Study design

This cross sectional study utilizes secondary data from the fifth National Family Health Survey (NFHS-5), which is the Indian version of the Demographic and Health Survey conducted regularly in more than 90 countries worldwide. NFHS is a collaborative project supported by the International Institute of Population Sciences (IIPS) in Mumbai, India; International Classification of Functioning, Disability and Health (ICF) in Calverton, Maryland, USA, and East West Center in Honolulu, Hawaii, USA. The Ministry of Health and Family Welfare (MoHFW) of the Government of India has appointed IIPS as the coordinating and technical guidance agency of NFHS. The survey is funded by the United States Agency for International Development (USAID) with additional support from the United Nations Children’s Fund (UNICEF). NFHS uses four different types of questionnaires such as household, man’s, woman’s and biomarker in 19 languages using the Computer Assisted Personal Interviewing (CAPI). The fieldwork for NFHS-5 in India was done in two phases. Phase one took place between June 17, 2019, and January 30, 2020, which covered 17 states and 5 Union Territories. Phase two was conducted between January 2, 2020 and April 30, 2021, which covered 11 states and 3 Union Territories. A total of 17 Field Agencies gathered data from 6,36,699 households, 1,01,839 men and 7,24,115 women.

Data source

The current data analysis uses the men’s questionnaire and women’s questionnaire from NFHS- 5, mainly focusing on male and female datasets. It focuses on the various independent factors associated with hypertension (dependent variable) among Indian adults.Analyzing the male and female factors separately can provide a clear understanding on the social and cultural factors associated with hypertension. Potential confounding variables such as dietary sodium intake, psychological stress, and family history of hypertension were not included due to limitations in the NFHS-5 data collection instruments. It examines the ideal age points at which the Indian adult population has to be screened for hypertension. Usually, the age cut off for screening hypertension has been taken as 30 years and the evidence provided through a nationwide survey would be more convincing regarding the appropriate age cut off. The total sample size utilized for this secondary data analysis was 1,01,839 men and 7,24,115 women aged 15 years and above. Since there are missing values, each variable in this analysis has a different sample size, as mentioned in the results section.

Ethical approval

The research was conducted using a pre-existing, anonymised data from a public source, which did not require direct involvement of the patients or the general public. Since the dataset did not contain any personally identifiable information about the study participants, a formal ethics committee approval was not mandatory. However, the ethics committee approval was obtained from the Institutional Ethics Committee of the Post Graduate Institute of Medical Education and Research (PGIMER) in Chandigarh (approval number IEC-08/2022–2535, dated 17.08.2022).

Definitions

As per the guidelines of World Health Organisation (WHO) and American Heart Association (AHA), the study describes elevated blood pressure as having a systolic blood pressure of 140 mmHg or higher and/or a diastolic blood pressure of 90 mmHg or more [16]. The raised risk of metabolic complications was considered when the waist-hip ratio (WHR) was 0.90 or higher for men and 0.85 or higher for women [17]. Regions were divided into 6 categories namely north (Chandigarh, Delhi, Haryana, Himachal Pradesh, Jammu & Kashmir, Punjab, Rajasthan, Uttarakhand), central (Chattisgarh, Madhya Pradesh, Uttar Pradesh), east (Bihar, Jharkhand, Odisha and West Bengal), northeast (Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim and Tripura), west (Dadra & Nagar Haveli, Daman & Diu, Goa, Gujarat, Maharashtra) and south (Andaman & Nicobar Islands, Andhra Pradesh, Karnataka, Kerala, Lakshadweep, Puducherry, Tamil Nadu and Telangana).

Statistical analysis

Hypertension was identified as the outcome variable in the study. The average of three blood pressure readings that were collected during the NFHS was considered for the study. The quantitative blood pressure values were then converted into a dichotomous variable as presence or absence of hypertension. Sampling weights were incorporated into the data to address the differential probabilities of selection and participation.

Statistical analysis was performed using IBM SPSS version 20. The data were presented in the form of mean with 95% confidence interval (CI), frequency and percentage. The associations were evaluated using multivariable logistic regression analysis to calculate the adjusted odds ratio and 95% CI of raised blood pressure with age category (8 categories), marital status, religion, educational status, wealth index (5 categories), occupation, residence, region (6 categories), caste, waist-hip ratio, alcohol use, tobacco use, fruit intake, fried food intake and co-morbidities. The fitness of the dataset was assessed using the Hosmer and Lemeshow test and the Goodness of Fit test. Receiver Operating Characteristics (ROC) Curve was used to evaluate and compare the performance of classification models (age) where the outcome variable is binary (raised blood pressure: present/absent). Sensitivity and specificity was used to describe the diagnostic ability of the screening test. The Youden index was used as a summary measure of the ROC curve to select the optimal cut off point for the age within the age group.A p value of less than 0.05 was considered as significant. Missing data were handled by listwise deletion. Participants with missing values for outcome or explanatory variables were excluded from respective analyses. No imputation was performed. Sample sizes for each analysis are reported in the tables to reflect variations due to missing data.

