High blood pressure (BP) increases the risk of dementia; however, few studies have reported on the risk of dementia in patients with low-risk, early-grade hypertension. We investigated the protective effect of controlled BP on risk of dementia in treated, low-risk, grade 1 hypertensive patients from the entire National Health Insurance Service National Health Examinee cohort.
We selected grade 1 hypertension (140–159/90–99 mmHg) patients with low risk, diagnosed in 2005–2006. All patients (N = 128 665) were classified into controlled (average BP < 140/90 mmHg during the follow-up) and uncontrolled (average BP ≥ 140/90 mmHg) BP groups and followed up until 2015. The risk of dementia was estimated using Cox proportional hazard model after adjustments for propensity score.
Average BP was 131/81 mmHg in the controlled group (N = 49 408) and 144/87 mmHg in the uncontrolled group (N = 99 257). Overall dementia incidence rates in controlled and uncontrolled groups were 4.9 and 8.1 per 1000 person-year, respectively. The controlled group showed lower risk of overall dementia, Alzheimer's disease, and vascular dementia than the uncontrolled group. The controlled group had a low risk of vascular dementia at all ages, especially in the younger group (age <60). The optimal BP level associated with the lowest risk of dementia was 130 to less than 140 mmHg for SBP and 70 to less than 80 mmHg for DBP.
We concluded that among even low-risk and grade 1 hypertension patients, controlled BP significantly reduced the risk of dementia, including Alzheimer's disease and vascular dementia.