Dec. 13, 2019--The number of people newly infected each year and the number of people living with nontuberculous mycobacterial lung disease appears to be increasing, especially among women and those 65 and older, according to new research published online in the Annals of the American Thoracic Society.
In "Incidence and Prevalence of Nontuberculous Mycobacterial Lung Disease in a Large United States Managed Care Health Plan, 2008-2015," Kevin L. Winthrop, MD, MPH, and colleagues report on their analysis of NTM diagnoses among approximately 27 million participants in a national health care plan (Optum) during the eight-year study period.
"Our findings add to other recent studies from North America and other regions of the world that show NTM disease is increasing," said Dr. Winthrop, professor of infectious diseases and public health at the Oregon Health and Science University.
Nontuberculous mycobacteria (NTM) are found naturally in the environment, and everyone inhales them. The most common NTM is Mycobacterium avium complex, though altogether there are more than 160 different species.
While only a tiny fraction of people develops NTM disease, those with chronic lung diseases such as COPD and cystic fibrosis and those who are immunocompromised are at greater risk for the disease, which can be debilitating and even cause death. Unlike the bacterium that causes tuberculosis, NTM is not contagious.
The researchers reported incidence, the number of new infections reported each year per 100,000 person-years (the number of participants × eight years) and prevalence, the total number of those living with NTM in a given year per 100,000 persons.
The study found from 2008 to 2015:
The annual incidence of NTM lung disease increased from 3.13 to 4.73 per 100,000 person-years.
The annual prevalence increased from 6.78 to 11.70 per 100,000 persons.
For women, the annual incidence increased from 4.16 to 6.69 per 100,000 person-years, while the prevalence increased from 9.63 to 16.78 per 100,000 persons.
For those aged 65 and older, the annual incidence increased from 12.70 to 18.37 per 100,000 person-years, while the annual prevalence increased from 30.27 to 47.48 per 100,000 persons.
The incidence of NTM increased by at least 10 percent in 29 states.
The prevalence of NTM increased by at least 10 percent in 39 states.
"There are likely multiple reasons for these increases," Dr. Winthrop said. "The number of people at risk is increasing because the population is aging and more people are living with chronic lung diseases. Increasing environmental exposure is also likely a factor, as is greater awareness of NTM disease among physicians."
He added that the high rates of NTM among women may be explained by the fact that they live longer and may be more likely to seek medical care. There may also be as yet unidentified biologic and genetic factors that contribute to greater incidence and prevalence among women.
Study limitations include inaccuracies in diagnostic coding and unequal distribution of participants in the health plan across the country.