Prevalence and Determinants of Masked Hypertension in Nigeria: The REMAH Study.

BACKGROUND: Estimating the burden of hypertension in Nigeria hitherto relied on clinic blood pressure (BP) measurement alone. This excludes individuals with masked hypertension (MH), i.e., normotensive clinic but hypertensive out-of-clinic BP. METHODS: In a nationally representative sample of adult Nigerians, we obtained clinic BP using auscultatory method and out-of-clinic BP by self-measured home BP with semi-automated oscillometric device. Clinic BP was average of 5 consecutive measurements and home BP was average of 3 days duplicate morning and evening readings. MH was clinic BP <140 mm Hg systolic and 90 mm Hg diastolic and home BP ≥135 mm Hg systolic and/or 85 mm Hg diastolic. RESULTS: Among 933 participants, the prevalence of sustained hypertension, MH, and white-coat hypertension was 28.3%, 7.9%, and 11.9%, respectively. Among subjects whose clinic BP were in the normotensive range (n = 558), the prevalence of MH was 13%; 12% among untreated and 27% among treated individuals. The mutually adjusted odds ratios of having MH among all participants with normotensive clinic BP were 1.33 (95% confidence interval, 1.10-1.60) for a 10-year higher age, 1.59 (1.09-2.40) for a 10 mm Hg increment in systolic clinic BP, and 1.16 (1.08-1.28) for a 10 mg/dl higher random blood glucose. The corresponding estimates in the untreated population were 1.24 (1.03-1.51), 1.56 (1.04-2.44), and 1.16 (1.08-1.29), respectively. CONCLUSIONS: MH is common in Nigeria and increasing age, clinic systolic BP, and random blood glucose are the risk factors.

Urinary sodium excretion and its association with blood pressure in Nigeria: A nationwide population survey.

Assessment of level of salt intake in a population is the first step toward planning strategies aimed at salt reduction. As a surrogate of salt intake, we measured a single 24-hour urine sodium (uNa) of free-living 2503 adults in a nationally representative sample of Nigerians drawn from 12 rural and urban communities; and evaluated the community-level association of uNa with blood pressure (BP). Overall, the median (interquartile range (IQR)) of uNa was 99 (105) mmol, ranging from 23.8 (32.4) in rural north-central to 172.8 (131.0) mmol in urban northwestern region. Daily uNa was significantly higher (p < .001) in men compared to women (107.1 vs 93.9 mmol); and urban compared to rural dwellers (114.9 vs 86.0mmol). About one-half of participants excreted uNa in excess of recommended daily maximum value (86mmol). In a model adjusted for age, sex, body mass index (BMI), level of education, place of residence, and use of antihypertensive medication; being a man (odds ratio, OR 1.69, 95% confidence Interval CI, 1.21-2.37, p = .002) and being < 60 years of age (OR 1.74, 95% CI 1.23-2.45, p = .002), were associated with excreting higher than recommended uNa. In a fully adjusted model of the community-level analysis, urinary sodium, potassium, and sodium-to-potassium ratio each showed no significant independent association with both systolic and diastolic BPs. Among adult Nigerians, the median daily uNa excretion was 99 mmol and it had no significant association with blood pressure indices.

Prevalence, Awareness, Treatment and Control of Hypertension in Nigeria: Data from a Nationwide Survey 2017.

Background: Previous studies that evaluated the prevalence, awareness and treatment of hypertension in Nigeria were either localized to some specific regions of the country or non-standardized thereby making evaluation of trend in hypertension care difficult. Methods: We used the World Health Organization (WHO) STEPwise approach to chronic disease risk factor surveillance to evaluate in a nationally representative sample of 4192 adult Nigerians selected from a rural and an urban community in one state in each of the six geo-political zones of the country. Results: The overall age-standardized prevalence of hypertension was 38.1% and this varied across the geo-political zones as follows: North-Central, 20.9%; North-East, 27.5%; North-West, 26.8%; South-East, 52.8%; South-South, 44.6%; and South-West, 42.1%. Prevalence rate did not differ significantly (p > 0.05) according to place of residence; 39.2% versus 37.5 %; urban vs rural. Prevalence of hypertension increased from 6.8% among subjects less than 30 years to 63.0% among those aged 70 years and above. Awareness was better (62.2% vs. 56.6%; P = 0.0272); treatment rate significantly higher (40.9 % vs. 30.8%; P < 0.0001) and control similar (14 vs. 10.8%) among urban compared to rural residents. Women were more aware of (63.3% vs. 52.8%; P < 0.0001); had similar (P > 0.05) treatment (36.7 vs. 34.3%) and control (33.9% vs. 35.5%) rates of hypertension compared to men. Conclusion: Our results suggest a large burden of hypertension in Nigeria and a closing up of the rural-urban gap previously reported. This calls for a change in public health policies anchored on a primary health care system to address the emerging disease burden occasioned by hypertension.

Office and Home Blood Pressures as Determinants of Electrocardiographic Left Ventricular Hypertrophy Among Black Nigerians Compared With White Flemish.

