Researchers say that the number of people newly infected each year and the number of people living with nontuberculous mycobacterial (NTM) lung disease seems to be increasing, especially among women and persons age 65 and older.
In “Incidence and Prevalence of Nontuberculous Mycobacterial Lung Disease in a Large United States Managed Care Health Plan, 2008-2015,” published in an online article published in the Annals of the American Thoracic Society.
In the research study, Kevin L. Winthrop, MD, MPH, and colleagues reported on their analysis of NTM diagnoses among approximately 27 million enrolled in a national health care plan (Optum) during the eight-year study period.
NTM Disease is Increasing
“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 in a Dec. 13 statement announcing the study’s findings.
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, say the researchers.
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, say the researchers, noting that NTM 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 while the annual prevalence increased from 6.78 to 11.70 per 100,000 persons.
According to the study’s findings, 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 age 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.
As to geographical location, the incidence of NTM increased by at least 10 percent in 29 states and the prevalence of NTM increased by at least 10 percent in 39 states.
Dr. Winthrop notes that “There are likely multiple reasons for these increases,” noting that 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 says.
Higher Rates of NTM Among Women
The Oregon Health and Science University researcher believes 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,” he adds.
Study limitations include inaccuracies in diagnostic coding and unequal distribution of participants in the health plan across the country, says Dr. Winthrop.