Materials and methods

Study design and setting

A community-based cross-sectional study was conducted to assess the prevalence of hypertension and its associated risk factors among adults residing in rural areas of Gwalior district, Madhya Pradesh. The study was carried out in the rural field practice area attached to the Department of Community Medicine, Gajra Raja Medical College, Gwalior. Data were collected over a one-year period from May 1, 2023, to April 30, 2024, among permanent residents aged 18 years and above living in the selected rural communities of the district.

Sample size calculation

The sample size was calculated using the Cochran formula for prevalence studies:

\begin{document}n=\frac{4pq}{L^{2}}\end{document}

where n is the required sample size, p is the estimated prevalence (%), q = 100 - p, and L is the allowable error (absolute precision). Based on findings from a previous study conducted in a rural population [11], the prevalence of hypertension was assumed to be 25%; therefore, p = 25 and q = 75. The allowable error was taken as 20% of the estimated prevalence, corresponding to an absolute precision of 5%. The minimum calculated sample size was 300 participants. After accounting for a 20% non-response rate, the final sample size was increased to 360 participants.

Sampling technique

A multistage sampling technique was employed to select the study participants. In the first stage, Gwalior district, comprising four administrative blocks (Morar, Ghatigaon, Dabra, and Bhitarwar), was considered as the sampling frame. All four blocks were included in the study to ensure representation of the entire rural field practice area.

In the second stage, one village from each administrative block was selected using simple random sampling by the lottery method. Accordingly, Hastinapur, Barai, Jourasi, and Bela villages were selected from Morar, Ghatigaon, Dabra, and Bhitarwar blocks, respectively.

In the third stage, a list of households in each selected village was prepared with the assistance of local health workers. Forty-five households from each village were selected by systematic random sampling. Within each selected household, two eligible adults (preferably the head of the household and the spouse) aged 18 years or older were included. If more than two eligible adults were present, the participants were selected by simple random sampling. If an eligible individual was unavailable after two visits or declined participation, the next eligible household was selected to maintain the required sample size.

This sampling procedure resulted in the enrolment of 90 participants from each village, giving a total sample of 360 participants (Figure 1).

Figure 1: Multistage sampling technique used for the selection of study participants in rural Gwalior district, Madhya PradeshThe figure illustrates the multistage sampling procedure adopted for the study. Gwalior district was stratified into four blocks (Morar, Ghatigaon, Dabra, and Bhitarwar). One village was selected from each block (Hastinapur, Barai, Jourasi, and Bela, respectively). Forty-five households were selected by systematic random sampling from each village, and two eligible adults were selected from each household according to the study protocol, yielding 90 participants from each village and a total sample of 360 participants.

As all four administrative blocks of the study area were included and probability-based sampling methods were used at each stage, the risk of selection bias was minimized. However, the preferential inclusion of household heads and spouses may have introduced some selection bias, which has been acknowledged as a limitation of the study. Although multistage sampling was adopted, a design effect was not applied because the sampling units were selected from geographically distinct villages with similar population characteristics, and the study was designed as a descriptive community-based prevalence survey rather than a complex population survey.

Inclusion and exclusion criteria

Permanent residents of the selected rural areas of Gwalior district aged 18 years and above were eligible for inclusion in the study. Individuals who were seriously ill, unable to participate in the interview, or unavailable after two household visits were excluded from the study.

Data collection procedure

Data were collected from May 2023 to April 2024 using a pre-designed, semi-structured, interviewer-administered questionnaire (Appendices). The questionnaire was pre-tested in a rural population outside the study area to assess its clarity, feasibility, and completeness, and minor modifications were made before the final survey. It included information on sociodemographic characteristics, dietary habits, physical activity, tobacco and alcohol use, family history of hypertension, comorbid conditions, and anthropometric measurements.

Face-to-face interviews were conducted during household visits by the principal investigator only using paper-based questionnaires. Written informed consent was obtained from each participant before the interview. Blood pressure and anthropometric measurements were recorded according to standardized procedures, and completed questionnaires were checked daily for completeness and consistency to ensure data quality.

Anthropometric and blood pressure measurements

The sphygmomanometer and weighing scale were checked and calibrated periodically throughout the study according to standard procedures. Anthropometric measurements were taken following standard procedures. Height and weight were measured to calculate BMI. Waist circumference and waist-to-hip ratio (WHR) were also measured to assess central obesity.

Blood pressure was measured with a standard sphygmomanometer. Participants were seated comfortably and rested for at least five minutes before blood pressure measurement. Two readings were obtained at five-minute intervals, and the average value was used for analysis.

Blood pressure levels were classified according to the Joint National Committee (JNC) guidelines [12]. Individuals with systolic blood pressure (SBP) less than 120 mmHg and diastolic blood pressure (DBP) less than 80 mmHg were classified as normotensive. Pre-hypertension was defined as systolic blood pressure of 120-139 mmHg or diastolic blood pressure of 80-89 mmHg. Stage 1 hypertension was defined as systolic blood pressure of 140-159 mmHg or diastolic blood pressure of 90-99 mmHg, while stage 2 hypertension was defined as systolic blood pressure of 160 mmHg or higher or diastolic blood pressure of 100 mmHg or higher.

Operational definitions

Hypertension was defined as a systolic blood pressure of 140 mmHg or higher and/or a diastolic blood pressure of 90 mmHg or higher, or in previously diagnosed individuals receiving antihypertensive treatment [12]. Overweight and obesity were classified according to body mass index criteria using standard recommendations [13].

Statistical analysis

The collected data were entered into Microsoft Excel 2019 (Microsoft Corp., Redmond, WA) and analyzed using Jamovi version 2.6.44 (The Jamovi Project, Sydney, Australia). Descriptive statistics, including frequencies and percentages, were used to summarize the study findings. Associations between hypertension and selected risk factors were assessed using the chi-square test. A p-value of less than 0.05 was considered statistically significant.

Ethical considerations

The study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki, including respect for participants' autonomy, voluntary participation, informed consent, confidentiality, privacy, and the right to withdraw from the study at any stage without any adverse consequences. Ethical approval was obtained from the Institutional Ethics Committee of Gajra Raja Medical College, Gwalior, prior to the commencement of the study (approval number: 93/IEC-GRMC/2023).

Confidentiality and privacy of participant information were strictly maintained throughout the study. Personal identifiers were removed from the analytical dataset, and all study records were stored securely with access restricted to the research team. Interviews and blood pressure measurements were conducted in a private setting to ensure participant comfort, dignity, and confidentiality.

Handling of missing data

Data collection forms were reviewed daily to ensure completeness and consistency. Missing or unclear responses identified during field visits were verified immediately when feasible. Participants lacking information on key study variables, such as blood pressure measurements and major risk factor assessments, were excluded from the final analysis. The proportion of missing data was minimal and did not materially influence the study findings. Consequently, statistical imputation techniques were not applied, and analyses were conducted using only complete-case data.