Tiago Villanueva: The global burden of physical inactivity on health

tiago_villanuevaThe World Cup is now here, but for many of us that just means we will be watching the matches from our couch at home, or, if you’re one of the lucky ones, from the stands in Brazil’s stadiums. Ironically, such a high profile sporting event will foster sedentary behaviour in a lot of us, by making us sit in front of the television for countless hours, especially if our team goes far in the competition.

I recently had the chance to listen to Dr Pedro Hallal—a Brazilian academic and researcher from the Federal University of Pelotas—give a talk in Central London, which was organised by C3 Collaborating for Health. Hallal discussed his research into the effects of physical inactivity on major non-communicable diseases; of which a great deal has been published in several Lancet series, most recently this one on physical activity in 2012.

Hallal highlighted that physical inactivity may be responsible for causing around 5.3 million deaths each year—more than smoking, which he estimates has the potential to cause around 5.1 million deaths each year. Even though smoking carries a greater risk than physical inactivity of harming your health at an individual level, physical inactivity is more harmful at a population level, because so many more people are physically inactive. In fact, about half of Brazil’s population is considered physically inactive—defined here as engaging in less than 150 minutes of moderate intensity, aerobic activity each week. In contrast, hypertension affects 30% of the population, 18% of the population smokes, 17% of the population is obese, 9% of the population has diabetes, and 1% has HIV.

He added that, in total, about one third of adults, and four fifths of adolescents (aged 13 to 15), do not achieve guidelines’ recommended level of physical activity. Even though that means 150 minutes of physical activity each week for adults, as previously mentioned, the figure goes up to one hour every day for adolescents.

But we need to look beyond the surface of these statistics, and take them with a grain of salt. Hallal, whose PhD paper was published in The BMJ, actually considers this definition for adolescents to be too strict, as it implies that an adolescent who engages in physical activity six days a week is still physically inactive.

It doesn’t help that over 90% of the evidence available on the effects of physical activity interventions comes from high income countries, even though most of the target population lives in the developing world, where there are no interventions. Hallal gave the example of snake bites in Brazil. Most of the areas in Brazil with snake populations lack statistical information on this, so we don’t know what’s really happening. But, in areas that do generate statistical information, there are no snakes.

Decreasing the burden of physical inactivity by 10% or 25% could avoid around half a million deaths or 1.3 million deaths, respectively, each year. One problem Hallal highlighted is that physical activity is not high enough on the agenda of researchers and policy makers. So physical activity needs to be prioritised, but for the time being, the World Cup will call for some more sedentary behaviour.

Tiago Villanueva is the editorial registrar at The BMJ.