Association between cumulative blood pressure and the risk of cognitive impairment in Chinese older adults: a longitudinal study over 16 years

Cumulative blood pressure (BP), which takes into account both the magnitude and duration of BP exposure, is linked to cognitive impairment. However, this association remains unclear in Chinese older adults. The critical level of cumulative BP associated with significantly increased cognitive impairment risk remains elusive. Thus, this study aims to investigate the association between cumulative BP levels and the risk of cognitive impairment in Chinese older adults. The Chinese Longitudinal Healthy Longevity Survey (CLHLS) over 16 years was divided into two consecutive sub-cohorts, namely the 2002 sub-cohort from 2002 to 2011 and the 2008 sub-cohort from 2008 to 2018. Cumulative BP exposures were calculated as the area under the curve derived from two consequence BP measurements and their corresponding time intervals. Cognitive impairment was defined according to the years of schooling and total cognitive scores of older adults during the follow-up periods. Hazard ratios (HRs) with 95% confidence intervals (CIs) for the risk of cognitive impairment across quartiles of cumulative BP were estimated using multivariable Cox proportional hazard models. Finally, potential dose-response relationships were examined using restricted cubic splines. A total of 2,142 and 1,920 cognitively healthy older adults participants from the two sub-cohorts were included in the analysis, respectively. Over a median follow-up of 6.2 years (IQR 6.1–6.3) and 7.0 years (IQR 6.8–7.2), 542 and 347 older adults experienced cognitive impairment in the two sub-cohorts, respectively. Higher cumulative systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure (PP) were significantly associated with a higher risk of cognitive impairment (all Ptrend <0.01). Compared to the lowest quartile in the two sub-cohorts, the HRs (95%CIs) for cognitive impairment risk in the highest quartile were 1.85 (1.33–2.59) and 2.64 (1.76–3.97) for cumulative SBP, 2.00 (1.45–2.75) and 2.20 (1.46–3.33) for cumulative DBP, and 1.59 (1.16–2.18) and 2.10 (1.42–3.10) for cumulative PP, respectively. Linear dose-response patterns were observed for the association between the risks of cognitive impairment with all three cumulative BP levels in both two sub-cohorts. Moreover, cumulative SBP increased from 387.8 mm Hg × year to 416.4 mm Hg × year over 6 years, whilst cumulative PP increased from 138.7 mm Hg × year to 170.8 mm Hg × year—equivalent to a mean SBP increase from 131.0 mm Hg to 134.8 mm Hg and mean PP increase from 46.9 mm Hg to 55.3 mm Hg—which collectively increased the risk of cognitive impairment. In contrast, cumulative DBP was maintained at 245 mm Hg × year over 6 years, whereas the mean DBP progressively decreased from 82.9 mm Hg to 79.3 mm Hg, showed a significant association with cognitive impairment. Elevated cumulative SBP, DBP, and PP independently increased subsequent cognitive impairment risk in Chinese older adults.