Comparison with global and national trends

Globally, the prevalence of hypertension among adults was 32% in women and 34% in men in 2019, with 41% of women and 51% of men being unaware of their hypertensive status [1]. This study’s findings align with global trends, showing a linear increase in blood pressure with age, emphasizing the need for timely detection. The study identifies the age group of 35–39 years as a critical point for initiating hypertension screening, suggesting that approximately 60% of adults in this age group have elevated blood pressure, a statistic that parallels the 60% sensitivity identified in the current study [5].

The World Health Organization (WHO) emphasizes opportunistic screening for all adults in primary care settings but does not recommend a specific age threshold [18]. The US Preventive Services Task Force (USPSTF) recommends annual hypertension screening for adults aged ≥40 years or younger adults with risk factors, and every 3–5 years for those aged 18–39 years without risk factors [5]. The Indian NPCDCS program currently recommends annual screening starting at 30 years of age [19], but this recommendation lacks age-stratified evidence from large-scale national datasets. Our study contributes by empirically identifying 36.5 years as the optimal cut-off based on ROC analysis, offering the first age-specific evidence from a nationally representative Indian sample (NFHS-5). Compared to prior Indian studies such as Prenissl et al. (2019), which highlighted awareness gaps but did not define an ideal screening age [20], our findings offer direct policy guidance.

In India, the National Family Health Survey (NFHS-5) data highlights a gap in hypertension awareness, with only 27% of hypertensive individuals aware of their condition, 14.5% receiving treatment, and just 12.6% having controlled blood pressure [2]. These figures underscore the need for improved screening strategies. This study further suggests that starting screening at 35 years could potentially capture a significant portion of undiagnosed cases, contributing to the national goal of reducing hypertension prevalence by 25% by 2025 [21].This gap in awareness and management is concerning, especially considering the high prevalence of hypertension, which is a major risk factor for cardiovascular diseases, including stroke and heart attacks [22].

One of the critical challenges in managing hypertension in India is the low rate of awareness. Studies have shown that lack of awareness is often due to the asymptomatic nature of hypertension, where individuals do not experience symptoms until significant damage has occurred to vital organs [23]. This underlines the importance of regular screening to identify individuals with elevated blood pressure before complications arise.

Moreover, the treatment rates for hypertension are alarmingly low. Even among those diagnosed, the rate of treatment is just 14.5%, indicating significant barriers to accessing healthcare, such as economic constraints, lack of healthcare infrastructure, and inadequate follow-up [24]. Cultural beliefs and practices also play a role in influencing health-seeking behavior, with many individuals relying on traditional medicine or home remedies instead of seeking formal medical treatment [25].

The control rate, with only 12.6% of hypertensive individuals maintaining their blood pressure within recommended levels, highlights the challenges in ongoing management and adherence to treatment regimens [2]. Poor adherence to prescribed medication, often due to side effects, lack of understanding of the chronic nature of hypertension, and the financial burden of long-term treatment, are significant factors contributing to this issue [26].

Given these challenges, the study suggests that initiating hypertension screening at age 35 could play a crucial role in capturing a significant portion of undiagnosed cases. The age group of 35–39 years is identified as a critical period where the prevalence of hypertension begins to rise sharply. Within this age group, the study found that 56.4% of males and 60.9% of females have elevated blood pressure, underscoring the importance of early detection [27].Early screening is essential because evidence shows that hypertension detected and managed early significantly reduces the risk of cardiovascular events later in life. For example, the Framingham Heart Study demonstrated that individuals who developed hypertension by their mid-30s had a markedly higher lifetime risk of cardiovascular disease, including heart failure, myocardial infarction, and stroke [28].

The benefits of early screening are further supported by findings from the SPRINT trial, which showed that intensive blood pressure management in individuals at risk significantly reduced the rates of cardiovascular events and all-cause mortality [29]. Additionally, a systematic review of hypertension management strategies in low- and middle-income countries highlighted that early detection through community-based screening programs effectively reduces the burden of hypertension-related complications [30].

Socio-demographic determinants

This study reveals a significant association between marital status and diastolic blood pressure (DBP), with married men exhibiting a 12% increased risk of elevated DBP compared to their unmarried counterparts. This finding resonates with previous studies indicating that married individuals, particularly men, may experience higher blood pressure due to marital stress [31]. However, this stress-related increase in DBP needs to be balanced against the generally recognized health benefits of marriage, such as better social support and health behaviors [32].

The study also highlights a 10% lower risk of hypertension among Muslims compared to Hindus. This difference could be attributed to religious practices such as fasting during Ramadan, which has been shown to have beneficial effects on cardiovascular health [27]. Further, dietary habits prevalent in Muslim communities, such as lower consumption of alcohol and possibly higher consumption of whole grains and legumes, may contribute to this reduced risk [33].

