Study setting

The study will be conducted in public health facilities of Bahir Dar City from September 15, 2025, to June 30, 2026. We anticipate having the study results by August 2026. Bahir Dar is the capital city of the Amhara regional state and has a population of more than 750,991 residents [17]. There are three public hospitals and six health centers in the city. Based on a minimum of 5 patients/ month recruitment potential criteria, three hospitals and four health centers providing NCD care have been selected.

Hypertensive patients in the study health facilities are managed according to the Ethiopian National Noncommunicable Diseases Management Protocol [16]. According to this protocol, all adults visiting health facilities have their blood pressure measured as part of vital signs. The diagnosis of hypertension is confirmed by trained nurses with a BSc degree or Public Health Officers in health centres or by General Practitioners (medical doctors) in hospitals. In a health care facility with electricity or regular access to batteries, the Ministry of Health-Ethiopia recommends using an automated, validated blood pressure device with a digital reading to measure blood pressure. If the health care facility has no electricity or batteries, a manual (Aneroid or Mercury) BP apparatus can be used by auscultation with a stethoscope.

Once the patients’ diagnosis is confirmed, they will be linked to a follow-up clinic typically staffed with general practitioners, nurses, or public health officers. Under normal circumstances, patients attend the clinic monthly to refill their medications, adjust medication, and achieve the target blood pressure.

Study design

The study will employ a prospective cohort design in which adults with newly diagnosed hypertension will be recruited at the time of enrolment to care and followed for 6 months. Data will be collected at three time points: baseline, 3 months, and 6 months. The study flow is clarified more in the study framework (Fig 1).

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Fig 1. study framework adapted from Ambaw and colleagues [18].

HTN = Hypertension; BP = blood pressure; QoL = quality of life; PSS = perceived social support.

https://doi.org/10.1371/journal.pone.0343829.g001

Recruitment and data collection

The health professionals running the NCD clinic at each site will identify the study participants who meet the inclusion criteria consecutively until a total of 485 participants is reached, and link them to experienced and trained data collectors, who are BSc degree holders in health. The health professionals in the NCD clinics will also play a role in helping the data collectors review patients’ charts for hypertension treatment outcomes and comorbid illnesses. The data collectors will provide the patient with information about the study and seek their informed consent. They will enrol patients who consent and arrange appointment dates for the subsequent interviews, and carry out interviews at the health institutes.

Eligibility criteria

Sample size determination

The sample size has been calculated using the “Cohort or Cross-sectional study” sub-menu of Epi Info version 7.2. 1 (https://www.cdc.gov/epiinfo/index.html) with a 95% confidence level and 80% power. We used the proportion of ‘ unsuccessful treatment outcomes’ in hypertension patients with baseline depression and without baseline depression to be 12.9% and 3.4% respectively, from a proxy in TB patients [19]. The ratio of 3:1 for unexposed to exposed, along with a 20% contingency for loss to follow-up, was considered. The required sample size is 404. The final target sample size, including the contingency, is 485 (363 without depression and 122 with depression).

Sampling technique

We will use consecutive sampling, where participants will be included in the study as long as they fulfil the inclusion and exclusion criteria until the targeted sample size is reached. Consecutive sampling technique is a common practice in healthcare research, particularly when the study population is infinite. It is claimed to be reasonably representative when: a) multiple sites are included, b) all eligible participants are invited to participate, and c) the data collection period is long [20]. The participants of this study will be recruited from seven centres over ten months

Variables and measurement

Independent variables

Independent variables will be measured using previously successfully applied tools.

