|Year : 2013 | Volume
| Issue : 1 | Page : 1-3
Hypertension: The prevention paradox
Director-Professor and Head, Department of Health Education, All India Institute of Hygiene and Public Health, Kolkata, India
|Date of Web Publication||4-May-2013|
Director-Professor and Head, Department of Health Education, All India Institute of Hygiene and Public Health, Kolkata
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Dobe M. Hypertension: The prevention paradox. Indian J Public Health 2013;57:1-3
At this time of the year, a lot of activity in the public health calendar centers around the World Health Day. This year, we have woken up to the challenges of tackling the rising threat of "Hypertension."
This challenging issue, high blood pressure, has been deliberated and discussed at length over the years, and a wealth of technical know-how is now available for better screening and treatment. However, some observations necessitate rethinking the priorities for addressing this challenge.
The distribution and determinants of risk of hypertension in a population have major implications for strategies of prevention. According to Geoffrey Rose, nature presents us with a processor continuum, not a dichotomy for the vast majority of diseases. The risk typically increases across the spectrum of a risk factor. Use of dichotomous labels such as "hypertensive" and "normotensive" is therefore for operational convenience. Hence, the "deviant minority" (hypertensive) are only part of a risk continuum, rather than a distinct group. This leads to one of the most fundamental axioms in preventive medicine: "a large number of people exposed to a small risk may generate many more cases than a small number exposed to high risk." A preventive strategy focusing on high-risk individuals will thus deal only with the margin of the problem and will not have any impact on the large proportion of disease occurring in the large proportion of people who are at moderate risk, for example, people with slightly raised blood pressure suffer more cardiovascular events than the hypertensive minority. High blood pressure, or hypertension, is thus also called the "silent killer." Hence, a high-risk approach may appear more appropriate to individuals and their physicians. However, it can only have a limited effect at a population level. It does not alter the underlying causes of illness, and requires continued and expensive screening for new high-risk individuals.
High blood pressure is estimated to cause 7.1 million deaths globally (13% of the total). It has been estimated that a reduction in salt intake to 6 g per day (more than that required for physiological needs) will result in a 13% reduction in mortality due to stroke and a 10% reduction in mortality due to heart disease.
Lifestyle factors can greatly contribute to hypertension, and actions toward their modification will certainly decrease the risk for developing the disease. Obesity and inactivity result in hypertension. As a result, the heart has to work harder and more blood has to be pumped through the body. Eating high amounts of sodium/salt increases the blood pressure due to increased fluid retention. Smoking and drinking alcohol narrow the blood vessels and damage the heart, which finally lead to hypertension over time. Consistent high levels of stress dramatically increase the blood pressure.
There is a robust body of evidence for the association of excess salt consumption and hypertension. Reducing salt intake has never been more relevant than it is today. Salt, an essential nutrient, was only added to food 5000 years ago. Now our consumption is 20-30 times greater than 5000 years ago. Salt has been used for food preservation, and for adding flavor and texture to foods. Now, with modern technology and alternatives to salt as a preservative (chilling, refrigeration, etc.) salt should play a lesser role in the modern diet.
The average intake of salt in many countries including India is above 9 g, which is against the WHO recommended (1985) norm of 5 g. We only need 4 g salt per day for physiological functions. Only 20% our salt intake is discretionary and 80% is obligatory. While processed food is the dominant source for salt, unrestricted and uninformed use also contributes to the higher salt intake in India. The rising trend in the consumption of processed food in India has led to a 24-30% prevalence of hypertension in urban areas, and 12-14% in rural areas. An Indian Council of Medical Research (ICMR) survey in 13 states in 1986-1988 shows that an adult consumes 13.8 g salt per day. Changes in diet and food consumption patterns are driven by increasing affluence, perceived lack of time, increase in availability and affordability of convenience foods, increasing tendency to eat out rather than prepare food at home, an increased globalization of trade, and a demand for all-year-round supplies.
Higher salt intake has a dose-dependent association with incidence of strokes and total cardiovascular events. Each year a 5 g per day reduction in salt intake at the population level could avert more than a million deaths from stroke and almost three million deaths from cardiovascular disease worldwide. Metaanalysis of 17 studies  showed that a 5 g/day reduction in salt intake is associated with a decrease in blood pressure of 4.96/2.73 mm Hg in hypertensives and 3.6/1.6 mm Hg in normotensives, supporting a population approach to salt reduction. India consumes 55-58 lakh tons of edible salt annually and can reduce incidence of stroke by 25% and heart attacks by 10% by cutting down on salt consumption.
A three-decade long effort by Finland to reduce sodium levels by about 30% has resulted in a 75% reduction in cardiovascular disease in those less than 65 years and the stroke rates have fallen by more than 70% in Japan.
A decreasing incidence, as well as deaths, will reduce the burden on the health services for stroke rehabilitation and heart disease interventions. Access to cardiac services, angiography, angioplasty, etc. will be more readily available to those with other risk factors.
Choices need to be made between different strategies for risk reduction and decision made on the most appropriate and effective mix of these strategies. A key challenge is finding the right balance between different approaches. In practice, there is rarely an obvious and clear choice. Strategies are usually combined so as to complement each other. They can be categorized broadly as:
Focus on "upstream" approaches alongside the traditional "downstream" approach. Given that 80% of our salt intake is obligatory (added to food during processing, preparation, or preservation), we should urgently look for "upstream measures," such as healthy policies of procurement, and engage with the food industry to reduce salt intake.
- Interventions that seek to reduce risks in the population as a whole: These include interventions by governments through legislation, taxation, and health promotion campaigns targeting the public. In reducing risks from blood pressure, shifting the mean of whole populations will be more cost-effective in avoiding future heart attacks and strokes than screening programmes that aim to identify and treat all those people with defined hypertension.
- Interventions that target individuals within the population : These include strategies to change risk behaviors of individuals (e.g., excessive salt consumption), often through personal interaction with a health provider and risk communication. People's risk perceptions are based on a diverse array of information, which are inherently difficult to communicate. The mass media-newspapers, magazines, radio, and television-do have a powerful influence on people's perceptions of risks and should be judiciously used for risk communication.
Population wise salt reductions involve
When attempting to reduce the salt intake by populations, the issue of salt iodisation must also be taken into consideration. A comprehensive strategy that effectively encompasses both public health problems must be developed.
- Voluntary cooperation between the government and the food industry to include appropriate labelling about the salt content on products and to ensure a stepwise reduction of salt in commonly consumed processed foods. This could be through initiatives such as the development of voluntary codes of conduct.
- Legislative action to ensure a reduction of salt in processed foods with appropriate labelling and enforcement of quality control. Costs of such action are higher than the voluntary efforts, but effects on salt intake reduction are also likely to be more. Many countries have already taken the lead in cutting down on salt consumption. Finland, Japan, and the United Kingdom have mandated reductions in salt content in processed food items. The United States requires mandatory labelling of sodium content.
- In India, the 24-30% prevalence of hypertension in urban areas, and 12-14% in rural areas, along with the rising trend in the consumption of processed food, call for urgent steps to limit salt levels in processed food and to build public awareness on the need to consume less salt. There is huge potential for major gains through sustained intersectoral action involving other concerned ministries and agencies.
It is time for us to close ranks against the growing threat of hypertension in India.
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