Inactivity Is a Universal Risk Factor for Heart Attack

January 11, 2012

January 11, 2012 (Uppsala, Sweden) — A new analysis of the INTERHEART study, drilling down into exactly how physical activity and its different components contribute to the risk of MI, doesn't turn up any huge surprises but does confirm that inactivity is "a universal cardiovascular risk factor," lead author Dr Claes Held (Uppsala Clinical Research Center, Uppsala, Sweden) tells heartwire [1]. Held and colleagues publish the results online January 11, 2012 in the European Heart Journal.

In fact, the findings reveal a large discrepancy between physical-activity levels in different economies, Held notes, with close to 70% of individuals in low-income nations being sedentary during leisure time compared with around 40% in higher-income countries. The message here is simple, says Held. "Try to incorporate your activity into your daily life. Take the stairs, and walk when you can. Don't complicate it."

Try to incorporate your activity into your daily life. Take the stairs, and walk when you can. Don't complicate it.

The results also show an association between ownership of a TV and car and an increased risk of MI, although Held stresses, "We cannot say this is a causal relationship, it's an association, and we need a prospective trial to confirm this." Nevertheless, he acknowledges, "If you own a TV and a car, your risk of being sedentary is increased. It's an interesting finding that goes with the theme."

In an accompanying editorial [2], Drs Emeline M Van Craenenbroeck and Viviane M Conraads (Antwerp University Hospital, Belgium) observe: "Physical activity remains the single most neglected therapeutic intervention worldwide. Staying physically fit throughout life may well be one of the easiest, cheapest, and most effective ways to avoid the coronary care unit."

Mild/Moderate Occupational- and any Leisure-Time Activity Is Protective

In their new look at INTERHEART--a case-control study of over 29 000 people from 52 countries in Asia, Europe, the Middle East, Africa, Australia, and North and South America--Held and colleagues specifically examine how physical activity during work and leisure time contribute to the risk of MI.

They note that although much prior research has found a link between physical activity during leisure time and CV disease, the association with work-related activity is less clear. And few studies have evaluated the different aspects of physical activity both at work and during leisure time in relation to CV risk.

"What this study adds, among many other things, is a global perspective," says Held. It shows that mild to moderate physical activity at work and any level of physical activity during leisure time "reduce the risk of heart attack, independent of other traditional risk factors, in men and women of all ages, in most regions of the world, and in countries with low-, middle-, or high-income levels."

The researchers found that subjects whose occupation involved either light [multivariable adjusted odds ratio 0.78] or moderate [OR 0.89] physical activity were at lower risk of MI, whereas those who did heavy physical labor were not (OR 1.02) compared with sedentary subjects. Mild exercise (OR 0.87) as well as moderate or strenuous exercise (OR 0.76) was also protective. Those who owned both a car and a TV were at higher risk of MI compared with those who owned neither (OR 1.27).

The fact that heavy physical labor at work did not protect against heart attacks is interesting, says Held, who admits he doesn't have a good explanation for this. The editorialists suggest that shift work or psychosocial stress due to being in an undemanding job and having little or no decision-making authority might be counterbalancing the intrinsic beneficial effect of physical activity.

Turning Everyone Danish Is a Herculean Task

The new results "show that we don’t need to have different recommendations for different regions of the world," says Held. "It's easy to reduce the risk of having a heart attack."

In fact, what was somewhat surprising, he says, is that even a small daily duration of exercise seems beneficial. While he does not want to promote the idea that it's good enough to do 15 minutes of exercise a day, he says the findings show that any activity is better than nothing.

The paper of Held et al leaves clinicians with the Herculean task of translating this evidence into effective preventive care.

"Of course, there are cultural differences at play, and climate plays a role," he notes. "If you live in a country with a climate of 35⁰C, you are less likely to be jogging around." But this just reinforces the overall message, which is to try, as much as possible, to incorporate physical activity into daily life, he says.

The editorialists agree: "Ideally, we should adopt the example set by the Danish and commute by bike," they observe.

"Although timely and relevant, the paper of Held et al leaves clinicians with the Herculean task of translating this evidence into effective preventive care," they continue. "If we want to support healthy longevity, we should put a stop to the pandemic of 'sedentarism.' "

Authors and editorialists report no conflicts of interest.