Incremental Mortality Associated with Nontuberculous Mycobacterial Lung Disease Among US Medicare Beneficiaries with Chronic Obstructive Pulmonary Disease

RATIONALE Nontuberculous mycobacterial lung disease (NTMLD) is an uncommon mycobacterial infection whose prevalence has increased over the last decade. Many patients with NTMLD have comorbid respiratory diseases such as COPD. Treatment of NTMLD in patients with COPD may receive inadequate attention as COPD and NTMLD share common symptoms such as cough and dyspnea and clinicians often prioritize on symptoms management. There is a lack of data quantifying the incremental mortality burden that NTMLD adds to existing COPD. We assessed this incremental burden of NTMLD in patients with COPD by comparing their mortality to that of matched COPD patients without NTMLD. METHODS A retrospective cohort study was conducted using the US Medicare claims database (2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017). COPD patients with NTMLD (cases) were matched 1:3 to COPD patients without NTMLD (controls) by age and sex; the index date (date of the first NTMLD diagnosis) of each case was assigned to the matched controls. Mortality records were identified over the post-index follow-up until data cutoff or death. Incremental mortality of NTMLD was assessed with the annual mortality rate and time to death using univariate and multivariate analyses adjusting for demographics, comorbidities, and severity of COPD (count of hospitalization and ER visits with COPD as primary diagnosis, supplemental oxygen therapy and duration of COPD) during 12-month pre-index period. RESULTS A total of 4,926 cases were matched to 14,778 controls. The mean (SD) follow-up in years post-index was 2.62 (1.71) and 3.10 (1.78) for cases and controls respectively. In univariate analyses, higher proportion of COPD patients with NTMLD had died during follow-up compared to controls (41.5% vs 26.7%; P<0.0001); the annual mortality rates were higher among patients with NTMLD (158.5 vs 86.0 deaths per 1000 person-years); time to death (Figure vs 3.40 (95% CI, 3.27-3.53) years when 25% of patients had died. This incremental mortality risk was also reflected in subsequent multivariate analyses after adjusting for confounding factors: the mortality rate ratio associated with NTMLD was 1.44 (95% CI, 1.35-1.53; P<0.0001); the hazard ratio associated with NTMLD was 1.45 (95% CI, 1.36-1.54; P<0.0001). CONCLUSIONS COPD patients with NTMLD have a higher mortality compared to COPD patients without NTMLD. These findings suggest the substantial incremental deaths associated with NTMLD adds to existing COPD and highlight the acute need for appropriate management of NTMLD in this patient population.

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