Prevalence and associated factors of pre‐hypertension and hypertension in Nepal: Analysis of the Nepal Demographic and Health Survey 2016

Abstract Objectives Hypertension is the leading risk factor for cardiovascular diseases and develops faster among pre‐hypertensive individuals. However, there is a lack of nationally representative studies that investigate the prevalence and determinants of these two conditions in many developing countries, including Nepal. This study investigates the prevalence and determinants of pre‐hypertension and hypertension in Nepal. Methods The present cross‐sectional analysis used data from the 2016 Nepal Demographic and Health Survey, collected from June 2016 to January 2017. After calculating the weighted prevalence (with 95% confidence interval [CI]), simple and multivariable analyses were performed to estimate odds ratios. Results A total of 14 857 individuals (6247 males and 8610 females) aged ≥15 years who had their blood pressure measured during the survey were included in this study. The prevalence for pre‐hypertension and hypertension were 26.0% (95% CI: 25.3‐26.3, n = 3856) and 19.5% (95% CI: 18.8‐20.2, n = 2899), respectively. The prevalence of both conditions was greater among males. In multivariable analyses, older age, male sex, higher body mass index, and residents of Provinces 4 and 5 had significantly increased odds of pre‐hypertension and hypertension (P < .05). Additionally, higher education level was found to be positively associated with hypertension. Conclusions The combined higher prevalence of pre‐hypertension and hypertension indicates that nearly half (45.5%) of the respondents are at a greater risk of cardiovascular and other non‐communicable diseases due to these two conditions. Older people, males, obese people, and individuals living in Provinces 4 and 5 require more awareness to control blood pressure levels.


| INTRODUCTION
Cardiovascular diseases are currently the leading causes of global deaths or disability-adjusted life years. [1][2][3] Hypertension is the principal risk factor for these diseases. [3][4][5] In addition, hypertension develops faster among pre-hypertensive persons or people with "high normal" blood pressure. 6 Over the last few decades, the prevalence of hypertension and other non-communicable diseases has increased at an alarming rate in developing countries due to the epidemiologic and demographic transitions in these countries. 2,3 Moreover, many developing countries are currently dealing with a problem that is also known as "twin" or "double" disease burden, where there is a concomitant higher incidence and prevalence of communicable and non-communicable diseases. [7][8][9] Although there have been continuous surveillance efforts to monitor incidence, trends, and prevalence of both communicable and non-communicable diseases in developed countries, limited information is available from developing countries. Most of the estimates in developing countries come from population-based or small-scale cross-sectional studies that are designed to estimate the overall burden and determinants of diseases. [1][2][3] Among the regions of the World Health Organization (WHO), hypertension and other cardiovascular disorders are increasing at a faster rate in South Asian countries compared with other regions. [7][8][9] Previous studies reported that prevalence and likelihood of pre-hypertension and hypertension vary according to several characteristics, including age, sex, body mass index (BMI), socioeconomic status, and place of residence. [10][11][12] These characteristics also affect awareness, treatment, and control of hypertension. 11,12 Nepal is a South Asian developing country with an estimated population of 29 million people, residing in a land mass of 147 181 square kilometers. This country is divided into seven provinces (Provinces 1-7), in three ecological zones: Mountain, Hill, and Terai. 13 Similar to many other countries, Nepal is facing the twin burden of diseases, and prevalence of hypertension is increasing at an alarming rate. 8,9 This country also lacks nationally representative data on the prevalence of hypertension. The Nepal Demographic and Health Survey 2016 (2016 NDHS) was one of the few surveys conducted in this country to estimate the overall prevalence of hypertension in Nepal. The prevalence of hypertension among males and females in that survey was 23% and 17%, respectively. In addition, the prevalence of pre-hypertension was 31% among males and 24% among females. 14 As the 2016 NDHS reported the prevalence after stratifying according to sex instead of demonstrating the overall prevalence of blood pressure levels according to background characteristics, this limits the understanding of the overall prevalence or burden of hypertension in this country.
Additionally, this survey also reported the point estimate of the prevalence of pre-hypertension or hypertension instead of the 95% confidence interval (CI); it is more important to report the CI to have a more precise estimate. 15 Studies that previously investigated prevalence and risk factors for hypertension in Nepal and other countries have found that these vary according to age, sex, body weight, race/ethnicity, place of residence, marital status, education level, socio-economic status, and concomitant diseases such as diabetes, dyslipidemia, or stress. 12,[16][17][18][19][20] Furthermore, due to similar restrictions for assessing prevalence from a nationally representative dataset, studies investigating the determinants of pre-hypertension or hypertension in Nepal are also limited by a shortage in recently collected data and the availability of only small-scale studies mainly conducted in a community or a particular region. 7,10,11,16,[21][22][23] Investigating prevalence and determinants from a nationally representative dataset is essential for designing and implementing a national evidence-based strategy to prevent and control pre-hypertension and hypertension, as well as minimizing the complications associated with these two conditions in this country.
In this study, with the aim of identifying and filling these existing knowledge gaps, we analyzed the 2016 NDHS data to investigate the "overall" prevalence and determinants of pre-hypertension and hypertension in Nepal. Our results may also be helpful for estimating this health burden in other South Asian countries with similar sociodemographic characteristics, double disease burden, and limited availability of recent data.

