Relationship between blood pressure and cognitive decline: a 4-year community-based prospective cohort study

Objective To explore the relationship between blood pressure at baseline and significant decline in cognitive function after 4 years in middle-aged and elderly people in rural Xi'an, and the potential effect of age on the relationship. Methods Data were collected from a cohort of middle-aged and elderly people with cognitive impairment in rural Xi'an, Shaanxi Province. The cohort consisted of people aged ≥40 years from a village in Huyi District, Xi'an. The baseline survey was completed between October 2014 and March 2015, and two follow-up visits were conducted in 2016 and 2018. Blood pressure parameters studied included hypertension and high systolic blood pressure (≥140mmHg vs.＜140mmHg), and high diastolic blood pressure (≥90mmHg vs.＜90mmHg). The Mini-Mental State Examination (MMSE) was used to assess the whole cognitive function, and the decline of MMSE score ≥4 points in 4 years was defined as significant decline of cognitive function. Multivariate Logistic regression was used to analyze the relationship between blood pressure and cognitive function at baseline.Subgroup analysis was used to study the effect of age (＜65vs.≥65years) on the relationship. Results Werecruitedatotalof1350 subjects in the analysis, including 235 subjects (17.4%) with baseline age ≥65 years and 533male subjects (39.5%) ；671 subjects (49.7%) had hypertension, with systolic blood pressure of (131.71±17.79)mmHg；840 subjects (62.2%) had high systolic blood pressure, with diastolic blood pressure of (82.18±10.56)mmHg；395 (29.3%) had high diastolic blood pressure.During the 4-year follow-up, 56 cases (4.2%)met the criteria for significant decline of cognitive function.We did not find significant association of hypertension and high systolic blood pressure with cognitive decline in the general population, ＜65-year-old subgroup, or ≥65-year-old subgroup. The incidence of significant cognitive decline was not statistically significant in the total population (3.6%vs.5.6%, P=0.092), the≥ 65-year-old subgroup (7.5%vs.8.2%, P=0.855), the normal diastolic blood pressure group, or the high diastolic blood pressure group. However, in the subgroup＜65 years, the incidence of cognitive decline was higher in the high diastolic blood pressure group than in the normal diastolic blood pressure group (2.7%vs.5.1%, P=0.043). Multivariate analysis showed that high diastolic blood pressure was not found to be associated with significant cognitive decline in the total population (OR=1.744, 95%CI ：0.953-3.192, P=0.071), the subgroup of ≥65 years old (OR=0.858, 95%CI ：0.221-3.338, P=0.825), or the subgroup of≥65 years old.In the＜65 age group, high diastolic blood pressure was significantly associated with cognitive decline (OR=2.051, 95%CI ：1.005-4.186, P=0.048). Conclusion High diastolic blood pressure is associated with 4-year cognitive decline in people aged 40-65 years, but not in those aged ≥65. No association is found between hypertension or high systolic blood pressure and significant cognitive decline.