A new look at the cardiovascular crisis in India
Cardiovascular disease in India has quadrupled in the last 40 years and WHO estimates that by 2020 close to 60 percent of cardiac patients worldwide will be Indian. The established risk factors of cardiovascular disease include lack of exercise, poor diet, and smoking. The emerging field of environmental cardiology addresses exposures to chemicals and other environmental substances that also have a profound impact on heart health. Divya Pamnani reviews the research and its implications for developing countries including India
We’ve heard this all before – that the cardiovascular crisis is glaringly evident in developing countries, and especially in the India. While India is still trying to shake off diseases rooted in poverty, both their urban and rural areas are experiencing a mounting epidemic of cardiovascular disease, which was until recently considered a disease of the ‘urban rich’. And unfortunately, the toll promises to grow-largely because the risk factors for cardiovascular disease are pervading low-income groups and because these populations are still youthful.
Certainly the most important reason for this epidemic is that people are living longer. Other reasons relate to the economic and cultural influences of globalisation. The resulting explosive and chaotic urbanization has come with profound lifestyle changes. Among these changes include junk food replacing the dietary fiber of the complex carbohydrates of fruits and vegetables; Resulting in an increased consumption of fat and salt, while that of micronutrients diminishes. The sad truth is, per rupee spent, junk food provides far more calories than fruits and vegetables. As calorie intake increases and physical activity diminishes, the mismatch between energy intake and energy output manifests in a pandemic of obesity and diabetes. Added to this conundrum is the rising consumption of tobacco. The outcome is as tragic to say the least, evident is the abysmal statistics.
According to a research report by the Escorts Heart Institute and Research Centre, New Delhi, India, it predicts that prevalence rates of CVD in rural populations will remain lower than that of urban populations; but it will continue to increase however, reaching around 13.5 percent of the rural population in the age group of 60-69 years by 2015. Further, the prevalence rates among younger adults (age group of 40 years and above) are also likely to increase. The report goes on to say that within a decade, heart afflictions will overtake infectious diseases and will account for half of all fatalities in the country. Contributing to the rising toll of cardiovascular disease is the high number of Indian subjects with type 2 diabetes; which is already the highest in the world. The impact on society will be far greater than in other countries since Indians have heart attacks at a much younger age. According to an article ‘A Race against Time: The Challenge of Cardiovascular Disease in Developing Countries’, in India about 50 percent of CVD-related deaths occur among people younger than 70, compared with about 22 percent in the West.
So what’s new?
The field of environmental cardiology is relatively new. A keyword search in Pubmed for ‘environmental cardiology’ yields 1816 results. A lot of research is underway at the moment, mainly focusing on environmental factors and possible correlations with CVD. Evidence has slowly been building to indicate that exposures to chemicals and other environmental substances can have a profound impact on heart health, going beyond lung disease and breathing disorders. The link between environmental agents and CVD was once considered unsubstantiated by much of the medical and scientific establishment. But after witnessing the evidence accumulate over the years, with a surge in the past 10 years, more and more scientists, doctors, and organisations are acknowledging the significance and implications of a field that is today known as environmental cardiology.
It started out as research finding links between smoking and CVD, and then moving on to secondhand smoke as well, against which evidence was surmounting. Tobacco smoke was one of the earliest environmental factors to be linked with CVD, also known to be the most distressful. In forthcoming years, there were several more discoveries which led researchers to believe that environmental factors needed a closer look. The notion of environmental cardiology was no longer considered outlandish after epidemiological studies and studies of biological processes, found numerous links between different chemicals and CVD. The subject started gaining popularity in the conference circles and even started to feature in the public conscious, reinforcing the belief that there was more to pollution than lung disease and breathing disorders as traditionally perceived.
What exactly are we talking about?
It is the ambient air particles including fine particles, ultrafine particles and nanoparticles; atmospheric gases also called ‘copollutants’ such as ozone, carbon monoxide, sulfur dioxide and nitrogen oxides; and metal pollutants such as arsenic, lead and mercury. Given the evidence so far, fine particulates appear to be one of the primary environmental factors linked with CVD and are drawing much of the research interest. According to findings by Harvard environmental epidemiologists a significant link between ambient urban air pollution, especially fine particulates, and increased deaths caused by cardiopulmonary disease, along with increases in lung cancer. Several replicated studies then ensued.
These studies show that in more than half a million people over 16 years, fine particulates were more strongly linked with deaths from cardiovascular causes than with deaths from respiratory causes. The pattern of cardiovascular deaths was consistent with evidence that mechanistic pathways linking exposure and death included pulmonary and systemic inflammation, accelerated atherosclerosis and changes in cardiac autonomic function (as measured by changes in heart rate variability).