1. Socio-demographic variables: Data will be collected on age, sex, marital status, level of education, religion, household income, occupation, and place of residence (urban versus rural).
2. Pain: Pain will be measured using a visual analogue scale, where values will be scored from 0 (absence of symptom) to 10 (worst level of symptom severity), as perceived by the respondent for that week. The responses will be categorised as follows: no symptom (0), mild (12–3), moderate (4–6), and severe (7–10) to indicate intensity [31].
3. Substance use: Alcohol, tobacco products, and khat use will be assessed using the WHO Alcohol, Smoking and Substance Involvement Screening Test, version 3.1 (ASSIST 3.1) [32]. ASSIST is a valid and reliable scale for use in cross-cultural settings, to assess multiple drug use, to detect different levels of drug use, and is applicable in primary care settings [33–36]. In this study, the various types of tobacco and khat will be considered similar. Similarly, the local alcoholic drinks ‘tella,’ ‘tej,’ and ‘araki’ will be considered standard drinks. The alcoholic percentages per volume for these Ethiopian traditional alcoholic beverages are 3.84 to 6.48, 8.94 to 13.16 and 33.95 to 39.9% respectively [37].
4. Co-morbid illness: Data on the presence of chronic illnesses other than hypertension will be collected by asking the respondents if they have been diagnosed with any chronic illnesses.
5. Perceived social support (PSS) is the expectation that support will be provided from one’s social network [38]. PSS will be measured using the three-item Oslo Scale of Perceived Social Support (Oslo 3) [39] at continuous levels, with higher scores showing better perceived social support.
6. Severity of hypertension: Severity of hypertension will be categorised into five grades according to the national guideline as Grade-1, Grade-2, Grade-3, ‘Hypertension Emergency’, and ‘Hypertension Urgency’.

Method of analysis

Descriptive statistics will be used to summarise both dependent and independent variables. The prevalence of depression among patients at baseline will be determined by calculating the proportion of patients scoring 10 or more on the PHQ-9 scale. Factors associated with depression at baseline will be analysed using Poisson regression with a robust variance estimator, a recommended approach for analysing prevalence ratios in cross-sectional studies with binary outcomes where the outcome is common [40,41,42]. The proportion of patients with hypertension who scored below 10 on PHQ-9 at baseline but had scores of 10 or above at the end of the third month will be calculated to determine the incidence (risk) of depression at 3 months. This will be repeated at 6 months. To examine the course of co-morbid depression, the percentage of participants with over 50% reduction in PHQ-9 scores will be calculated at three and six months. The effect size of the change from baseline to endpoint will be measured using Cohen’s d with Hedges’ correction after checking correlation coefficients to be around 0.5 and standard deviations to become equal, as recommended by Lakens [43]. To identify the predictors of reduction or change in PHQ-9 scores over time, multilevel mixed-effects linear regression with maximum likelihood estimation will be employed. Repeated measurements will be considered nested within individual participants, and individuals will be nested within health institutions. Assessment times will be coded as 0, 3, and 6 for baseline, 3-month, and 6-month assessments, respectively.

Blood pressure control status at three and six months will be classified as controlled or not controlled. To evaluate the impact of baseline depression on hypertension control, risk ratios between participants with and without baseline depression will be calculated using Poisson working model with a robust variance estimator. Follow-up time will be incorporated as a weighting variable in the analysis of each outcome.

To examine the impact of co-morbid depression on disability and quality of life, an independent samples t-test will be used. To assess changes in health-related quality of life and disability scores from the time of diagnosis to the end of follow-up, a multilevel mixed-effects generalised linear model will be fitted, considering the three measurement times (baseline, three months, and six months) as nested within individuals, and individuals nested within health institutions. Time will be centred at baseline, with baseline coded as zero, the third month as 3, and six months as 6.

All our inferential analyses, including independent variables in the multivariable analysis, will be based on a) their theoretical importance and b) the adequacy of the number of cell participants for each category. P-values less than 0.05 will be considered statistically significant.

Ethical considerations

Ethical approval was obtained from the Institutional Review Board (IRB) of the College of Medicine and Health Sciences, Bahir Dar University, on April 2, 2025 (Protocol number: 3095/2025). Written informed consent will be obtained from participants. A data collector will read the information sheet and the consent form for participants who cannot read or write; they will then sign in the presence of a witness. All participants who endorse the suicide item or score ten or above on PHQ-9 will be referred to staff at the health institutions for further psychiatric evaluation. Participants will be free to withdraw from the study at any time.