Blood pressure control and risk of post-stroke dementia among the elderly: A population-based screening study

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Blood pressure control and risk of post-stroke dementia among the elderly: A population-based screening study

Hao Wu^1,2†, Zhihong Ren^3†, Jinghuan Gan^4†, Yang Lü⁵, Jianping Niu⁶, Xinling Meng⁷, Pan Cai⁸, Yang Li⁹, Baozhi Gang¹⁰, Yong You¹¹, Yan Lv¹², Shuai Liu², Xiao-Dan Wang² and Yong Ji^1,2*

• ¹Country Clinical College of Neurology, Neurosurgery and Neurorehabilitation, Tianjin Medical University, Tianjin, China
• ²Tianjin Key Laboratory of Cerebrovascular and Neurodegenerative Diseases, Department of Neurology, Tianjin Dementia Institute, Tianjin Huanhu Hospital, Tianjin, China
• ³Department of Neurology, Capital Medical University Electric Teaching Hospital/State Gird Beijing Electric Power Hospital, Beijing, China
• ⁴Department of Cognitive Disorder, China National Clinical Research Center for Neurological Diseases, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
• ⁵Department of Geriatrics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
• ⁶Department of Neurology, The Second Affiliated Hospital of Xiamen Medical College, Xiamen, China
• ⁷Department of Neurology, Affiliated Traditional Chinese Medicine Hospital of Xinjiang Medical University, Urumqi, China
• ⁸Dementia Clinic, Affiliated Hospital of Zunyi Medical University, Zunyi, China
• ⁹Department of Neurology, The First Hospital of Shanxi Medical University, Taiyuan, China
• ¹⁰Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
• ¹¹Department of Neurology, Second Affiliated Hospital of Hainan Medical University, Haikou, China
• ¹²Department of Neurology, Hainan General Hospital, Haikou, China

Background: Post-stroke dementia (PSD) has adverse effects on the quality of work and life in elderly stroke survivors. There are inconsistent results on the impacts of blood pressure control on the risk of PSD in people aged 65 years and above.

Objective: This study was performed to explore whether poorly-controlled blood pressure was associated with an increasing risk of PSD.

Methods: The study population was enrolled from cross-sectional research conducted in 106 communities of rural northern China. In Phase I, a total of 7,448 people aged ≥65 years, including 830 with stroke history, completed a questionnaire, a physical examination, and a cognitive assessment. Phase II further confirmed the diagnosis of PSD. Well-controlled blood pressure was defined as an average systolic blood pressure of <140 mmHg and average diastolic blood pressure of <90 mmHg over two readings in person. Failure to meet these criteria was considered as poorly-controlled blood pressure.

Results: The crude prevalence rate of PSD among stroke survivors aged 65 years and over was 17.8% [95% confidence interval (CI) 15.2–20.4%]. Among the 830 stroke survivors, the proportions of PSD gradually increased with age and the crude prevalence rates for PSD were 10.2% (95% CI 5.6–14.9%), 14.8% (95% CI 10.1–19.5%), 18.8% (95% CI 14.1–23.5%), and 27.4% (95% CI 20.8–34.1%) in subjects aged 65–69, 70–74, 75–79 and ≥80 years, respectively. Participants in the poorly-controlled blood pressure group were more likely to suffer from PSD (28.4 vs.15.3%, P < 0.001), be older (75.81 ± 4.97 vs. 74.74 ± 5.83, P < 0.05), and have a worse cognitive level (22.26 ± 7.05 vs. 24.10 ± 6.02, P < 0.05). Compared with well-controlled blood pressure patients, poorly-controlled blood pressure in stroke survivors significantly increased risk of PSD (odds ratio = 2.20, 95% CI 1.45–3.32) after adjusting for age, gender, and education.

Conclusions: The crude prevalence of PSD among stroke survivors aged ≥65 years was 17.8% at community level. In addition to lower education level and older age, poorly-controlled blood pressure was also an independent risk factor for PSD among the elderly, which is amenable to intervention. Therefore, it is essential to control blood pressure to reduce PSD incidence.

Introduction

Stroke and dementia are both common diseases in aging societies (1, 2). People often pay attention to physical disability after stroke (3), while post-stroke dementia (PSD), doubled in the population aged ≥65 years compared to without stroke (4), is often neglected (5). Longitudinal cohorts, based on population- and hospital-based research, showed that PSD incidence increased 1.7–3.0% every year (6). With the aging of society and improved survival from stroke, the numbers of patients with PSD will increase. Although many studies have reported the prevalence of PSD, the results vary from 7% in general population to over 50.0% among hospital patients (6, 7). The sample size, study design (hospital-based or population-based studies), as well as the cognitive assessment time (after stroke 6 months or 1 year) contributed to the inconsistence and great variation. However, there have been a few epidemiological studies on PSD among the elderly at community level in China.

The risk of PSD overlaps with the risk of stroke and dementia. Current studies (8–11) revealed significant predictors of PSD, including age >65 years, low education level, previous cognitive decline, vascular risk factors, stroke features, and neuroimaging factors. Although there have been many studies with a high level of evidence, the influence of some factors on PSD occurrence remains unclear, such as high blood pressure.

High blood pressure, which affects more than 75% of people over the age of 65 years, is the leading risk factor for stroke and many other vascular diseases (12). Thus, high blood pressure likely plays an important role in PSD development, although this association remains unclear (10, 13). In several randomized clinical trials concerning the effects of blood pressure reductions on cognitive outcomes, results have generally been inconclusive (14, 15). Some research suggests that the relationship between blood pressure and dementia may be age dependent (16), with high blood pressure at midlife (age 40–64 years) being associated with an increased risk of late-life dementia (17, 18). However, there is no consensus on the association between blood pressure and dementia in those aged 65 years and above. These varied results may be attributed to differences in subtype and cause of dementia. PSD is mainly the result of ischemia of the brain parenchyma caused by atherosclerotic disease (19). Therefore, our study focuses on the relationship between blood pressure control and PSD among the elderly population, so as to explore the potential modifiable risk factors for PSD.

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