BACKGROUND: The association of electrocardiographic left ventricular hypertrophy (ECG-LVH) with blood pressure (BP) in Blacks living in sub-Saharan Africa remains poorly documented. METHODS: In 225 Black Nigerians and 729 White Flemish, we analyzed QRS voltages and voltage-duration products and 12 criteria diagnostic of ECG-LVH in relation to office BP (mean of 5 consecutive readings) and home BP (duplicate morning and evening readings averaged over 1 week). RESULTS: In multivariable analyses, QRS voltage and voltage-duration indexes were generally higher in Blacks than Whites. By using any of 12 criteria, ECG-LVH was more prevalent among Black than White men (54.4% vs. 36.0%) with no ethnic difference among women (17.1%). Precordial voltages and voltage-duration products increased with office and home systolic BP (SBP), and increases were up to 3-fold steeper in Blacks. In Blacks vs. Whites, increases in the Sokolow-Lyon voltage associated with a 10-mm Hg higher SBP were 0.18 mV (95% confidence interval [CI], 0.09-0.26) vs. 0.06 mV (0.02-0.09) and 0.17 mV (0.07-0.28) vs. 0.11 mV (CI, 0.07-0.15) for office and home BP, respectively, with a significant ethnic gradient (P < 0.05). The risk of ECG-LVH increased more with office and home BP in Blacks than Whites. CONCLUSIONS: Associations of ECG voltages and voltage-duration products and risk of ECG-LVH with BP are steeper in Black Nigerians compared with a White reference population. In resource-poor settings of sub-Saharan Africa, the ECG in combination with office and home BP is an essential instrument in risk stratification across the entire BP range.

Prevalence and Determinants of Masked Hypertension Among Black Nigerians Compared With a Reference Population.

Hitherto, diagnosis of hypertension in sub-Saharan Africa was largely based on conventional office blood pressure (BP). Data on the prevalence of masked hypertension (MH) in this region is scarce. Among individuals with normal office BP (<140/90 mm Hg), we compared the prevalence and determinants of MH diagnosed with self-monitored home blood pressure (≥135/85 mm Hg) among 293 Nigerians with a reference population consisting of 3615 subjects enrolled in the International Database on Home Blood Pressure in Relation to Cardiovascular Outcomes. In the reference population, the prevalence of MH was 14.6% overall and 11.1% and 39.6% in untreated and treated participants, respectively. Among Nigerians, the prevalence standardized to the sex and age distribution of the reference population was similar with rates of 14.4%, 8.6%, and 34.6%, respectively. The mutually adjusted odds ratios of having MH in Nigerians were 2.34 (95% confidence interval, 1.39-3.94) for a 10-year higher age, 1.92 (1.11-3.31) and 1.70 (1.14-2.53) for 10- or 5-mm Hg increments in systolic or diastolic office BP, and 3.05 (1.08-8.55) for being on antihypertensive therapy. The corresponding estimates in the reference population were similar with odds ratios of 1.80 (1.62-2.01), 1.64 (1.45-1.87), 1.13 (1.05-1.22), and 2.84 (2.21-3.64), respectively. In conclusion, MH is as common in Nigerians as in other populations with older age and higher levels of office BP being major risk factors. A significant proportion of true hypertensive subjects therefore remains undetected based on office BP, which is particularly relevant in sub-Saharan Africa, where hypertension is now a major cause of death.

Nigerian Population Research on Environment, Gene and Health (NIPREGH) - objectives and protocol.

Sub-Saharan Africa is currently undergoing an epidemiological transition from a disease burden largely attributable to communicable diseases to that resulting from a combination of both communicable and chronic non-communicable diseases. Data on chronic disease incidence, lifestyle, environmental and genetic risk factors are sparse in this region. This report aimed at providing relevant information in respect to risk factors that increase blood pressure and lead to development of intermediate cardiovascular phenotypes. We presented the rationale, objectives and key methodological features of the Nigerian Population Research on Environment, Gene and Health (NIPREGH) study. The challenges encountered in carrying out population study in this part of the world and the approaches at surmounting them were also presented. The preliminary data as at 20 November 2013 showed that out of the 205 individuals invited starting from early April 2013, 160 (72 women) consented and were enrolled; giving a response rate of 78%. Participants' age ranged from 18 to 80 years, with a mean (SD) of 39.8 (12.4) years and they were of 34 different ethnic groups spread over 24 states out of the 36 states that constitute Nigeria. The mean (SD) of office and home blood pressures were 113.0 (15.2) mm Hg systolic, 73.5 (12.5) mm Hg diastolic and 117.3 (15.0) mm Hg systolic, and 76.0 (9.6) mm Hg diastolic, respectively. Forty-three (26.8%) participants were hypertensive and 8 (5.0%) were diabetic. In addition to having the unique potential of recruiting a cohort that is a true representative of the entire Nigerian population, NIPREGH is feasible and the objectives realisable.

Quality of blood pressure phenotype in the Nigerian Population Research on Environment Gene and Health.

OBJECTIVE: In the ongoing Nigerian Population Research on Environment Gene and Health (NIPREGH), we are applying standardized epidemiologic methods to determine cardiovascular phenotypes including blood pressure (BP) among adult Black Africans of Nigerian origin. We present the quality control of the conventionally measured BP. PARTICIPANTS AND METHODS: BP observers were trained for 1 month on BP measurement at commencement of the project and were retrained for 2 weeks 4 months later. The observers measured BP five times consecutively on participants according to the existing guidelines using a mercury sphygmomanometer. Five criteria - the percentage of identical readings, end digit preference, number preference, odd BP readings and expected progressive reduction from the first to the fifth reading - were used to assess the quality of BP phenotype. RESULTS: As of 20 November 2013, a total of 1600 (800 each of systolic and diastolic BP) readings obtained from 160 participants were available for analysis. A total of 175 (21.9%) systolic and 160 (20%) diastolic readings were identical. Three (0.002%) of the 1600 BP readings were odd and 433 (27.1%) ended on a 0 (expected 20%). Per month analysis of digit preference indicates that the observers had no significant preference for any digit for the fourth, fifth and sixth month of the study (P>0.05). Systolic BP decreased significantly from the first reading to the fifth reading (P for trend<0.05), whereas the diastolic BP showed a nonsignificant trend towards reduction (P for trend>0.05). CONCLUSION: Inclusion of the quality assurance procedures for BP measurement immediately from the commencement of NIPREGH and the repeated training for the BP observers yield a high quality BP phenotype.