|ORIGINAL RESEARCH REPORT
|Year : 2017 | Volume
| Issue : 4 | Page : 193-199
Evaluation of oxidative stress and cognitive function status of elderly hypertensive patients
Philip Alaba Adebola1, Abidemi James Akindele2, Sunday O Olayemi2
1 Department of Medicine, LASUTH/LASUCOM, Ikeja, Nigeria
2 Department of Pharmacology, LUTH/CMUL, Idi-Araba, Lagos, Nigeria
|Date of Web Publication||8-Nov-2017|
Philip Alaba Adebola
Department of Medicine, LASUTH/LASUCOM, Ikeja, Lagos
Source of Support: None, Conflict of Interest: None
Background: Elderly hypertensive patients have been reported to be particularly at the risk of cognitive dysfunction because of several factors. The previous studies in both rats and humans suggest that some classes of antihypertensive drugs could ameliorate the cognitive decline in elderly hypertensive patients. Most of these studies were among Caucasians in the Western world. This study was aimed at evaluating the oxidative stress and cognitive function status of elderly hypertensive Nigerians on regular antihypertensive drugs. Methods: One hundred and eight elderly hypertensive Nigerians of both gender who were 60 years old and above, were controlled with different antihypertensive drugs, and were enrolled into the study. All had cognitive function status evaluation using the Mini-Mental State Examination (MMSE) score. Totally 98 of the elderly hypertensive patients also had their oxidative stress status evaluated by measurement of their serum antioxidant levels. 33 elderly normotensive Nigerians were used as controls. Results: The elderly hypertensives had a significantly higher mean MMSE cognitive score of 27.97 ± 1.70 compared to the elderly normotensives with score of 26.97 ± 2.44 (P = 0.001). The elderly hypertensive patients had significantly higher mean level of serum antioxidants – catalase, superoxide dismutase, reduced glutathione, and glutathione peroxidase, compared to the elderly normotensive individuals (P < 0.01). Patients on calcium channel blockers had higher mean serum antioxidants level than patients on other classes of antihypertensive drugs. Conclusion: The present study suggests that elderly hypertensive Nigerians who were controlled with regular antihypertensive drugs, had better cognitive function and lower oxidative stress status than their normotensive counterparts.
Keywords: Antihypertensive drugs, cognitive status, elderly hypertensive, oxidative stress
|How to cite this article:|
Adebola PA, Akindele AJ, Olayemi SO. Evaluation of oxidative stress and cognitive function status of elderly hypertensive patients. J Clin Sci 2017;14:193-9
|How to cite this URL:|
Adebola PA, Akindele AJ, Olayemi SO. Evaluation of oxidative stress and cognitive function status of elderly hypertensive patients. J Clin Sci [serial online] 2017 [cited 2020 Jan 20];14:193-9. Available from: http://www.jcsjournal.org/text.asp?2017/14/4/193/217814
| Introduction|| |
It is a known fact that elderly hypertensive patients are prone to progressive cognitive function impairment as they grow older because of a multiplicity of factors. These factors include accelerated atherosclerosis leading to progressive multi-infarct dementia, increased oxidative stress, and increasing risk of age-related neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease.,, Several earlier studies have documented the fact that elderly hypertensive patients have greater prevalence of cognitive functions impairment when compared to their normotensive counterparts. Most of these studies with, few exceptions, were done among Caucasians.,,,,
There is evidence that antihypertensive drugs such as calcium channel blockers (especially 2nd-and 3rd-generation agents, i.e., amlodipine, felodipine, lacidipine, etc.) and angiotensin-receptor blockers (i.e., losartan, candesartan, and telmisartan,) could prevent or retard the progression of cognitive function impairment and the development of neurodegenerative disorders in the hypertensive patient.,,, Calcium channel blockers prevent excess calcium entry into the cell and thereby preventing cellular neuronal damage and apoptosis. Calcium channel blockers have also been reported as being able to reduce oxidative stress., A high level of oxidative stress is a well-documented precursor to cellular damage and neuronal loss. Angiotensin-receptor blockers selectively block angiotensin 1 receptors in the brain and thereby preventing long-term angiotensin 1-mediated cerebrovascular dysfunction. There are conflicting reports concerning the effect if any, of other antihypertensive drugs such as β-adrenergic-receptor blockers (β-blockers), diuretics, etc. on the cognitive function of elderly hypertensive patients.,,
The present study was aimed at comparing the oxidative stress level and cognitive function of adult elderly hypertensive patients on calcium channel blockers, angiotensin-converting enzyme inhibitors/receptor blockers, and other antihypertensive drugs to that of their age and education-matched normotensive counterparts.
| Methods|| |
The study was a cross-sectional study of elderly hypertensive patients on regular antihypertensive drug therapy. The study was carried out in the Medical Outpatient Clinic. All the participants were required to give informed consents before being enrolled into the study. Ethical approval for the study (No: LREC/10/06/347) was obtained from the Ethics Committee before the commencement of the study.