Education and wealth index were also significant predictors of hypertension. The study found that individuals with no formal education had a 20% higher risk of hypertension compared to those with higher education. This is consistent with global data suggesting that lower educational attainment is associated with poorer health outcomes due to factors like reduced health literacy and access to healthcare services [34]. Moreover, the wealth index showed a clear gradient, with individuals in the highest quintile being 35% more likely to have elevated DBP, possibly due to lifestyle factors such as higher dietary intake of fats and sugars [35].

Behavioral and physiological risk factors

Behavioral risk factors, particularly alcohol consumption and obesity, showed strong associations with hypertension in this study. Men who consumed alcohol were 28% more likely to have elevated systolic blood pressure (SBP), while those with a high waist-hip ratio (WHR) had a 46% higher risk of elevated SBP and a 62% higher risk of elevated DBP [36]. These findings are supported by global statistics that link excessive alcohol consumption to an increased risk of hypertension due to its effects on the cardiovascular system [12].

Obesity, as indicated by WHR, is a well-established risk factor for hypertension, with studies showing that a 5 kg/m² increase in body mass index (BMI) can increase the risk of hypertension by 49% [37]. The study’s findings that higher WHR correlates with a substantial increase in hypertension risk emphasize the need for weight management interventions as part of hypertension prevention strategies.

Interestingly, the study reports a protective effect of fried food consumption on DBP, particularly in women, with those consuming fried foods weekly having a 24% reduced risk of elevated SBP and a 17% reduced risk of elevated DBP. This finding is contrary to the general understanding that fried foods, typically high in trans fats and sodium, contribute to hypertension [38]. This unexpected result suggests that other factors, such as the type of oils used or the presence of other healthy behaviors, might be influencing these outcomes. For instance, some traditional Indian cooking practices involve the use of oils rich in unsaturated fats, which might offset the negative effects of frying [39]. Further research is needed to disentangle these associations and understand the complex dietary patterns at play.

The study also highlights a gender difference in the impact of fruit intake on blood pressure, with daily fruit consumption associated with a 20% reduced risk of elevated DBP in men, but not in women. This difference could be due to variations in the types of fruits consumed or the overall dietary context in which fruit is eaten. Fruits are rich in potassium, which has been shown to counteract the effects of sodium and lower blood pressure [40]. However, gender differences in nutrient metabolism or hormone levels may modify this protective effect, warranting further investigation.

Implications for public health and policy

In India, the Ministry of Health and Family Welfare (MoHFW) recommends hypertension screening starting at age 30 [21]. However, this study suggests that screening should be intensified from age 35 to capture those at risk earlier, as evidence suggests that undiagnosed hypertension in this group leads to increased cardiovascular morbidity later in life [31]. Studies have shown that hypertension in individuals aged 35–44 is associated with a significantly higher risk of cardiovascular events, including heart attacks and strokes, compared to those diagnosed later in life [27,32]. Furthermore, data from the Framingham Heart Study indicate that individuals who develop hypertension by their mid-30s have a higher lifetime risk of cardiovascular disease, emphasizing the importance of early detection and management [33]. Additional research from the INTERHEART study confirms that the early onset of hypertension, particularly before age 40, substantially increases the risk of myocardial infarction, making early and targeted screening interventions crucial [34].

Based on the identified ROC thresholds and age-specific risk profiles, we recommend revising India’s hypertension screening guidelines to initiate routine screening from 35 years onward for both men and women. This adjustment balances feasibility with early detection impact, especially considering that SBP begins to rise substantially from this age group onward.

The study’s findings also highlight the need for integrated public health strategies that address the underlying socio-economic and behavioral determinants of hypertension. For instance, public health campaigns should promote lifestyle changes such as reducing alcohol intake and managing body weight, particularly among younger adults. Given that only 14.5% of hypertensive individuals in India are receiving treatment, there is a clear need for improving access to care and ensuring that screening programs are effectively linked to treatment and follow-up services [2]. Moreover, educational interventions aimed at improving health literacy could play a crucial role in reducing hypertension prevalence. The study’s findings that lower educational attainment and wealth are associated with higher hypertension risk underscore the importance of addressing these social determinants of health through targeted public health interventions [41].

Limitations and future research

While this study provides valuable insights, it has limitations that should be acknowledged. The cross-sectional design limits the ability to establish causality between the identified risk factors and hypertension. Future research should focus on longitudinal studies to better understand the temporal relationships and causality [14]. Additionally, the reliance on self-reported data for alcohol and tobacco use may introduce recall bias, potentially leading to underestimation of these behaviors’ impact on hypertension [42]. We acknowledge the possibility of regional disparities in healthcare access, awareness, and hypertension screening practices across different states and zones in India, which may influence screening rates and outcomes. This warrants further subnational analysis.

The study also did not include detailed dietary assessments, particularly sodium intake, which is a key contributor to hypertension. The average sodium intake in India is estimated to be over 10 grams per day, which is more than double the World Health Organization’s recommended limit of 5 grams per day [43]. Future studies should incorporate detailed dietary data, including sodium and potassium intake, to better understand their roles in hypertension in the Indian context [44].