Cognitive Impairment After Stroke

I. INTRODUCTION

Topic Background

Stroke comprises a major morbidity and mortality in both developed and developing countries [1]. In 2008, stroke was the leading cause of mortality in the United States and was the leading cause of long-term severe disability [2]. In Japan and other Asian countries, the percentage of ischemic stroke is higher than in the west [3]. Stroke ranked as the second leading cause of death after heart disease in the Philippines and the mortality rate is increasing in both sexes [4].

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Stroke may cause physical and cognitive impairments [5]. Cognitive impairment occurs three months after stroke in 35.2% to 43.9% of patients and may continue for a long time in almost one third of patients [6-8]. Hospital-based and population-based studies [6,7] have shown a substantial risk for developing delayed dementia even among patients who remain cognitively intact after their index stroke. However, motor deficits rather than cognitive deficits attract most attention after stroke, and patients with stroke with problems in cognition frequently do not receive medical treatment [8]. In the Philippines, cognitive impairments occurred in 16% of patients after an acute ischemic stoke according to one study [9]. Unfortunately, there are no other local studies on this field, hence this undertaking.

Review of Related Literature

Stroke is a global problem. Over the past decades, stroke incidence went down to 42% in high-income countries and increased by more than 100% in low and middle-income countries. Stroke incidence in low and middle-income countries now surpasses those in high-income countries [10].

Cognitive impairment often develops after stroke and its prevalence ranges from 20% to 80% [11]. Snaphaan and colleagues in 2007 reported that post-stroke cognitive impairment varied from 23% to 55%, three months after stroke and dropped to 11% to 31% one year after stroke [12]. A stroke cohort study showed that 30% of patients with stroke who had mild cognitive impairments (MCI) improved between zero to six months and became cognitively intact by 12 to 18 months after stroke [13]. Douiri PhD et al. in 2013 noted that the overall prevalence of cognitive impairment remained relatively unchanged three months after stroke and at yearly follow up, at 22% at three months, 22% at five years and 21% at 14years. Studies evaluating the course of cognitive decline over time showed a 10 to 15 percent annual rate conversion of MCI to dementia [14].

The risk of cognitive impairment post-stroke is related to the demographic aspects such as age, sex, education and occupation and vascular factors [11]. Studies found that the prevalence of MCI increased with age [15,16]. Petersen, PhD, in 2010 noted that the prevalence of MCI is higher in men than in women across all ages [15]. In contrast, a French study and Italian study revealed a greater prevalence of MCI in women compared to men [17,18].

Increasing number of years of education markedly decreased the prevalence of MCI. Petersen, PhD, MD et al. in 2010 noted that the prevalence of MCI had decreased from 30.2% to 11.0% in subjects less than nine years of education and in more than 16 years of education respectively [15]. A low socio-economic status is also an important risk factor for a number of undesirable health outcomes, including cognitive and functional impairment [19-24]. Basta et al. in 2007 pointed out that persons living in underprivileged areas were found to have a greater prevalence of cognitive impairment compared to those living in well-off regions [25].

Hypertension is correlated to a higher risk of MCI [24]. There is proof that non-amnestic MCI is associated with cerebrovascular disease and vascular cognitive impairment. Since hypertension is associated with a greater risk of stroke and vascular dementia, [26,27] it appears rational that it is associated with the risk for non-amnestic MCI such as frontal-executive cognitive impairment [24].

Luchsinger, MD et al. in 2007 pointed out that the probability of MCI secondary to diabetes was higher in African American and Hispanic persons. However, the prevalence was lower in non-Hispanic white persons, indicating the greater occurrence of diabetes in marginal populations in the United States. Diabetes was associated with a greater risk of amnestic MCI even when adjusting for stroke and vascular risk factors, which denotes that the association between diabetes and amnestic MCI is independent of cerebrovascular disease. Contrariwise, the association of diabetes to non-amnestic MCI was substantially reduced and became non-significant after adjusting for stroke and vascular risk factors [28].

Patients with familial hypercholesterolemia revealed greater prevalence of MCI compared with those without familial hypercholesterolemia. Previous reports revealed that older patients with sporadic hypercholesterolemia did not show a higher incidence of MCI, suggesting that early exposure to high levels of cholesterol or LDL receptor dysfunction may be at risk for developing MCI [29].

Hansen, et al. in 2012 noted that white matter lesions (WML) were appreciably linked with impaired executive function and memory [19]. Major deficits on measures of attention and other executive functions were identified in a set of subjects with severe WML implying that a threshold for the total area of WML must be exceeded before cognitive deficits ensue. Smaller total areas of WML are being needed to produce cognitive deficits when critical locations are involved [20].

A large study in 2000, found that subcortical and periventricular WML have been associated with lesser performance on cognitive measures, mainly those related to psychomotor speed [21]. Similar association between periventricular WML and processing speed were reported in the studies of Ylikoski et al. and Fukui et al [22,23].

Tatemichi et al. in 1994 found that cognitive domains that had been commonly affected in stroke were memory, orientation, language and attention as compared with control subjects. Among stroke patients, cognitive impairment was most often associated with infarctions in the left anterior and posterior cerebral artery territories and major cortical syndromes [30].