Elderly hypertensive Nigerians aged 60 years and above. The hypertensive patients were on regular antihypertensive drug therapy for at least 3 months before being enrolled into the study.
Patients with uncontrolled hypertension blood pressure (BP) ≥150 mmHg systolic, established neurodegenerative disorder, for example, Alzheimer's and Parkinson's diseases, positive history suggestive of a stroke, established clinical diagnosis of depression or other psychiatric ailments, known diabetics, established thyroid or other hormone-related disorders, history of alcohol intake greater than 2 units of alcohol per day, and clinical evidence of cardiac decompensation/heart failure were all excluded from the study. Patients with obvious debilitating chronic ailments from any cause and patients who were unable to read and write or without any formal education were also excluded from the study.
A total of 108 hypertensive Nigerians aged 60 years and above, consisting of 44 male and 64 female hypertensive patients on regular antihypertensive drugs medication for at least 3 months before the study, were enrolled in the study. Thirty-three age and education-matched elderly normotensive Nigerians were selected as controls for the study. The sample size of the controls was relatively small because of the difficulty of finding elderly normotensive individuals within the period of the study. Since there is a paucity of literature on this subject in Nigeria, the sample size was mainly determined by cost and logistics considerations.
Questionnaires containing relevant information on the participants such as age, gender, level of education attainment, alcohol and cigarette usage, diabetic status, duration of hypertensive status and types of antihypertensive drug medication, were administered to all the participants enrolled into the study. The baseline BP of each subject using the standard mercury sphygmomanometer was documented. The Mini-Mental State Examination (MMSE) for the determination of cognitive function was administered to each subject and the individual total score was recorded at the time of the study.,, The MMSE is an 11 question measure that tests five areas of cognitive function: orientation, registration, attention and calculation, recall, and language. The maximum score is 30. For the purpose of the present study, individuals with score of 28 and above were classified as having normal cognition while individuals with score of 27 or less were classified as having impaired cognition or cognitive dysfunction.
Blood samples were taken for the estimation of the level ofin vivo antioxidants including catalase (CAT), superoxide dismutase (SOD), reduced glutathione (GSH), and glutathione peroxidase (GPx) at the time of the study. About 5 ml of venous blood samples from the participants were drawn into universal plain bottles by qualified medical personnel. The blood samples were immediately taken to the laboratory for centrifuge, and the serum generated was stored in the deep freezer at temperature of −25°C. Assay ofin vivo antioxidants (CAT, SOD, GSH, and GPx) was done using established methods.,
This was done using SPSS 16.0 software package (SPSS IBM Version 20). Parametric data were analyzed using Student's t-test while nonparametric data were analyzed using Chi-square test. The level of significant P value was set at <0.05.
| Results|| |
A total of 108 elderly hypertensives with mean age of 65.4 ± 5.6 years (range 60–82 years), consisting 44 males and 64 females, participated in the study. A total of 33 elderly normotensive individuals with mean age of 64.4 ± 5.2 years (range 60–78 years), consisting of 17 males and 16 females, were evaluated as controls for the study. All the hypertensive participants had cognitive function status evaluation using the MMSE scale while 98 of the hypertensive participants had blood sample estimation forin vivo antioxidants. All the normotensive control participants had cognitive function status evaluation while 29 of them also had blood sample estimation forin vivo antioxidants. The levels of education attained by the hypertensive and control subjects were evenly spread between primary, secondary, and tertiary education [Figure 1]a and [Figure 1]b. A total of 20 out of the 108 hypertensives took alcohol moderately while 16 out of the 33 control subjects took alcohol. Only 4 and 5 of the hypertensive and normotensive control subjects, respectively, had positive history of cigarette smoke.
