Systolic Blood Pressure and Cognitive Decline in Older Adults With Hypertension

Streit et al. has established an association between treating hypertension between 140 to 160 mmHg and an increased rate of cognitive decline, among the frail elderly. In doing so, they have provided evidence against a common trend in general practice, the one-size-fits-all approach, that hypertension must be managed in all patients. By including the frail elderly in their study population, Streit et al.'s study fills the gap for this rarely investigated population. They have brought to attention current limitations of various hypertension guidelines, the cognitive risks of hypertension management, and provided information to update our current understanding of hypertension in the frail elderly.

Current treatment guidelines provide a one-size-fits-all approach to managing hypertension, by not distinguishing between the frail and non-frail. The American Heart Association (AHA) and American College of Cardiology (ACC) provide regularly updated hypertension management guidelines (Welton et al., 2018). Their recent update in their guidelines further reinforces this one-size fits all trend, going in the opposite direction of Streit et al.'s findings. They now recommend, that the systolic BP at which treatment should be initiated be lowered from 140 to 130mmHg (Welton et al., 2018). Furthermore, in their discussion of BP and dementia, they suggest that lowering BP will delay the onset of dementia and that there are no studies showing an adverse impact on dementia incidence or cognitive function (Welton et al., 2018). Although we do not oppose their conclusions that timely hypertension management may delay the onset of dementia, we do note that they fail, however, to distinguish between the frail and non-frail elderly, as Streit et al. have managed to do.

The Hypertension Canada Guidelines publishes yearly updated evidence-based guidelines for managing hypertension. In their 2017 guidelines, they removed the alternate BP targets in the frail and elderly (Leung et al., 2017). Their updated recommendations recommend using the average systolic BP of 140 rather then 160 mmHg as cut off to initiate medical management, noting the lack of clinical trials involving the frail elderly population (Leung et al., 2017).

Compounding the trend of aggressive BP treatment in the old age population regardless of frailty, is the fact that cardiovascular disease is a predictor for Alzheimer disease progression (Schmidt et a., 2011). Following this logic, it makes sense that family physicians pursue its aggressive management as an attempt to reduce the risk or rate of neurocognitive decline, no matter the age and comorbidities. However, in the frail elderly with longstanding hypertension, perhaps they have not retained sufficient cerebral vascular autoregulation to adapt to a medically induced normalised blood pressure, and therefore assure their pre-treatment rate of cerebral perfusion (Alosco et al., 2014).

Knowledge transition describes the implementation of the latest knowledge to current evidence-based practice, and allows us to practice medicine to our best of our knowledge. The lack of distinction between frail and non-frail patients in current guidelines can be traced to the omission of these difficult patients from clinical trials, and highlights the tendency of making generalisations based on the best available current data. The findings by Streit et al. add to our current knowledge-base, and will surely be considered in future updates of hypertension guidelines throughout the world. Streit et al.'s findings are a reminder that medical knowledge is not absolute but evolving, and that, as the old adage goes, doing nothing is sometimes doing something.

References:

Alosco et al., The impact of hypertension on cerebral perfusion and cortical thickness in older adults. J Am Sco Hypertens. 2014;8(8):561-570.

Leung A, Daskalopoulou S, Dasgupta K. et al. Hypertension Canada's 2017 Guidelines for Diagnosis, Risk Assessment, Prevention, and Treatment of Hypertension in Adults. Can J Cardiol. 2017 May;33(5):557-576.

Schmidt C., Wolff M., Weltz M., Bartlau T., Korth C., Zerr, I. Rapidly progressive Alzheimer disease. Arch Neurol. 2011; 68(9):1124-30.

Whelton, P., Carey, R., Aronow, W. et al. 2017ACC/ AHA/ AAPA/ ABC/ ACPM/ AGS/ APhA/ ASH/ ASPC/ NMA/ PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults. A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Journal of the American College of Cardiology. 2018; 71(19)

Competing interests: None declared

The purpose of this study was to compare the effects of different standards of blood pressure control on the cognitive/daily functions of life and quality of life outcomes in patients with complex health conditions. The authors aimed to see if less strict blood pressure control was associated with more positive outcomes for patients. The authors analyzed EMR data from the Integrated Systematic Care for Older Persons (ISCOPE). The population of patients studied were individuals over 75 years old with hypertension from the Netherlands. This is a cluster-randomized prospective cohort study that investigated if systolic BP (SPB) greater than 130 mmHg, when under monitored and regulated medical control, has effects on cognitive function and quality of life in patients over 75 years of age when compared to those who are not on antihypertensive medications.

