High burden of hypertension across the age groups among residents of Gondar city in Ethiopia: a population based cross sectional study

This study was conducted in Gondar town, in the North-west part of Ethiopia located 750 Km from the capital Addis Ababa. It is one of the largest cities in the country with a population of 358, 257. A community based cross sectional study design was implemented. All individuals of age greater than or equal to 18 years who reside in Gondar city for at least six months were included. The sample size for the study was determined by assuming 50% prevalence with a 95% confidence interval and 5% margin of error. We also consider a 5% non-response rate. After having the minimum sample size stratification of the sample for age and sex was done (four age categories multiplied by two (for male and female), accordingly, the calculated sample size was 3227 individuals.

A multistage cluster random sampling method was used. At first, four administrative kebeles (the smallest administrative units in Ethiopia which consists of at least 500 families) were randomly selected from the 12 administrative kebeles using simple random sampling after obtaining the list from the Gondar city administration. Households were selected within each administrative kebeles using the systematic random sampling technique. Finally, eligible adult from each group until the required sample was selected from each household using simple random sampling. In cases where there were more than one eligible individual in the selected household, a lottery method was used to pick one (The Kish method from WHO step instrument of random sampling method was used for selecting one individual from each household).

All the individuals were given an identification number and a household number by the data supervisor.

Data were collected by interviewing eligible subjects using a structured questionnaire. House-to-house data collection was performed by trained nurses. The field study team was composed of enumerators, laboratory technicians, Health extension nurses, and supervisors. All were trained by the principal investigators for two days on the study procedures. To ensure the quality of the interview the supervisors checks 5 to 10% of daily collected the questioners.

WHO’s STEP-wise approach was used only in Gondar which is one of the largest towns in the country. We implemented the WHO and International Diabetic Association (IDA)criterion to classify hypertension with systolic blood pressure (SBP) of ≥140 mmHg and /or a diastolic blood pressure (DBP) ≥ 90 mmHg or known hypertensive patients on treatment. Isolated systolic hypertension (ISH) was defined as having a systolic blood pressure ≥ 140 mmHg and diastolic blood pressure < 90 mmHg and Isolated diastolic hypertension (IDH) was defined as having a systolic blood pressure < 140 mmHg and diastolic blood pressure ≥ 90 mmHg). Blood pressure (BP) was measured using a digital measuring device with participants sitting after resting for at least five minutes. Three BP measurements were taken with at least three-minute intervals between the consecutive measurements. The mean systolic and diastolic BP from the second and third measurements was considered for analyses [16]. Finally, biochemical tests (fasting blood glucose (FBG), triglyceride, LDL, HDL and total cholesterol test) were carried out [17]. Blood samples were collected from each participant by a trained laboratory technician following aseptic techniques. The blood samples were taken to the hospital laboratory for chemistry analyses. Biochemical tests were carried out using 902 Automatic Analyzer with following a minimum of 8 h fasting period, early in the morning before participants took their breakfast. [18, 19]. We used a ‘yes’ and ‘no’ question to extract history of smoking and alcohol consumption.

The WHO’s STEP-wise instrument approach was employed in the questions that assessed hypertension risk factors [16]. Anthropometric measurements were taken using standardized techniques and calibrated equipment. Subjects were weighed to the nearest 0.1 kg in light indoor clothing and bare feet or with stockings. Height was measured using a stadiometer; participants stood in erect posture without shoes, and the results were recorded to the nearest 0. 5 cm. Measures were taken two times, and the average was considered in the analysis. BMI was used to define underweight (BMI < 18. 4), normal (18. 5 ≤ BMI < 24. 0), overweight (25. 0 ≤ BMI < 29. 0), and obese (BMI ≥ 30) adults [17].

Data entry procedures were done using the EPI Info version 3.5.3 statistical software. A stratified analysis was also performed to look at age, residence and sex specific proportion. The prevalence estimation was made along with a 95% confidence interval (CI). The results were considered statistically significant at P ≤ 0. 05. Logistic regression was applied to identify the associated factors with hypertension. To fit the multivariate analysis, independent variables were selected based on the conceptual framework and prior evidences in the literature and their effect in the current analysis using bivariate analyses; a cut of point p-value <0.20 was included. The independent variables, like socio-demographic factors and health related life-style characteristics of the study population were computed in the multivariable logistic regression analysis. Statistical analysis was performed using STATA version 14 software.

