|Year : 2014 | Volume
| Issue : 2 | Page : 67-71
Prevalence of hypertension and its relationship with indices of obesity in Maiduguri, Northeastern Nigeria
Ibrahim D Gezawa1, Baba M Musa2, Muhammad S Mijinyawa1, Muhammad A Talle2, Yusuf M Shehu1, Andrew E Uloko1, MM Watila2, BM Musa1
1 Department of Medicine, Bayero University, Aminu Kano Teaching Hospital, Kano, Nigeria
2 Department of Medicine, University of Maiduguri Teaching Hospital, Maiduguri, Nigeria
|Date of Web Publication||6-Sep-2014|
Dr. Ibrahim D Gezawa
Department of Medicine, Bayero University/Aminu Kano Teaching Hospital, Kano
Source of Support: None, Conflict of Interest: None
Background: Hypertension is the greatest preventable cause of death one of the most important modifiable risk factors for cardiovascular diseases. There is paucity of studies on the relationship between obesity and hypertension in northern Nigeria. Objective: To determine the prevalence of hypertension and its relationship with indices of obesity in Maiduguri, northeastern Nigeria. Materials and Methods: We recruited 1700 consenting adults aged 15-70 years using a multistage random sampling technique. Data on socio-demographic characteristics were obtained using a pretested questionnaire. Physical measurements for anthropometric indices and blood pressure (BP) were carried out using standard procedures. Hypertension was defined as systolic BP ≥ 140mmHg and/or diastolic BP ≥ 90mmHg. Multiple logistic regressions were fitted and odds ratios with 95% confidence intervals were calculated to identify associated factors. Results: Of the 1700 subjects recruited, 1650 responde, d yielding a response rate of 97%. The overall prevalence of hypertension was 32.3%, with a higher prevalence among women than men (46.1% vs. 34.5%, P < 0.05). Obesity was found in 15.9% of the study subjects. The prevalence of obesity was higher among women (20.7%) than men (13.6%). All the obesity indices correlated significantly with both SBP and DBP. Age ≥ 40 years, BMI and waist circumference in men were significantly associated with hypertension. Conclusion: The prevalence of hypertension in our study is high, particularly among women. Increasing age (>40 years), BMI and WC were found to be independently associated with hypertension. There is need for further studies to determine the role of lifestyle modification in reducing the burden of hypertension in our environment.
Keywords: Blood pressure, hypertension, Maiduguri, obesity, prevalence
|How to cite this article:|
Gezawa ID, Musa BM, Mijinyawa MS, Talle MA, Shehu YM, Uloko AE, Watila M M, Musa B M. Prevalence of hypertension and its relationship with indices of obesity in Maiduguri, Northeastern Nigeria. Niger J Basic Clin Sci 2014;11:67-71
|How to cite this URL:|
Gezawa ID, Musa BM, Mijinyawa MS, Talle MA, Shehu YM, Uloko AE, Watila M M, Musa B M. Prevalence of hypertension and its relationship with indices of obesity in Maiduguri, Northeastern Nigeria. Niger J Basic Clin Sci [serial online] 2014 [cited 2019 May 23];11:67-71. Available from: http://www.njbcs.net/text.asp?2014/11/2/67/140307
| Introduction|| |
Hypertension represents the single greatest preventable cause of death in humans and one of the most important modifiable risk factors for cardiovascular diseases.  Analysis of the global burden of hypertension revealed that over 25% of the world's adult population had hypertension in 2000, and the proportion is expected to increase to 29% by 2025.  Limited data on the trends of the prevalence of hypertension suggest that it has increased in developing countries in recent years, while it remained stable or decreased in developed countries. 
The developing countries are also witnessing an alarming increase in the prevalence of overweight and obesity.  Obesity has been associated with several non-communicable diseases such as hypertension, diabetes and lipid disorders as well as with increased morbidity and mortality among adults.  Both obesity and hypertension constitute important components of the metabolic syndrome, raising the possibility of insulin resistance as the link between the two disorders.
Several epidemiological studies in the past have consistently reported significant association between obesity indices and blood pressure (BP) levels. ,, Most of these previous studies have found body mass index (BMI) to be the best predictor of hypertension among their subjects. In Nigeria, the few population based studies on the relationship between obesity indices and BP were conducted in the southwestern part of the country. , The aim of our study was to determine the prevalence of hypertension and its relationship with obesity indices in an urban population of northeastern Nigeria.
| Materials and Methods|| |
The study was conducted in Maiduguri, the capital of Borno State in northeastern Nigeria. Subjects were selected using a multistage sampling technique. At stage one, Maiduguri Metropolitan Council (MMC) was picked (by lot casting) from the two existing local governments in Maiduguri. At stage two, Gwange 1 ward was selected by simple random sampling from the 22 wards in MMC. The selection was done using simple balloting. At stage three, household enumeration to identify eligible residents was conducted. In all, 1700 subjects from 340 households selected systematically (every second household based on calculated sampling fraction) were identified and were invited to participate in the study. Those excluded include pregnant women, subjects that cannot stand or are wheelchair-bound and those that are unwell. Permission and cooperation for the study was obtained from the ward head of Gwange ward and consent sought individually from the participants before being enlisted. The ethics committee of the University of Maiduguri Teaching Hospital approved the study.
