Systolic inter-arm blood pressure difference and cognitive decline: Findings from the INTERPRESS-IPD Collaboration
Hypertension and dementia are associated with older age and with each other. As the populations age, numbers of individuals living with dementia will rise, representing substantial costs and care burdens for society. Currently, there are no interventions to halt established cognitive decline, therefore approaches focus on prevention. Systolic inter-arm difference in blood pressure (IAD) and cognitive decline are both associated with cardiovascular disease. We therefore propose, and recently published initial evidence for, associations of IAD with prospective cognitive decline. We now present findings from the Inter-arm blood pressure difference individual participant data Collaboration (INTERPRESS-IPD), examining associations of IAD with development of mild cognitive decline (MCI) and dementia.
Individual participant data meta-analyses: we examined time to event data for new diagnoses of MCI and dementia, according to IAD status in univariable and multivariable Cox regression models, stratified by study. Multivariable analyses were adjusted for systolic blood pressure, age, sex and highest educational attainment. We also examined changes in Mental State Examination (MSE) scores, with adjustment for all of the above and duration of follow up.
Mean age was 66.2 (SD 11.9) years, 55% of participants were female, 84% were of White ethnicity and mean systolic IAD was 7.0 (7.5) mmHg. During 10 years of follow up, there were 273 (5.9%) new diagnoses of MCI among 4,635 participants, from 3 cohorts. In univariable analyses, MCI was associated with a systolic IAD ≥ 5mmHg (Hazard Ratio (HR) 1.34 (95%CI 1.04 to 1.72); p=0.022) and IAD ≥ 10mmHg (HR 1.33 (1.03 to 1.73); p=0.032). After adjustment, the associations remained: HR 1.31 (1.02 to 1.67; p=0.036) for IAD ≥ 5mmHg and HR 1.29 (0.99 to 1.68; p =0.056) for IAD ≥ 10mmHg. No significant associations were observed above an IAD of 10mmHg. There were 95 (2.0%) new diagnoses of dementia during follow up; no associations were observed between diagnosis of dementia and IAD.MSE scores were recorded for 2,709 participants in 3 cohorts; 419 (15.5%) showed clinically meaningful reductions (i.e. ≥ 5 points) during follow up. Decreases were associated with an IAD ≥ 5mmHg (p=0.004) and IAD ≥ 10mmHg (p=0.006) on univariable analyses. After adjustment the association with an IAD ≥ 5mmHg remained (p=0.033); age and educational attainment attenuated the association with an IAD ≥ 10mmHg (p=0.11).
We present the first time-to-event analyses of development of MCI with IAD. These data provide additional evidence that systolic IADs ≥5mmHg and ≥10mmHg are associated with development of MCI in a pooled cohort of >4,000 participants. Work to enlarge the dataset and extend these analyses continues. Measurement of blood pressure in both arms is recommended and is straightforward; confirmation of these findings could inform individualised treatment decisions to minimise risk of future cognitive decline.