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Harvard queries Indian heart disease ‘reversal’ claim

New Delhi, April 8: Repeated assertions by a lobby of influential doctors over the past decade that India’s burden of heart disease is shifting from the rich to the poor are misleading and premature, a new study has said.

Researchers at Harvard University have said these past assertions about a reversal of heart disease patterns in India relied on studies with sampling biases and did not reflect nationwide trends. Their findings have just been published in the International Journal of Epidemiology.

“The available data do not support any such reversal on a nationwide scale,” S.V. Subramanian, a professor of population health and geography at the Harvard School of Public Health who led the new study, told The Telegraph.

Subramanian and his colleagues reviewed dozens of earlier studies from India over the past two decades that had probed links between risk factors for heart disease and socio-economic status measured through income or education.

Their analysis confirms that smoking and low consumption of fruits and vegetables are two risk factors for heart disease that seem more prevalent among the poor than the rich.

But the prevalence of other risk factors such as diabetes, obesity, unhealthy cholesterol levels and high blood pressure — as well as the proportion of deaths from heart disease — continue to be higher among higher socio-economic groups, the researchers said.

Since 2003, several cardiologists and public health researchers have published papers suggesting the poor are becoming increasingly vulnerable to heart disease in India. They have linked the purported trend to changing lifestyles and dietary habits.

“This pattern is clearly visible. Many doctors in the field, including those in rural areas, have noticed it,” said K. Srinath Reddy, cardiologist and president of the Public Health Foundation of India, a research and education institution.

“The reversal doesn’t happen simultaneously with all risk factors. It’s first seen with smoking, then with high blood pressure, then with cholesterol and diabetes, and finally with the lack of physical activity,” Reddy told this newspaper.

But the Harvard team says the studies used to support such assertions drew on samples that cannot be extrapolated across India or contain a discrepancy between data and interpretations, drawing conclusions “discordant with their own results”.

“I think this is well-intentioned but misleading interpretation of data,” said Malavika Subramanyam, a physician who took part in the study last year as a doctoral student at Harvard and is now an assistant professor of social sciences at IIT Gandhinagar.

A study from Jaipur had claimed that people with low and middle education had a greater risk of heart disease than the highly educated, but had actually observed that most risk factors, except smoking, were more prevalent in those with better education.

A study by Reddy and his colleagues that indicated the poor were increasingly vulnerable to heart disease had relied on the employees of industries and their families.

Malavika Subramanyam has questioned the relevance of such a sample to India’s labour force outside industries. A 2012 estimate says that about half of India’s workforce is still engaged in labour-intensive agricultural activities.

“If this had no consequence, we needn’t worry about it,” S.V. Subramanian said. “But an over-emphasis on heart disease and stroke may work against other diseases, given the limited resources available for health in India.”

He added: “Government funds channelled into cardiovascular disease, still essentially a rich person’s disease in India, might proportionately lower the resources available for diseases that affect the poor.”

Public health researchers believe the findings of the Indian studies were among factors that convinced the Centre to launch a national programme on prevention and control of cardiovascular disease, diabetes, cancer and stroke.

The programme is operational in 100 districts across 21 states. Doctors who led the studies in India assert that risk factors for heart disease are indeed prevalent in “worrying proportions” among the poor.

“Statistics may be interpreted in different ways,” said Rajeev Gupta, a cardiologist in Jaipur who was involved in several such studies. “Even a low load of risk factors in the poor would translate into millions of people. This is a public health emergency.”

“One major risk factor for high blood pressure and diabetes in adults is low birth weight,” said Dorairajan Prabhakaran, a cardiologist and executive director of the Centre for Chronic Disease Control, New Delhi, who was involved in the study that examined industrial workers and their families.

“Low birth weight is so widely prevalent among the poor that we are actually sitting on a time bomb.”

The Harvard researchers say that a low-weight mother is a key predictor for low birth-weight babies, and that this highlights the need to allocate resources to improve the health of mothers.