In addition to particulates, dozens of other substances have been identified, which play some role in CVD. The United States Environmental Protection Agency, (EPA) criteria air pollutants which include ozone, carbon monoxide, nitrogen oxides, sulphur dioxide, and lead, have some evidence linking them with CVD, as do at least 17 of the 87 drinking water contaminants monitored by the EPA. In addition, many contaminants tracked in the Centers for Disease Control and prevention USA (CDC) biomonitoring project have CVD links. In this article, ‘Environmental Cardiology: Studying Mechanistic Links between Pollution and Heart Disease’, Dr Bhatnagar talks about these environmental determinants. Essentially, the author of this article opines that although the effects of genetic traits and environmental factors cannot be entirely disentangled, it has been estimated that more than 70 percent stroke, 80 percent CAD, and 90 percent of adult-onset diabetes could be attributed to modifiable, non-genetic factors, suggesting that the environment is a strong determinant of CVD risk.
Several occupational exposures also have been associated with CVD, including exposures to vinyl chloride (used to produce polyvinyl chloride and industrial solvents), carbon monoxide (a common exhaust gas), and allylamine (used in ion exchange resins, pharmaceuticals, and water-soluble polymers). Environmental risk factors such as toxins, industrial waste, aerosol contamination, chemical preservatives in food, and pesticides in agriculture are beginning to be looked at as potential predisposes to CVD.
In addition, there is also growing evidence that prenatal exposures to some environmental pollutants, such as solvents, pesticides, and dioxins, may result in subtle functional abnormalities that show up as disease in adulthood. Specific relation between prenatal exposure and coronary artery disease is unknown but prenatal exposure of the environmental toxins and congenital heart disease is likely.
In addition to these, other chemical exposures have also been linked with CVD. The most extensive evidence has been obtained with arsenic and metals. Exposure to inorganic arsenic, mainly in drinking water, has been associated with increased mortality from cardiovascular and cerebrovascular disease, hypertension, ischemic heart disease and carotid atherosclerosis.
Although exact mechanisms by which particulates, tobacco smoke or pollutants affect heart disease are not known, it is likely that long-term mutagenic changes, which are key steps in carcinogenesis, are also relevant to the development and progression of cardiovascular disease. It is also widely recognised that pulmonary effects of environmental pollutants could indirectly impair cardiovascular health, explains Dr. Bhatnagar, the author of “Environmental Cardiology: Studying Mechanistic Links between Pollution and Heart Disease”.
There has been much growth in the West in the last few years. One group that is beginning to embrace environmental cardiology is the American Heart Association (AHA), an 80-year-old organisation that has traditionally focused on risk factors such as poor diet and lack of exercise as some of the most important contributors to CVD. In the June 1, 2004 issue of ‘Circulation’, an expert panel of 11 researchers and physicians published an AHA Scientific Statement that concluded that air pollutants, one of the major environmental exposure sources under investigation by environmental cardiologists, pose a ‘serious public health problem’ for CVD. This is the first official AHA acknowledgment of such links.
A few other US government agencies, such as the National Heart, Lung, and Blood Institute (NHLBI), have also begun to address the links between environmental agents and CVD, as have advocacy organisations such as the American Lung Association and the Natural Resources Defense Council. And the NIEHS, one of the original players in the environmental cardiology arena, has ramped up its efforts to explore this area of research.
There is still a long way to go before environmental cardiology is fully embraced as a medical paradigm. Many major public health organizations, such as the WHO and the Centers for Disease Control and Prevention (CDC), have yet to fold this concept into their prevention efforts in any significant way. And there is very little trickle-down into the typical doctor-patient relationship. Nonetheless, environmental cardiology shows signs of increasingly becoming a factor in research, public health policy discussions, as its presence spreads into journals, conferences, textbooks, e-mail discussion groups, and continuing medical education courses.
Status-quo in India
Environmental cardiology should be a significant public health concern in India, but it is not. With the ever increasing CVD burden, fast pace of industrialization, and vehicle pollution in India rethinking preventive efforts is a must need. The lack of a public response to the increasing risk for cardiovascular disease thus far is due mostly to a perception among policy makers and the public that cardiovascular disease is largely a problem of the urban rich. This is far from the reality evident in the statistics in India.
Research bodies and institutes like Indian Council of Medical Research (ICMR) and National Institute of Occupational Health (NIOH) need to address these research topics on their agenda. It is apparent then that there is a lack of awareness among the cardiologists on the perils of pollution. Even the Cardiology Society of India has failed to acknowledge the efforts of other scientists around the globe working on environmental cardiology. None of their CME programmess include any update on ambient air pollutants or other pollutants. Lastly, the issue of environmental cardiology needs to seriously be addressed in public policy initiatives, to curb pollution.
(The author has done her Bachelor of Science in Psychology and Biology at the University of Texas at Austin. She can be contacted at firstname.lastname@example.org)