The survey was conducted twice weekly (Saturdays and Sundays) between July 2008 and January 2009. Subjects presented at the survey site between 0800 and 1200 hours. After registration, trained assistants carried out data collection from eligible subjects using a pre-tested questionnaire. Anthropometric variables were measured using calibrated instruments following standard guideline.  Locally fabricated Stadiometre was used to measure heights, while weight was measured using a bathroom scale (Soehnle-Waagen GmbH and Co.KG, Wilhelm-Soehnle-Straβe 2 D-7154 Murrhardt/Germany). A non-stretchable dressmaker's tape was used to measure waist and hip circumferences. Body mass index (BMI) was calculated by dividing the weight (kg) by the square of the height in metres (m 2 ). Individuals were categorised into four groups based on BMI: Underweight (<18.5), normal weight (18.5-24.9), overweight (25.5-29.9) and obese (>30).  Waist circumference (WC) was measured to the nearest 0.1 cm (with a non-stretchable dressmaker's tape) at a point mid-way between the margin of the lowest rib and the iliac crest. WC exceeding 102 cm in men and 88 cm in women were considered abnormal.  Hip circumference was measured at the horizontal level of maximum circumference around the buttocks (posteriorly) and the pubic symphysis (anteriorly) to the nearest 0.1 cm. Waist-to-hip ratio (WHR) was calculated by dividing the waist circumference (cm) by the hip circumference (cm). WHR > 0.9 in men and >0.85 in women were also considered abnormal.  Blood pressure (BP) in millimeter of mercury (mmHg) was measured to the nearest 2 mmHg, on the right arm with subjects seated quietly after five minutes of rest with the arm and back supported using a standard mercury sphygmomanometer with an appropriate sized arm cuff. Systolic BP (SBP) was recorded at Korotkoff phase 1, while diastolic BP (DBP) was recorded at phase 5. Two readings were recorded 3 minutes apart and the average taken as the mean blood pressure. Similar methodology was used in previous studies. , Hypertension was defined as SBP ≥ 140 mmHg or DBP ≥ 90 mmHg. 
Data were analysed using STATA, Version 6.0 (Stata Corp, College Station, Tex). Independent t-test was used to compare means. Pearson's correlation coefficients were used to determine the relationship between obesity indices and BP. Multivariate logistic regression analyses were performed and the odds ratios with 95% confidence intervals were calculated to determine the independent associations of the anthropometric indices and hypertension. P values 0.05 or less were considered statistically significant.
| Results|| |
Of the 1700 subjects approached for enrollment, 1650 responded, thereby yielding a response rate of 97%. The study sample consisted of 1114 (67.5%) males and 536 (32.5%) females. The mean (SD) age of the subjects was 36.2 (14.4) years [males 34.9 (14.3); females 39.1 (13.9); respectively, P < 0.001] with a range of 15-70 years. The general characteristics of the study subjects are shown in [Table 1]. Indices of obesity were observed to be higher in women, except WHR. The prevalence rates of overweight and obesity were 23.6% and 15.9%, respectively [22.2% and 13.6% in men, and 26.7% and 20.7% in women respectively, P < 0.001]. The mean (SD) values of SBP and DBP of the subjects were 131.3 (22.9) mmHg and 86.0 (25.7) mmHg respectively. Both SBP and DBP were higher in women than in men [135.3 (26.6) and 87.0 (14.8) against 129.4 (20.7) and 85.5 (29.5) respectively, P < 0.001]. A significant positive correlation was observed between the indices of obesity and both SBP and DBP [Table 2]. Hypertension was detected in 32.3% of the study subjects and was significantly higher (P < 0.001) in women (46.1%) than in men (25.7%). The mean (SD) BMI, WC and WHR were higher (P < 0.001) in hypertensive than normotensive subjects as shown in [Table 3]. Analysis of the prevalence of hypertension according to BMI categories [Table 4], showed a rising trend in hypertension rates across the BMI categories with significantly more women (70.2%) than men (39.7%) being hypertensive among obese subjects (P < 0.001). In univariate analysis, the identified predictors of hypertension were aged >40 years (OR 4.919, 95% CI 3.825-6.329, P < 0.001), WC in men (OR 4.478, 95% CI 3.229-6.211, P < 0.001) and WC in women (OR 3.136, 95% CI 2.526-3.893, P < 0.001), WHR in men (OR 2.292, 95% CI 1.857-2.829, P < 0.001) and WHR in women (OR 2.417, 95% CI 1.829-3.193, P < 0.001) and obesity (OR 1.962, 95% CI 1.625-2.369, P < 0.001). However, when all of these variables were entered into a multivariate logistic regression model, the independent predictors of hypertension were aged >40 years (OR 4.919, 95% CI 3.825-6.329, P < 0.001), WC in men (OR 1.792, 95% CI 1.152-2.786, P = 0.01) and obesity (OR 2.239, 95% CI 1.072-4.675, P = 0.032).