Detection and monitoring of MCI is vital to proper patient care [31]. In 2006, the National Institute of Neurological Disorders and the Stroke-Canadian Stroke Network recommended the Montreal Cognitive Assessment (MoCA) test, as an optimal concise protocol for the evaluation of vascular cognitive impairment [32]. This reference was centered on evidence for detecting MCI in memory clinic patients using the MoCA, also on expert opinion about the cognitive domains most affected by vascular disease. Content validity evidence implies that the MoCA assesses most of the domains that exemplify cognitive impairment in stroke. The MoCA compares equivalently and favorably to the Mini Mental Status Examination (MMSE) as a screening tool to the milder forms of cognitive impairment that follows after stroke [31]. In the 2012 Dementia and Cognitive Impairment Diagnosis and treatment Guidelines, MoCA has been one of the recommended validated cognitive assessment tools for evaluating cognitive function [33].

Though there are limits in the capability to predict the conversion from MCI to dementia [34,35], it is identified that MCI is correlated with effects at the societal, individual and familial levels [36]. At the societal level, it has been projected that the expenses related to MCI are only somewhat greater than those without MCI [37], presumably since the problem has not been scrutinized in detailed studies [36]. Conversely, it should be anticipated that as the familiarity of the syndrome advances, the costs would rise due to the development of new techniques for persons with the finding [35,38].

At the individual level, although still effective in their daily undertakings, the ones with MCI are challenged with cognitive difficulties that cause them apprehension and anguish [39-42]. Various reports have shown that individuals with MCI are faced with thoughts of societal isolation, insecurity and anxiety, which could be a consequence of the uncertainty of the diagnosis, of fear of humiliation or from reduced self-reliance [40,43].

The effects at the family level are unfavorable. Certainly, there have been a lot of reports evaluating the consequences of MCI on family caregivers [36]. A current publication covering the report up to July 2011 denoted that the most frequently felt emotions stated by caregivers were frustration, guilt and anger [39]. Additional consequences are a strong sense of loss [44] and lack in the caregiver connection with the patient [45], including a less efficient interaction, a loss of affection [39,46], and reduced marital desire among spouses [47].

The Southern Philippines Medical Center (SPMC) is a government hospital in Davao City under the Department of Health, with a 1,200-bed capacity. An average of 157 stroke patients are being admitted per month or approximately 1,884 annually under the Internal Medicine Department. An average of 139 stroke patients is consulting per month or approximately 1,668 annually at the Outpatient Neurology Clinic. Cognitive deficits are not routinely checked in our stroke patients. Hence, this study is conducted to add knowledge on cognitive impairment among stroke patients in this locale.

Research Question

What is the prevalence of cognitive impairment among stroke patients in a tertiary hospital in Davao City?

Significance of the Study

Most studies of stroke outcomes have focused on physical consequences and few have examined intellectual deficits. MCI has been given much scientific attention due to its higher risk to progress to dementia. Because early intervention, such as controlling the vascular risk factors and initiation of pharmacologic treatment, would be helpful in slowing the rate of decline in cognitive function. Therefore, it is important to detect vascular dementia at an early stage. In SPMC, there is no study yet regarding cognitive impairment among stroke patients. Determining the prevalence of cognitive impairment among stroke patients and the urgency in administering early therapy should be discounted in research advances.

Operational Definition of Terms

Age category:

a) 39 and below

b) 40 to 59

c) 60 and above

Cognitive domain – an area of study that deals with the processes and measurable results of study, as well as the practical ability to apply intelligence.

Comorbidities – are conditions that coexist with a primary disease.

1. Hypertension
2. Diabetes
3. Hypercholesterolemia
4. Hypertension and Diabetes
5. Hypertension and Hypercholesterolemia
6. Diabetes and Hypercholesterolemia

Dementia – is a disorder characterized by problems with memory and at least one cognitive function (learning, reasoning, language, spatial ability and orientation, and handling complex tasks) that are severe enough to interfere with activities of daily living.

Diabetes – a person with fasting plasma glucose (FPG) 126 mg/dL or A1C 6.5% or random plasma glucose 200 mg/dL.

Educational attainment:

a) elementary

b) high school

c) college

Hypercholesterolemia – a person with a low density lipoprotein (LDL) of 100mg/dL.

Hypertension – a person with a blood pressure (BP) of140/90.

Income: (based on National Statistics Office)

1. Low-income – are people or families earning less than 65,787 per year.
2. Middle-income – are people or families earning between 65,787 to 805,582 pesos per year.
3. High-income – are people or families earning more than 805,582 pesos per year.

Mild cognitive impairment – is a cognitive decline greater than expected for an individual’s age and education level that does not interfere notably with activities of daily living.

Montreal Cognitive Assessment – is a rapid screening instrument for mild cognitive dysfunction.

Stroke –is an abrupt onset of a neurologic deficit that is attributable to a focal vascular cause. Stroke has occurred if the neurologic signs and symptoms last for >24 hours.

General Objective

The main objective of this study is to determine the prevalence of cognitive impairment among stroke patients in a tertiary hospital in Davao City.

Specific Objectives

1. To describe the demographic profile of stroke patients in a tertiary hospital in Davao City, in terms of:
   1. Age
   2. Sex
   3. Educational attainment
   4. Income
   5. Medical comorbidities
   6. Location/extent of stroke
2. To assess different cognitive domains:
   1. Attention and concentration
   2. Executive function
   3. Memory
   4. Language
   5. Visuospacial skills
   6. Abstraction
   7. Calculation
   8. Orientation
3. To determine the relationships between demographic profiles and cognitive impairment.