Men were more than twice as likely to have COPD as women. But while smoking was, and is, a significant risk factor for COPD in China, only 24% of the females with COPD were smokers, as opposed to nearly 82% of males, suggesting that women's risk might be more strongly associated with the use of biomass fuels, especially for cooking in poorly ventilated areas.
"Although China has experienced remarkable modernization over the past two decades, in many rural areas residents continue to use wood, charcoal or coal for fuel, leading to significant biomass exposure, especially in women, who perform most of the cooking duties," wrote Don D. Sin, M.D., and Wan Tan, M.D., of the University of British Columbia in Vancouver, Canada, in an editorial in the same issue of the journal.
"To the best of our knowledge, this is the first large-scale, population-based epidemiologic study on COPD prevalence in China," wrote Nanshan Zhong, M.D., of the Guangzhou Institute of Respiratory Diseases at The First Affiliated Hospital in Guangzhou Medical College, and lead researcher.
According to an estimation by the World Health Organization, COPD ranks first among the burdens of diseases in China and accounts for one million deaths and five million disabilities each year.
The researchers selected provinces and cities from a wide range of geographic areas within China, and then selected an urban and a rural area within each province/city. They then used randomized cluster sampling from a randomly selected street or township, and attempted to recruit all individuals older than 40. About 79% of attempted were successfully contacted. They completed questionnaires and underwent spirometric testing for obstructive and restrictive lung disease.
While the overall rate of COPD, as defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) was higher than expected, there were some notable differences among the population.
"Multivariate logistic regression analyses showed that smoking, pulmonary problems in childhood, family history of respiratory diseases, male sex, low education level, aging, lower body mass index, poor ventilation in the kitchen, and exposure to biomass and occupational dust/gases/fumes are associated with COPD," wrote Dr. Zhong.
Importantly, more than a third of the subjects who had COPD were asymptomatic, and nearly two-thirds had never been diagnosed, suggesting that diagnosis of COPD on symptoms alone is not sufficient.
"Even among subjects with GOLD stages 3 and 4 of the disease, fewer than 10% have ever received spirometry," noted Drs. Sin and Tan. "The gross underutilization of spirometry represents a 'Great Wall,' a huge barrier to good care for patients with COPD in China."
Dr. Zhong and colleagues' findings present a dark picture of COPD in China, which is expected to grow worse before it gets better due to an aging population and rising smoking rates, especially in women.