Inclusion criteria for the study were consent to EMR data, the ability to attribute the patient's EMR data to the data set being analyzed, selection for one year follow-up in ISCOPE, and that the patient's systolic blood pressure was measured a year prior to ISCOPE inclusion. Exclusion criteria was limited to terminal illness or projected life expectancy less than 3 months. The authors attempted to identify potential data confounders: living situation, income, education, non-cardiovascular comorbidities (cancer, diabetes, depression), and cardiovascular (CVD) disease comorbidities (myocardial infarction, angina pectoris, intermittent claudication, cerebral vascular accident, transient ischemic attack, heart failure, and other ischemic heart disease). The aforementioned variables were statistically insignificant and did not meet the confounder criteria between the authors' crude and adjusted data sets, minimizing the variable's effects on statistical models.

The authors utilized the Mini-Mental State Exam (MMSE) in order to assess cognitive function, on a scale of 0 - 30 points, with a higher score indicating increased cognitive function, and 27 - 30 being within normal range of cognition. For the patients on antihypertensive medications with SPB less than 130 mmHg, their 1-year average cognitive decline was 0.90 points on MMSE, and for the patients on antihypertensives with SBP over 150 mmHg, their 1-year average cognitive decline was 0.14 on MMSE, which the authors suggested was due to the stricter SBP management contributing to increased 1-year cognitive decline. For the patients not on antihypertensive medications, there was a similar trend observed, but the data was not clinically significant.

In order to assess participant functionality with basic and instrumental activities of daily life (ADLs), the authors utilized the Groningen Activity Restriction Scale (GARS), with the combined scores ranging from 18 - 72 points, and a higher score indicating increased disability. For measurement of participant quality of life (QoL), the authors utilized the EQ-5D-3L index, in which the patient's subjectively rated their current health status by 5 main categories; mobility, ADLs, pain and discomfort, anxiety and depression, and self-care, and a value was generated using the EuroQoL group, where full health is valued at 1 and death is valued at 0. The authors of the study did not find an association between SBP and effects on ADLs or QoL for patients on or without antihypertensive therapy.

The study population of this report included 1,266 participants, with an average age of 82.4 years. About 84% of the participants were undergoing current antihypertensive therapy. Initial socio-demographic characteristics of the study population with and without antihypertensive therapy were similar, however those with antihypertensive therapy had higher rates of SBP greater than 150 mmHg, CVD, diabetes, and a lower QoL. Discussion by the group on these population characteristics included the mismatch between population who were females (69%) and those male (31%), as the group would have liked to see a more even split. Further discussion by the group noted the percentage of low-income persons in the study population (16%), and due to The Netherlands having a universal healthcare program, it can be implied that low-income individuals have fewer barriers to quality healthcare, as compared to a more diverse general population found in a country like the United States.

At a one year follow up of the study population, the authors reported a descriptive trend across every observed category of SBP, where with lower SBP there was worsening of cognitive decline as measured by MMSE. In comparison of the populations with and without antihypertensive therapy, there were higher rates of cognitive decline (based on MMSE) for the group not receiving antihypertensive therapy across every SBP grouping. There was no clear association found between both study populations with either QoL nor daily functioning. These findings were similar for participants with complex healthy problems.

The group discussed these findings, with particular focus on the use of validated rating instruments for cognitive decline (MMSE), daily functioning (GARS), and QoL (EQ-5D-3L). The use of validated tools for assessing key outcomes was reassuring in terms of inter-rater accuracy and reproducibility. The group further discussed the paradoxical relationship between SBP control and quality outcomes. Generally, tighter BP control is recommended for improvement of health outcomes. However, this study did not show this association in its results, but quite the opposite.

Furthermore, the results from this study are not the first instance in which an association has been shown between strict medication regimen and control of patient metabolics and increased rates of patient morbidity. A New England Journal of Medicine publication, Intensive versus Conventional Glucose Control in Critically Ill Patients by S. Finfer et al (March 26, 2009), showed that adults in the intensive care unit for three or more consecutive days had increased morbidity and mortality when physicians utilized more intensive glucose control ranging between 81-108 mg/dL, as compared to those of 180 mg/dL or less. Although Finfer et al did not compare blood glucose to patient's cognitive ability, there seems to be an association with tight medical regulation of a patient's blood glucose and detrimental effects to a patient's well-being. Similar to the results reported by Streit et al, there seems to be beneficial effects to patient health associated with a less stringent medication regimen for a patient's hypertension and blood glucose.

Competing interests: None declared