The protocol was approved by the Institutional Review Board (IRB) of the University of Gondar. In addition, a written permission was obtained from the respective local administration and hospital director. Participants were recruited voluntarily after obtaining full information about the research and signed a written consent agreement. They were informed of their rights to withdraw from the study at any stage. For the sake of privacy and confidentiality no personal identifiers such as names were collected.

The mean (±SD) systolic and diastolic blood pressures were 125.3 (±19. 8) mmHg and 78.5 (±11. 4) mmHg, respectively. SBP was found to increase progressively with age in both sexes; whereas, the DBP was found to progressively increase only up to the age of 45–54 years of age and stabilizes thereafter in both sexes (Fig. 1). The sex specific mean (±SD) of SBP and DBP were 127 (±18. 4) and 79.9 (±11. 6) in males and 123.7 (±20. 7) and 77.3 (±11) in females, correspondingly.

The overall prevalence of HTN was 27. 4% [95% CI: 25. 8%-28. 9%]. The prevalence consistently increased from 9.5% in the 18–25 year group to 46.3% in those above 65 years (p-value <0. 001). The prevalence in participants above 35 years was 36. 1%. Overall, hypertension was more common in males (29%) than females (25. 4%) (p-value = 0. 05). This difference was maintained up to the age of 65 years. However, in participants above 65 years hypertension was more common in females (48. 4%) than males (44. 3%) as illustrated in Fig. 2.

The overall prevalence of ISH was 9. 4% [95%CI: 8. 4%-10. 5%]. It progressively increased with increasing age, from 2.7% in participants of age 18––24 years to 23.4% in those above 65 years. Figure 3 shows that the sex specific prevalence was consistently higher in males than females in participants of age 25–65 years. But, above the age of 65 years more females (26. 1%) than males (20. 5%) had ISH.

The overall prevalence of IDH was 5. 5% [95%CI: 4. 7%-6. 4%]. Figure 4 shows that it peaked in the 25–34 years group with a prevalence of 7%. It was higher in males compared to females across all age groups.

Based on the participants recall only 1443 (47. 2%) of the study participants, 43. 3% among males and 50. 5% among females, had history of ever getting a blood pressure measurement in their life time regardless of the purpose of measurement. Only 229 (7. 1%) of the participants were already diagnosed with hypertension and were taking anti-hypertensive treatment. Of the patients who were on antihypertensive treatment 128 (55. 9%) had controlled hypertension at the time of the study (BP < 140/90 mmHg). Out of the 876 hypertensive cases in the study, 72.6% were not aware of their hypertension status until they were diagnosed during this survey.

The factors significantly associated with hypertension among the non-modifiable risk factors were age, sex, place of birth and marital status. The male gender compared to females was independently associated with hypertension (AOR = 1. 42; 95% CI: 1. 18, 1. 72). Increasing age was strongly associated with hypertension. The odds of hypertension was more than 5 times higher among participants who were older than 65 years compared to those in the age group of 18–24 years (AOR = 5. 56; 95% CI: 3. 71, 8. 35). Individuals who were born and raised in the urban area also exhibited a 33% higher odds of having hypertension compared to those born and raised in rural areas, (AOR = 1. 33; 95% CI, 1. 10, 1. 56). Being widowed (AOR = 1. 87; 95%CI: 1. 27, 2. 75) and being separated (AOR = 1. 87; 95% CI: 1. 27, 2. 75) were found to be independently associated with hypertension compared to having a single marital status.

Among the conventional modifiable risk factors, obesity (AOR = 2. 62; 95% CI: 1. 70, 4. 03) and overweight (AOR = 2. 29, 95% CI: 1. 64, 3. 19) were found to be independently associated with hypertension compared to underweight. Compared to being underweight, even having a normal BMI was associated with higher occurrence hypertension (AOR = 1. 51; 95%CI: 1. 12, 2. 03). Compared to individuals who have never used alcohol in the preceding twelve months, participants with a history of daily alcohol use in the preceding year had independent association with hypertension (AOR = 1. 51; 95%CI: 1. 02, 2. 23) (Table 3).