Obesity is set to overtake smoking as the most common risk factor for heart disease in Canada next year, a new study suggests.

Heart disease is a leading cause of death in this country, killing more than 70,000 people a year.

The study in Tuesday’s issue of CMAJ Open used a new model to estimate cardiovascular risk based on the lives of 22.5 million simulated Canadians aged 20 years and older.

hi-obesity-waist-852-cp-585

Is obesity more of a marker of problems in broader society than a risk factor? (Howie McCormick/Associated Press)

"The most interesting finding for us is this idea that obesity looks like it's going to continue to increase and smoking looks like it's going to continue to decrease. That's going to play out in heart disease," lead author Dr. Doug Manuel, a senior scientist at the Ottawa Hospital Research Institute, said in an interview.

"When we first plotted out the numbers, we saw this big X where smoking crosses over obesity and obesity becomes the most common cardiovascular risk factor."

To build the model, the researchers used:

  • Population factors such as age, sex, socioeconomic position and province.
  • Changes over time from births, deaths, immigration and emigration.
  • Cardiovascular risk factors such as blood pressure, high cholesterol, body mass index diabetes and smoking figures from the Canadian Health Measures Survey.

The good news, if the model holds up to reality, is that the rate of heart disease is set to decline in Canada, especially as more people quit smoking — the most hazardous risk factor for heart disease.

Better control of blood pressure is also forecast to help.

But obesity affects nearly one in five adults. Higher rates of diabetes also threaten to counteract the gains and diabetes is almost as strong a risk factor for heart disease as smoking, said Manuel, a public health physician.  

For cardiologists and population health experts, it’s difficult to make predictions about what will happen with heart disease rates since there are so many factors.

Big picture on food and exercise

A journal commentary published with the study said while the analysis considered some of the main risk factors, others such as excessive alcohol consumption or low intake of fruit and vegetables, were omitted.

"Obesity may, arguably, be more of a marker of problems in the broader society than a direct cause or risk factor," wrote Garry Egger of the School of Health and Human Sciences at Southern Cross University in New South Wales, Australia.

"Big picture" concerns, such as quality and affordability of food, conduciveness to exercise and environmental contaminants are often the result of political, economic and social policies that are rarely considered in such clinical research, Egger said.

Manuel suggested policymakers could use the model as a baseline to estimate how changes, such as improving food affordability, could affect health behaviours.

The study was funded by the Canadian Institutes of Health Research.

With files from CBC's Amina Zafar