The team decided to investigate lifetime risk because there's an "under-recognition" of chronic obstructive pulmonary disease as a public health issue and its effect on millions of Canadians, said principal investigator Dr. Andrea Gershon.
For instance, there are few fundraisers or walks to raise awareness for COPD, said Gershon, a scientist at the Institute for Clinical Evaluative Sciences and a respirologist at Sunnybrook Health Sciences Centre.
"It's the fourth leading cause of death in Canada — it comes after cancer, heart disease and stroke. In the States, COPD just surpassed stroke, and I'm going to guess that in Canada next time they release the stats it will too."
The risk of developing the disease by age 80 was 29.7 per cent for men, and 25.6 per cent for women, according to the study, published this week in the prestigious medical journal The Lancet.
Gershon said this one-in-four risk is comparable to that of getting diabetes or asthma, about double the risk of getting congestive heart failure, and about triple that of heart attacks, breast cancer in women and prostate cancer in men.
Although smoking is the No. 1 risk factor for COPD, she said health-care professionals are also seeing other factors, including aging, occupational exposures to fumes or dust, and a link with childhood respiratory problems.
For the study, researchers used health administrative data and followed people aged 35 to 80 who didn't have COPD in 1996 for the next 14 years. A total of 579,466 cases were identified over the study period.
"We can basically extrapolate from that data to determine what the entire lifetime risk of developing COPD is," Gershon said, noting that lifetime risk of getting the disease is a different measure than prevalence, which an earlier study found was 9.5 per cent in 2007. Prevalence measures how much of a disease is in a population at a particular point in time.
The study found that lifetime risk was higher for those of lower socioeconomic status than for wealthier Ontarians, for rural residents compared to urbanites, and for men compared to women.
"We looked at 35 and older because children don't get COPD," explained Gershon.
"It's really a disease of aging — older people are more likely to get the disease, but it's also a disease of cumulative exposures. It's a chronic disease. You kind of have to have something going on for a while, usually smoking, before you develop it."
Dr. Darcy Marciniuk, a member of the COPD committee of the Canadian Thoracic Society, said the study results confirm clinical suspicions and validate the large number of patients that are being seen in clinical practices.
"This is yet another piece of fairly convincing evidence that suggests that there is a significant disease burden," he said from Saskatoon, where he is a professor of medicine at the University of Saskatchewan.
"I think the results certainly have implications in terms of our priorities and funding in the areas of clinical care delivery and research. It also speaks to, with this growing burden, the importance of targeted testing for early detection."
Gershon said it appears that attention is often lacking for COPD because people tend to blame patients for smoking. But she said other diseases with a higher profile, such as heart disease and stroke, are linked to smoking as well.
"Smoking is an addiction. It's not easy to quit smoking and, you know, just to dismiss them because they're smokers really isn't solving any problems or helping any people," she said.
Second-hand smoke and other exposures could be contributing, she noted, adding that COPD is the No. 1 cause of chronic disease hospitalization in Canada.
"So people with COPD need hospital beds, they need emergency department visits, they need and they end up using a lot of resources," she said.
"And if we can help them, which is what we want to do, we can also decrease this stress on the health-care system and everybody will benefit."
The findings can be used to justify the continuation and expansion of smoking cessation programs, the researchers said.
Kimberlyn McGrail, associate director of the Centre for Health Services and Policy Research at the University of British Columbia, indicated that it's useful for health-care administrators to know more about COPD patients hitting the system.
"Then you can get into saying, 'OK, are they actually needing to use the hospital as often as they do?'" she said from St. Andrews, Scotland, where she was attending a conference.
"Not saying that we should keep people out when they actually need acute care services, but if we reorganize primary care, if there were other things that were done in the community, could we help people not use so many services and not get to those crisis points?"
A related commentary in The Lancet by David Mannino of the University of Kentucky and Fernando Martinez of the University of Michigan Health System said that cross-sectional studies of adults with COPD suggest that asthma is a risk factor for developing COPD.
"Future rates of COPD (caused by increased asthma rates) might be higher than they are now, even if smoking rates continue to fall," they wrote. "However, better interventions for asthma, such as the use of inhaled steroids to treat inflammation, could result in less airway remodelling and, subsequently, less COPD."