|Table 2: Correlation between obesity indices and cardiovascular parameters among the study subjects|
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|Table 3: Comparison of obesity indices of normotensive and hypertensive subjects|
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|Table 4: Distribution of study subjects according to BMI categories and prevalence of hypertension by gender|
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| Discussion|| |
Hypertension is among the leading causes of death globally. It increases risks of stroke, heart diseases, renal failure and other diseases. , Obesity indices have been recognised for estimating cardiovascular disease risk factors particularly due to their strong association with hypertension. , The overall prevalence of hypertension of 32.3% found in this study is similar to the 30.4% reported by Adedoyin et al. in southwestern Nigeria.  The observed prevalence of hypertension in our study is, however, higher than the 28.3% reported from a community-based survey in Ethiopia,  but lower than the 65% reported among Pakistanis.  Although genetic and racial factors may explain the difference between the latter study and ours, it is worth noting that our study population is undergoing both nutritional and epidemiological transition and unless drastic measures are taken the prevalence of hypertension is likely to continue to rise over the coming years. The higher prevalence of hypertension in women (46.1%) compared with men (25.7%) observed in this study contrasts with earlier reports from population-based surveys across Africa that showed a higher prevalence of hypertension in men. , Our finding is however in keeping with studies from Zimbabwe  and Morocco.  The higher prevalence of hypertension in women than in men has been referred to as reversed gender dichotomy. One explanation given for reversed gender dichotomy was higher indices of obesity and elevated level of insulin resistance in the women.  Indeed in this study, the mean values of all the obesity indices except WHR, were observed to be higher in women than in men. We have previously documented a positive and significant correlation between WC and BMI and measures of insulin resistance in our study population.  Indices of global (BMI) and central (WC, WHR) obesity in our study correlated significantly with both SBP and DBP, a finding similar to that of Sanya et al. in southwestern Nigeria.  The prevalence of overweight and obesity among our subjects was 23.6% and 15.9% respectively, with significantly higher prevalence among women compared with men (26.7% and 20.7% against 22.2% and 13.7%). When compared with reports from other studies in northern Nigeria, the prevalence of obesity in our study is higher than 13.1% reported by Bakari et al.  but lower than the 21% reported by Wahab et al.  among their subjects. We also found the prevalence of hypertension in this study to be higher among obese women than in obese men. Multivariate logistic regression analysis revealed age >40 years, obesity (BMI ≥ 30 kg/m 2 ) and WC in men to be significantly associated with hypertension. This is similar to the findings of Shanthirani et al.  who reported age and BMI to be strong predictors of hypertension and concurs with the report by Sakurai et al.  among the Japanese. The independent effect of WC as a predictor of hypertension as demonstrated in this study, confirms previous assertions that WC may be a better predictor of hypertension than either BMI or WHR.  It is possible that the higher proportion of men compared with women in this study may have contributed to this observation since visceral fat is known to predominate in men as opposed to subcutaneous fat in women. There is nevertheless, the need for studies, preferably prospective in design to explore further the relationship between increased WC and hypertension in our setting.
The limitations of our study include its cross-sectional design, which hinders the establishment of precedence in time between variables investigated and the outcome of interest. The strength of our study includes the fact that it is a population-based study, in which trained interviewers carried out data collection. This study also provides baseline data on which future studies can build upon because, to the best of our knowledge, this is the first study on the prevalence of hypertension and its relationship with indices of obesity in our setting.
| Conclusion|| |
The prevalence of hypertension in our study sample is high, particularly among women. Increasing age (>40 years), BMI and WC were found to be independently associated with hypertension among our subjects. There is need for further studies to determine the role of lifestyle modification in reducing the burden of hypertension in our environment.
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[Table 1], [Table 2], [Table 3], [Table 4]