Association between systolic blood pressure and dementia in the Whitehall II cohort study: role of age, duration, and threshold used to define hypertension
What are the associations of diastolic (DBP) and systolic blood pressure (SBP) at ages 50, 60, and 70 years with incidence of dementia, and does cardiovascular disease (CVD) over the follow-up mediate this association? Methods: Data from the Whitehall II cohort study were used for the present analysis. SBP and DBP were measured in 1985, 1991, 1997, and 2003. Whitehall II is an ongoing study of 6,895 men and 3,413 women, aged 35-55 years in 1985; follow-up examinations were conducted in 1991 (n = 8,815), 1997 (n = 7,870), 2003 (n = 6,967), 2007 (n = 6,967), 2012 (n = 6,318), and 2015 (n = 5,632) with each wave taking 2 years to complete. Both SBP and DBP were measured at each visit. The primary outcome, dementia incidence, was ascertained through electronic health records through 2017.
A total of 8,639 adults (32.5% women) were included in the present analysis. Dementia was identified through electronic medical records in 385 participants. Mean age at dementia diagnosis was 75.2 (standard deviation, 5.4) years. Incidence of dementia was associated with lower education, higher BP, and co-morbidities. SBP ≥130 mm Hg at age 50 was associated with an increased risk for dementia. However, SBP ≥130 mm Hg at age 60 or 70 was not associaterd with dementia. After adjustment for factors including sociodemographic characteristics, health behaviors, and time-varying chronic conditions, having a SBP ≥130 mm Hg increased the risk for dementia significantly (hazard ratio [HR], 1.38; 95% confidence interval [CI], 1.11-1.70) compared to SBP <130 mm Hg. DBP was not associated with dementia. Participants with longer exposure to hypertension (SBP ≥130 mm Hg) between mean ages of 45 and 61 years had an increased risk of dementia compared to those with no or low exposure to hypertension (HR, 1.29; 95% CI, 1.00-1.66). In multi-state models, SBP ≥130 mm Hg at 50 years of age was associated with greater risk of dementia in those free of CVD over the follow-up (HR, 1.47; 95% CI, 1.15-1.87).
The authors concluded that SBP ≥130 mm Hg at age 50, below the conventional ≥140 mm Hg threshold used to define hypertension, is associated with an increased risk of dementia; in these persons, this excess risk is independent of CVD.
These data support the identification and treatment of SBP ≥130 mm Hg to improve health during the aging process, including reducing risk for dementia.