 years. Though this study demonstrated that higher blood pressure is associated with worse neurologic outcomes and increased rate of dementia, clinical trials of the effect of antihypertensive medication and aggressive blood pressure management are indicated before it can be definitively said that this would improve the rate of cognitive decline in hypertensive patients.
Strengths of this study include the fact that multiple data points were collected for each subject, as well as the long median follow up period. Because the study examined change in cognition versus simply taking a single evaluation of performance, confounders such as culture, sex, and IQ were excluded from analysis. A key limitation is that those patients with the most profoundly impaired cognitive status, as well as those with the most severe hypertension, had increased morbidity and mortality. This, along with the fact that the severity of those two variables often correlated, meant that certain subjects were lost from further analysis resulting in relatively small effect sizes.
In-Depth [prospective cohort]: This prospective cohort study examined 13,476 patients between the ages of 45-64 years old recruited from Maryland, North Carolina, Minnesota, and Mississippi. Cognitive evaluation was performed via the Delayed Word Call Test, as well as the Digit Symbol Substitution Test. The Word Fluency Test was also used to evaluate executive function. The cohort’s baseline characteristics were evaluated with regards to age, sex, race, BMI, educational level, presence of diabetes mellitus or alcohol use. APOE4 genotype and previous stroke were also analyzed. Patients were examined five times, and followed for a median of 19.1 years. Blood pressure was measured twice and averaged at each visit, and categorized as normal (systolic <120, diastolic <80 mmHg), prehypertension (systolic 120-130, diastolic 80-89 mmHg), or hypertension (systolic >140, diastolic >90 mmHg or use of antihypertensive medication).
Hypertension was associated with a greater 20-year cognitive decline (by 0.056 z score points, 95% CI -0.100 to -0.012) versus pre-hypertensive or normotensive patients. Individuals that were hypertensive but on antihypertensive medications were found to have a 20 year cognitive decline between prehypertensive patients and hypertensive patients not on medication (z score -0.05 95% CI -0.003 to -0.097).A faster rate of cognitive decline was seen in Caucasian patients as compared to African-American participants. There was no statistically significant correlation between hypertension in late-life and cognitive performance.
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