Air pollution and the heart: Is the invisible enemy more dangerous than the winter chill?

When a trend belies expectations, look beyond the obvious and investigate.

- DR HEMANT MADAN

For decades, cardiologists have observed a recurring seasonal pattern in clinical practice. The frequency of heart attacks tends to increase during winters. Not only this, patients with preexisting heart disease, tend to deteriorate during the colder months. They need more frequent and longer hospitalisations.

Traditionally, this surge in cardiac complications has been attributed to the physiological effects of low temperatures. Wintry weather results in an elevation of blood pressure due to a combined effect of blood vessel constriction and an excessive accumulation of salt in the body (due to reduced sweating). Lack of physical activity combined with a tendency to indulge in richer, heavier food, team up to result in an increase in body weight, elevation of blood sugar and cholesterol levels. All these contribute to a significant increase in the metabolic load on one’s cardiovascular system, leading to the spurt in these cardiovascular events.

While the above-mentioned explanations seemed adequate and enough thus far, they do not somehow, align with present-day realities. So, are we missing an invisible elephant in the room?

Thanks to global warming, winters in North India are noticeably milder and shorter than they were a few decades ago. The sharp dip in temperature, that once defined the season, has softened. If winter temperature was the only reason for an increase in cardiac events, a reduction in the winter chill should have resulted in a reduction in the incidence of cardiac events. Yet, this has not happened. The winter surge in cardiac events not only persists but has in fact worsened.