Study setting, design, and period
A community-based cross-sectional study was conducted from April 1 to 30, 2021, in Mizan Aman town, the capital and administrative center of Bench Sheko Zone in the Southwestern Nations Nationalities Peoples Region (SWNNPR). Based on the report from the sub-city administration office, the total population of Mizan Aman town is estimated to be 54, 951, of the total 26,925 of them are male and the rest 28,026 are female. Among the total 54, 951 population residing in the town, about 60.3% are estimated to be above 18 years old.
Sampling techniques and sample size
A multistage sampling method was employed to recruit study participants. First, three kebles (the smallest administration localities), (Addis Ketema, Edget, and Kometa Keble) were selected using simple random sampling out of the five kebles in the town. Secondly, the sample size determined, the households, was allocated proportionally to each of the selected keble and the households were selected within each keble using the computer-generated random sampling technique (Figure1). The sampling frame was prepared using the list of households from the family folder available at health posts. Finally, one adult whose age was 18 years and above was selected from each household using a simple random sampling technique if there were two or more eligible adults living in the same household.
Inclusion: All adults aged 18 years and above who reside in the study area during the study period.
Exclusion: Medically confirmed cases of HTN, pregnant women, and women at ministration period have been excluded from the study.
The sample size was calculated to get the maximum representative sample size and to determine each specific objective separately.
For the first specific objective, the sample size was calculated using single population proportion formula based on the following assumptions. The prevalence of undiagnosed HTN (p=12.3%) was taken from a previous similar study (7), 95% level of confidence, 3% margining of error (d), a design effect of 1.5 and 10% for a possible non-response rate was taken and the formula applied as shown below.
For the second specific objective, the sample size was calculated by using EPI INFO stat calc for population proportions to estimate a sufficient sample. Factors associated with HTN and respective parameters are obtained from a study conducted in different parts of Ethiopia. Finally, the prevalence of gender (being male ) to be 16.13% with an AOR of 2.5 at (1.2,5.2)of CI was taken from a study conducted in Hawela Tula Sub-City, Hawassa, Southern Ethiopia (7), and taking 95% confidence interval, 80% power, 1.5 a design effect and, 10% of non-response rate were used to calculate sample size for each associated factors.
Among the given two computed alternatives, the first computed alternative yielded the maximum number than the one produced by the double population proportion formula and hence, the final sample size for this study was found to be 759 subjects.
Data Collection
A structured, and pretested questionnaire adapted from the WHO STEPS wise approach for surveillance of NCDs in developing countries was used to interview the participants (17).
Data collection was done sequentially in a two-step process:
Step 1: Interview-based questionnaire on selected major health risk behaviors including smoking, alcohol consumption, poor fruit and vegetable consumption, and physical inactivity.
Step 2: Physical measures of health risks such as height, weight, blood pressure, body mass, and waist and hip circumference.
Anthropometric measurements were taken based on the WHO guidelines, as specified in the Food and Nutrition Technical Assistance (FANTA) anthropometry manual (18). Blood pressure was measured in a sitting position with a supported back, and digital automatic blood pressure (BP) device was used to measure the BP of the participants. The participants were taking rest for at least 5 min before measurement. Three measurements of BP on a single visit were taken at least one minute apart, and this survey considered the last two measures of BP levels and used their mean to detect HTN. At least two visits were made for those study participants whose BP was elevated at the first contact. According to the WHO guideline, a participant with systolic blood pressure (SBP) ≥140mmHg or diastolic blood pressure (DBP) ≥90mmHg will be diagnosed as a HTN case (19).
Data quality assurance
Data were collected by two senior nurses under one supervisor following the training given on interviewing techniques, anthropometric measurements, and handling of data collection instruments for one day. The Questionnaire was prepared in English, then translates into Amharic, and then retranslated back to English to check its consistency. A pre-test was done on 5% of the sample out of the study area and then appropriate revision on the tool was done. Double-entry of the data to epidata software for data verification was also performed.
Data analysis
Data analysis was done by SPSS for windows version 25 and the descriptive analysis was undertaken and the result was presented using frequency tables, graphs, and descriptive statistical summaries. The undiagnosed HTN status has dichotomized response of yes and no and hence bivariable analysis was performed using binary logistic regression to identify candidate variables for the multivariable logistic regression model to identify explanatory variables associated with the outcome variable. Then those variables with a p-value <0.25 were included in multivariable logistic regressions for adjustment of confounding factors. Odds ratios (OR) with 95% confidence intervals were calculated to measure the strength of association and the p-value < 0.05 was considered statistically significant. The Hosmer-Lemeshow test was used to assess the fitness of the model (chi-square 3.9 with a p-value of 0.9).
Operational definition
Standard operational definitions were adapted for key variables to maintain consistency and uniformity of the information.
Undiagnosed HTN: adults (aged 18 years and above) will be considered undiagnosed for HTN if, at the time of the survey, he or she was diagnosed as hypertensive (SBP ≥140mmHg or DBP ≥90mmHg) but never took any prescribed antihypertensive medicine to lower or control blood pressure and was never been told by a health professional that they have HTN before this study (19).
Harmful use of alcohol: alcohol consumption of more than 14 units/week for men and more than 8 units/week for women in the last 12 months before the survey. Its calculation is then: Unit of alcohol = vol (in ml) X % alcohol/ 1000 and for different local alcoholic beverages then was: Tella (4%), Tej (10%) and arake (40-45%) alcohol content, (as Glass 250ml and bottle as 330ml) (20).
Low consumption of fruits and vegetables: Fewer than 5 servings (<400gm) of fruit and, or vegetables per day in that 1 serving is defined as one orange/apple/banana or three tablespoons of cooked vegetables (17).
A current smoker: an adult who has smoked 100 cigarettes in his or her lifetime and who currently smokes cigarettes. A previous smoker: an adult who has smoked at least 100 cigarettes in his or her lifetime but who had quitted smoking at the time of the interview. Never smoker: an adult who has never smoked, or who has smoked less than 100 cigarettes in his or her lifetime (21).
Physical activity; the subjects' physical activity was classified as high, moderate, and low
High physical activity is defined as a vigorous-intensity activity on at least 3 days achieving a minimum total physical activity of at least 1500 min/week OR 7 or more days of any combination of walking, moderate-intensity, or vigorous-intensity activities achieving a minimum total physical activity of at least 3000 min/week. Moderate physical activity is defined as 3 or more days of vigorous-intensity activity of at least 20 min per day OR 5 or more days of moderate-intensity activity and/or walking of at least 30 min per day OR 5 or more days of any combination of walking, moderate-intensity, or vigorous-intensity activities achieving a minimum total physical activity of at least 600 min/week. A low physical activity: not fulfilling the criteria for moderate and high physical activity (22).
A family history of HTN is considered if a person’s first-degree relative (a parent, a grandparent, or a sibling) had been diagnosed with HTN and/or was receiving drug therapy for HTN (23).