|Figure 1: (a) Distribution of elderly hypertensive patients according to educational status. (b) Distribution of elderly normotensives according to educational status|
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Forty-five out of the 108 elderly hypertensive participants (41.6%) had been diagnosed with systemic hypertension for at least 10 years while 72 out of the 108 elderly hypertensives (66.6%) had been diagnosed for at least 5 years. Only 4 of the hypertensives were diagnosed to be hypertensive within 1 year before the study. All the hypertensives were controlled and were on regular conventional antihypertensive medication for at least 3 months before this study. Forty of the hypertensives were on calcium channel blockers monotherapy (mainly amlodipine) while 26 of the hypertensives were on angiotensin-converting enzyme inhibitors/angiotensin-receptor blockers (ACEI/ARB) monotherapy (mainly lisinopril or losartan). Twenty eight of the hypertensives were on a combination of calcium channel blockers with ACEI/ARB while only 14 were on other antihypertensive medications such as β-blockers, α-methyldopa, or thiazide diuretics.
The mean MMSE cognitive function score of the hypertensives was 27.97 ± 1.70 compared to that of the normotensive control of 26.97 ± 2.44 (P = 0.001). There was no significant difference in the mean cognitive function status of hypertensive subgroups based on gender, education, type of antihypertensive medications alcohol intake, and cigarette smoking [Table 1]. Thirty-five out of the 108 elderly hypertensives (32.4%) had cognitive impairment (MMSE score ≤27) as compared to 16 out of the 33 controls subjects (48.5%) with cognitive impairment. There was no significant difference in the prevalence of cognitive impairment among the elderly hypertensive patient's subgroups [Table 2].
|Table 1: Mean cognitive function status (mini.mental state examination) of elderly hypertensive subgroups|
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|Table 2: Test of associations between cognitive function status and selected variables|
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Hypertensive patients had significantly higherin vivo antioxidants (enzymatic - SOD, CAT, and GPx; nonenzymatic - GSH) compared to that of the control subjects [Table 3]. Hypertensive patients with history of moderate alcohol intake (≤2 units/day) had consistently higher levels of antioxidants compared to the hypertensives that did not take alcohol. There was no significant difference in the mean level of the various antioxidants among elderly hypertensive patients on the different classes of antihypertensive drug medication [Table 4]. However, patients on calcium channel blockers consistently had higher mean antioxidant levels compared to patients on other antihypertensive drug combination. There was no significant difference in the mean antioxidants level of the elderly hypertensives with normal cognitive status (MMSE >27) compared to elderly hypertensive with impaired cognitive function status (MMSE ≤27). There was no significant, consistent correlation between antioxidants level and cognitive function status in elderly hypertensive [Table 5]a and b].
|Table 3: Comparison of the level of in vivo antioxidants among elderly hypertensive patients and elderly normotensive controls|
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|Table 4: Mean comparison of oxidative stress of selected variables among hypertensive subjects|
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|Table 5a: Comparison of the mean oxidative stress scores of hypertensive with their cognitive function status|
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|Table 5b: Correlation of cognitive function and oxidative stress parameters|
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| Discussion|| |
The elderly hypertensive patients outperformed the elderly normotensive individuals in the mean MMSE cognitive function status scores. However, there was no significant difference in the prevalence of cognitive impairment (MMSE ≤27) in elderly hypertensive compared to the elderly normotensive individuals. The reason for this disparity is by no means certain. It is possible that the antihypertensive medications had insignificant beneficial effect on the cognitive function of the hypertensive patients. Further evaluation suggests that there was no significant difference in the prevalence of cognitive impairment among the hypertensive patients on the different classes/groups of antihypertensive medication. This tends to suggest that the beneficial effect of antihypertensives in this respect may not be class specific but rather due to adequate BP control as in the study population. However, it must be noted that close to 80% of the elderly hypertensive patients in the study were on calcium channel blockers and ACEI/ARBs monotherapy or combination therapy.
The previous studies suggested that even though systemic hypertension may be associated with higher risk of cognitive dysfunction in the elderly hypertensives compared to elderly normotensive individuals, the risk is much reduced with regular antihypertensive medication.,,,,,, Some of these previous studies suggest that hypertensive patients on calcium channel blockers benefit most from improved cognitive functions.,, A few studies also suggested that other antihypertensives such as ARBs and β-blockers could also have beneficial effect on cognitive function in hypertensive patients.,, Other previous studies suggest that the improvement in cognitive function and/or protection against cognitive decline in hypertensive patients is due primarily to improved BP control and not necessarily the type of antihypertensive medication.,, The study by Salas et al. revealed that cognitive function score could be used as an independent predictor of noncompliance to antihypertensive medication while the study by Jaiswal et al. showed that 3 months of regular antihypertensive therapy could improve the cognitive performance of hypertensive patients. Murray et al. in a study on 1900 hypertensive African-Americans aged 65 years and above, revealed that regular antihypertensive medication reduces the odds of developing incident cognitive impairment by 38% (odds ratio 0.62, 95% confidence interval = 0.45–0.84).