| Survey procedure
The 2016 NDHS was designed to make the survey nationally representative. This was a multistage survey, conducted in two and three stages in rural and urban areas, respectively. The ward was considered as the primary sampling unit in both areas. Then, in rural areas, households were selected from wards. As the wards were larger in urban areas, each ward, according to the older ward classification from the 2011 Nepal Population and Housing Census, was considered as the enumeration area (EA) in the second stage. Again, the households were selected from the EA. The survey aimed to have a total of 11 490 households. From these households, all residents aged ≥15 years were eligible for blood pressure measurements. On behalf of the household members, the head of each household provided written informed consent. With an overall 95% response rate, a total of 14 823 "un-weighted" individuals participated in the survey. The survey design, methodologies, sample size calculation, findings, and questionnaires are available elsewhere. 14

| Measurements
The survey used the UA-767F/FAC (A&D Medical) automated device to record the blood pressure of the participants. Blood pressure was measured three times in a sitting position, with a gap of 5 minutes between each measurement, and the mean of the last two measures was used to report the pressure levels. The survey used the World Health Organization 1999 guidelines (1999 WHO) to report a participant as hypertensive. 14 This guideline is currently recommended by WHO among the existing guidelines and reports, including the 2017 American College of Cardiology/ American Society of Hypertension guidelines. 24,25

| Study variables
The dependent variable for this study was hypertension. A person with a systolic blood pressure (SBP) ≥140 mmHg or a diastolic blood pressure (DBP) ≥90 mmHg was considered hypertensive. Additionally, participants exhibiting values below that pressure range for SBP and DBP but taking blood pressure lowering drugs, were considered hypertensive. An individual with either SBP or DBP between 120 and 139 or 80 and 89 mmHg, respectively, without taking blood pressure lowering drugs, was labeled as prehypertensive. The explanatory variables (ie, factors) were selected a priori based on available reports and structure of the 2016 NDHS. The independent variables were age (in years), sex, BMI (kg/m 2 ), education level, household wealth status, place (rural or urban), ecological zone (Mountain, Hill or Terai), and provinces (Provinces 1-7) of residence. Table 1 describes all study variables and their categories.

| Statistical analyses
First, the background characteristics of the study participants were described. Continuous variables with skewed distributions were reported with median and inter-quartile ranges (IQR). Categorical variables were reported with numbers and percentages. Prevalence of hypertension and pre-hypertension was determined according to the background characteristics of the study participants. Then, we conducted simple logistic regression analyses to estimate the unadjusted odds ratios (UOR) with 95% CI. Next, a multivariable analysis was conducted to estimate the adjusted odds ratio (AOR). Variance inflation factors were assessed before incorporating them into the multivariable models. Variables with a P value <0.2 in simple logistic regression were considered in the multivariable model to estimate    43.8-51.8). The overall prevalence of "stage 1" and "stage 2" hypertension was 13.5% (95% CI: 12.9-14.0) and 6.0% (95% CI: 5.6-6.4), respectively. The results of logistic regression analyses are summarized in

