Hypertension, or high blood pressure, is diagnosed when a person’s blood pressure reading is found to be consistently above the normal range for humans, a value determined to be 130/80 mmHg1 by the American Heart Association (AHA). Yet this chronic disease affecting millions of people worldwide, often does not present with any noticeable symptoms and goes undetected for years in individuals, making it a “silent disease”. This places a significant burden on healthcare systems because if left undetected, hypertension can lead to serious health consequences
Hypertension is one of the most important risk factors for death and disability in India5 and its influence is growing with each year2,6. A majority of deaths in India today (63%) can be attributed to non-communicable diseases of which almost 27% are due to cardiovascular disease (CVD) for which hypertension is a major risk factor15. Not only does hypertension hit Indians at a younger age than western populations, its effects including first instances of heart attacks and strokes occur almost a decade earlier7.
Recent studies indicate that more than 35% of the adult Asian population is affected by hypertension, yet despite significant improvements in the awareness and treatment of hypertension in recent years, the fact remains that many individuals are still unaware of their condition, particularly those in low socio-economic groups. As per the Indian National Family Health Survey 2015-16 data only 50% of patients in the 15 – 49 years age group in India were aware of their hypertension status5 and a cross-sectional study funded by the Indian Council of Medical Research (ICMR) showed that only 5.5% of individuals self-reported having hypertension, while the actual prevalence of the condition, as measured by those reaching medical professionals, was found to be 26.3%8. This suggests that there is a significant gap in awareness and diagnosis of hypertension in India. Even amongst those detected with hypertension in India, only 20.2% of the urban population and 10.7% of the rural population manage to keep their blood pressure under control5 via medication or lifestyle. This exposes a majority of the affected individuals to an increased risk for premature death with additional burden on health care costs.
Various risk factors predispose an individual to hypertension, including age, genetics, obesity, lack of physical exercise, and smoking. This allows for some reduction in the rate through simple lifestyle changes such as maintaining a healthy weight, engaging in regular exercise, reducing salt intake, and quitting smoking9. Beyond this, medication is often necessary to try and lower blood pressure and thereby reduce the risk of complications. There are numerous classes of anti-hypertensive drugs available, such as diuretics, beta-blockers, and angiotensin-converting enzyme (ACE) inhibitors Reports note regional disparities in the management of hypertension in India, with better control rates observed in South India as compared to the western and northern parts of the country5. This may be the result of variation in healthcare systems and access, environmental or genetic factors. Regardless, management remains a challenge for many people and even with lifestyle changes and good drug compliance, refractory hypertension continues to be an issue with need for new approaches10.
Our understanding of the genetic component of hypertension remains incomplete even though heritability for hypertension is as high as 50%11. To date over 30 genes have been linked, with over 1,477 common single-nucleotide polymorphisms (SNPs) being associated. Functional mapping of the SNPs associated with blood pressure identified using Genome wide association studies (GWAS) studies is challenging since most of them are pleiotropic (DNA variants influencing multiple traits) and mapped to non-coding regions of the genome3. Technological advancements in high-throughput genotyping and sequencing have led to a better understanding of the genetic basis of hypertension, and international collaborations have made significant contributions to this research4. The contribution of both genetic and environmental factors is crucial to comprehensively study the underlying mechanisms of hypertension in order to develop new targeted therapies.
The lack of new drugs being approved for treating hypertension for more than two decades stands out as a significant barrier3. Given that our understanding of essential hypertension remains very incomplete, genomic research offers a way to gather insights on the underlying biology of individuals with hypertension and the various different subclasses. This may be possible by carefully analyzing individuals and patients, however an individual’s awareness of their hypertension cannot be directly assumed for such studies.
Interestingly, Hypertension in India presents some unique characteristics. It has an earlier age of onset7 and presents differently in different Indian populations12-14. Differences in genetic factors may therefore be able to brought to light through comparative studies though this will only be successful if the individuals are carefully phenotype as described above, That this is needed is well demonstrated in our studies in India, which have shown that 1 in 6 had elevated blood pressure on measurement that they were unaware of. Done properly however, genomic insights from the research in India may throw up extremely valuable insights for treatments in the future.
- Whelton, P. K., Carey, R. M., Mancia, G., Kreutz, R., Bundy, J. D., & Williams, B. (2022). Harmonization of the American College of Cardiology/American Heart Association and European Society of Cardiology/European Society of Hypertension Blood Pressure/Hypertension Guidelines: Comparisons, Reflections, and Recommendations. European Heart Journal, 43(35), 3302-3311.
- Boro, B., & Banerjee, S. (2022). Decomposing the rural–urban gap in the prevalence of undiagnosed, untreated and under-treated hypertension among older adults in India. BMC Public Health, 22(1), 1-16.
- Padmanabhan, S., & Dominiczak, A. F. (2021). Genomics of hypertension: the road to precision medicine. Nature Reviews Cardiology, 18(4), 235-250.
- Padmanabhan, Sandosh, Mark Caulfield, and Anna F. Dominiczak. “Genetic and molecular aspects of hypertension.” Circulation research 116, no. 6 (2015): 937-959.
- Koya, S. F., Pilakkadavath, Z., Chandran, P., Wilson, T., Kuriakose, S., Akbar, S. K., & Ali, A. (2023). Hypertension control rate in India: Systematic review and meta-analysis of population-level non-interventional studies, 2001–2022. The Lancet Regional Health-Southeast Asia, 9, 100113.
- Kearney, P. M., Whelton, M., Reynolds, K., Muntner, P., Whelton, P. K., & He, J. (2005). Global burden of hypertension: analysis of worldwide data. The Lancet, 365(9455), 217-223.
- Kodilkar, J., Agarwal, A., Baviskar, R., & Chafekar, D. (2022). Evaluation of Clinical Presentation and Various Causes of Hypertension in Young to Middle Aged Patients: An Observational Study in India. International Journal of Pharmaceutical and Clinical Research, 14(3); 147-159.
- Bhansali, A., Dhandania, V. K., Deepa, M., Anjana, R. M., Joshi, S. R., Joshi, P. P., … & Pradeepa, R. (2015). Prevalence of and risk factors for hypertension in urban and rural India: the ICMR–INDIAB study. Journal of human hypertension, 29(3), 204-209.
- World Health Organization. (2021). Hypertension. https://www.who.int/news-room/fact-sheets/detail/hypertension
- Matanes, F., Khan, M. B., Siddiqui, M., Dudenbostel, T., Calhoun, D., & Oparil, S. (2022). An update on refractory hypertension. Current Hypertension Reports, 24(7), 225-234.
- Ehret, G. B., & Caulfield, M. J. (2013). Genes for blood pressure: an opportunity to understand hypertension. European heart journal, 34(13), 951-961.
- Midha, T., Lalchandani, A., Nath, B., Kumari, R., & Pandey, U. (2012). Prevalence of isolated diastolic hypertension and associated risk factors among adults in Kanpur, India. Indian heart journal, 64(4), 374-379.
- Gupta, S., & Kapoor, S. (2013). Genetic and environmental influences on blood pressure in an urban Indian population. Journal of biosocial science, 45(1), 1-11.
- Borah, P. K., Mahanta, J., Kalita, H. C., & Bhattacharjee, C. K. (2020). Distribution of hypertension subtypes in a hill tribe of Mizoram, Northeast India. Indian heart journal, 72(5), 398-402.