The study by Ogunniyi et al. in elderly community-dwelling Yoruba individuals did not take into consideration antihypertensive medication by the hypertensive subjects. However, of the 1753 elderly participants, 120 developed incident dementia after 6 years follow-up evaluation. The prevalence of hypertension was significantly higher in the elderly demented group compared to the elderly nondemented group (70% vs. 60.2%, P = 0.34). Higher systolic BP, diastolic BP and pulse pressure were all significantly associated with increased risk of incident dementia (P< 0.05). The study concluded that systemic hypertension was associated with increased risk of developing incident dementia in elderly Yoruba individuals and advocated treatment to lower the risk.
The elderly hypertensive patients have significantly higher level of antioxidants (enzymatic and GSH) compared to their elderly normotensive counterparts. A higher oxidative stress status with resultant reduced antioxidants level (CAT, SOD, GPx, and GSH) is expected in patients with long-standing hypertensive status.,,, However, it is expected that the hypertensive patients on calcium channel blockers should have lower oxidative stress levels with resultant high level of antioxidants. This is due to the reported antioxidant effect of calcium channel blockers, compared to hypertensives on other classes of antihypertensive.,,, This could partly explain the increased level of antioxidants seen in the hypertensive elderly patients on calcium channels blockers in the present study. However, the study did not show a significant correlation between the oxidative stress status and cognitive function status of the elderly hypertensives. It is also important to mention that other factors that could affect oxidative stress status such as supplemental antioxidant medications - Vitamin E and C were not measured by the study. Again, the question could moderate alcohol intake be a factor in oxidative stress and cognitive function status of the subjects? Even though the elderly hypertensive had consistently higher antioxidants level, there is no evidence that it affected their cognitive function status. There are conflicting reports on the effect of long-term moderate alcohol intake on the cognitive function status of the individual., However, there is overwhelming evidence that long-term excess alcohol intake could lead to significant cognitive dysfunction in late life.
The elderly hypertensive patients on antihypertensive drugs had higher mean MMSE cognitive function parameters and significantly higher mean level of antioxidants than their elderly normotensive counterparts. This suggests a possible link between the high antioxidants level, hence, lower oxidative stress status in the elderly hypertensive patients and their superior cognitive function compared to the elderly normotensive individuals. Lower oxidative stress status has been widely reported to be associated with a higher cognitive function performance, and a higher oxidative stress status has been widely reported to be associated with cognitive dysfunction.,,,, In essence, a high level of antioxidants could attenuate oxidative stress and prevent cognitive decline in the hypertensive patients. Clausen et al. reported that the use of SOD and CAT mimetics in aged mice can significantly reduce lipid peroxidation, reduce the level of reactive oxygen species, and improve their performance in the fear conditioning task.
| Conclusion|| |
The present study found that the cognitive function status of elderly hypertensive Nigerians controlled with regular antihypertensive medication was slightly better than that of their elderly normotensive counterparts. The present study also revealed that elderly hypertensive Nigerians have significantly higherin vivo antioxidants when compared to that of their elderly normotensive counterparts. This suggests a lower oxidative stress status in the elderly hypertensive Nigerians on regular antihypertensive drug medications compared to the elderly normotensive Nigerians. This could have partly accounted for the higher cognitive function status of the elderly controlled hypertensive patients compared to that of their elderly normotensive counterparts as seen in the present study.
The present study notes the relatively small sample size of the elderly normotensive control subjects when compared to that of the elderly hypertensive subjects. This was partly due to the paucity of elderly normotensive individuals in the hospital setting. The present study recognizes the well-known limitation in the interpretation and use of the MMSE score as a tool for assessing the cognitive function status of an individual even though it is the most popular and widely validated worldwide. The measurements of the four antioxidants level may not reflect the totality of the oxidative stress status of the subjects since the level of other antioxidants such as Vitamin E, C, and others are also important.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]