| DISCUSSION
In this study, we analyzed a nationally representative survey to estimate the prevalence and associated factors of pre-hypertension and hypertension in Nepal. 14 To our knowledge, this is the first nationally representative study from Nepal to present the most recent data (2016 NDHS) on prevalence and risk factors for both pre-hypertension and hypertension in relation to a range of background characteristics.  32,34 Elevated BMI is an emerging problem not only in developing countries but globally as well. 16,35,36 Although the overall proportion of obese or overweight respondents was low in this study, modifying dietary habits and lifestyles is essential to reduce the burden of obesity. Such a decrease may help prevent or control hypertension and other diseases that occur as complications of hypertension or obesity. [32][33][34] Similar to several other countries, our results show that overall prevalence and likelihood of pre-hypertension or hypertension was higher among males. [37][38][39] Both biological and behavioral differentials contribute to this major difference. 37 The 2016 NDHS report stratified prevalence according to sex and found that males had a greater prevalence than their female counterparts until 65 years of age. 14 These differences suggest that males require more awareness to maintain normal blood pressure levels than females.
In line with some studies conducted in Nepal, the prevalence and risk factors for hypertension or pre-hypertension did not show any consistent patterns of association with variables of socioeconomic conditions such as education level and wealth status. 10,17 Although wealth status had no relationship with hypertension, it had an inverse association with pre-hypertension in our multivariable analysis.
Additionally, education level had a positive association with hypertension. The higher prevalence and odds of hypertension among people with better socioeconomic conditions in developing countries primarily result from increased calorie consumption and sedentary lifestyles of these people compared with those with lower socio-economic status. 40 On the other hand, in developed countries, individuals with lower socio-economic status have a greater risk of hypertension due to consumption of high-calorie foods and having decreased awareness to control this condition. 30, 40 We did not find any significant difference in prevalence or odds according to ecological zone or rural-urban residence. However, the prevalence and odds of pre-hypertension and hypertension were higher in specific regions, such as Provinces 4 and 5. This was also observed by another study that investigated risk factors for hypertension in Nepal. 41   Given the negative consequences of hypertension, our estimations suggest that hypertension could be a huge public health challenge for Nepal, specifically for some high-risk groups such as older or obese people, similar to the situation in other countries. 12,38 The current health strategy has a specific target to reduce the prevalence of overall hypertension from 26% to 22% by 2020. 47 Achieving this target could be too difficult for a country without a high awareness level. In Nepal, studies that investigated awareness of hypertension found a low level of awareness. 19,41 In addition, only a small proportion of people were taking anti-hypertensive medications to control hypertension. 14 These reduced awareness and treatment levels may put a large proportion of people at higher risks of cardiovascular diseases. As stated previously, characteristics mainly associated with the development of pre-hypertension and hypertension, such as lifestyle and dietary habits, were beyond the scope of this analysis.
Nevertheless, the assessment of risk factor trends is imperative to understand varying prevalence and likelihoods among specific population groups. A recent study found that there is a trend towards sedentary lifestyle and the increased consumption of salty foods in a Nepalese community. These habits correlated with the prevalence of hypertension in that community. 16 Future studies should investigate the overall trends of those characteristics and causal associations in this country.
The study has several notable strengths. First, we estimated the prevalence and determinants of pre-hypertension and hypertension among a wide age range of people (≥15 years). This study is generalizable to the entire Nepalese population, as the survey covered both urban and rural areas in all seven provinces along with all three ecological zones. In addition, high response rate and a large sample size increased the reliability of the findings. Skilled survey staff used a standardized, validated method to measure the blood pressure of the participants.
Despite the above-mentioned strengths, limitations of the present study also merit discussion. The 2016 NDHS dataset was cross-sectional. Due to the uncertainty in temporality, associations observed in this study might not be causal. While the standard guidelines recommend longitudinal measurement of blood pressure with sphygmomanometers, the measurements were done with an automated device on a single day. 24,26 In addition, differences in the skill or efficacy level of survey staff may also have caused measurement errors. 18 These variations could cause some nondifferential misclassification of disease. Due to limitations of the 2016 NDHS dataset, other factors such as ethnicity, physical activity level, concomitant diabetes, smoking, alcohol consumption, or dyslipidemia that also contribute to higher prevalence or likelihood of hypertension, were not investigated in our study; future studies should investigate association of these characteristics in the context of this country.

| CONCLUSIONS
This study investigated the prevalence and determinants of pre-hypertension and hypertension in Nepal. The combined prevalence of these two conditions indicates that nearly half of the people in this country have a higher risk of cardiovascular diseases due to elevated blood pressure. As a result, at-risk individuals should adopt healthier dietary habits and more active lifestyles to prevent complications. People with certain background characteristics such as higher age, BMI, male sex, and residency in certain regions had increased prevalence and likelihood of pre-hypertension and hypertension, and there is a need to prioritize these population groups in future hypertension control and prevention strategies.