THURSDAY, Sept. 8, 2016 (HealthDay News) -- Fewer Americans are dying from chronic obstructive pulmonary disease (COPD), but not black women and the middle-aged, a new government report shows.

Between 2000 and 2014, there was a 12 percent overall drop in deaths from the progressive lung disease, according to the U.S. Centers for Disease Control and Prevention.

Report co-author Hanyu Ni said the figures aren't unexpected, noting that "the declines in the COPD-related mortality are consistent with declines in the prevalence of current smoking for men and women in the United States."

But, Ni added, the study only quantified death rate trends, and didn't look at the reasons behind those trends. Ni is an associate director for science with the CDC's division of vital statistics at the U.S. National Center for Health Statistics.

Dr. David Mannino, who's with the University of Kentucky's College of Public Health, agreed that the study "results are not surprising." He, too, cited the nationwide decline in smoking, the number one cause of COPD.

"Smoking is the biggest factor driving COPD deaths in the U.S.," said Mannino, a professor of medicine in the division of pulmonary, critical care and sleep medicine.

Chronic obstructive pulmonary disease is a progressive disease of the airways that makes it difficult to breathe. COPD includes emphysema and chronic bronchitis. It's the third biggest killer in the United States, and most people with COPD are current or past smokers, according to the U.S. National Heart, Lung, and Blood Institute.

For the study, Ni's team reviewed data collected by the National Vital Statistics System between 2000 and 2014.

The report painted a mixed picture of risk.

For example, while men saw their COPD fatality rate drop by nearly 23 percent, women saw their rate fall by just 4 percent.

Age also played a role. Men between the ages of 65 and 84 saw their death rate drop by nearly 30 percent, while those 85 and older saw their rate dip by 23 percent. But for men between 45 and 64, the death rate rose by nearly 13 percent.