Two-fold risk of pneumonia and respiratory mortality in individuals with myeloproliferative neoplasm: A population-based cohort study

BACKGROUND: High cardiovascular comorbidity contributes to excess mortality in patients with myeloproliferative neoplasm, while less is known about respiratory comorbidity and mortality. We tested the hypothesis that individuals with myeloproliferative neoplasm have increased risk of pneumonia and respiratory mortality. METHODS: Of 249 294 invited individuals aged ≥20 from the Danish general population from 2003–2015, 107 900 participated and were included in the Copenhagen General Population Study (response-rate: 43%). We examined lung function and respiratory symptoms at baseline examination and followed individuals prospectively from baseline examination through 2018 to determine risk of pneumonia and respiratory mortality using Cox proportional hazard regression. Among 351 individuals with myeloproliferative neoplasm, 131 (37%) were diagnosed at baseline examination and 220 (63%) were diagnosed during follow-up. The follow-up cases were entered in the regression analysis by using a time-varying variable. FINDINGS: In total, 125 (36%) individuals had essential thrombocythaemia, 124 (35%) had polycythaemia vera, and 102 (29%) had myelofibrosis/unclassifiable myeloproliferative neoplasm. During follow-up we observed 5979 pneumonias and 2278 respiratory deaths. Compared to individuals without myeloproliferative neoplasm, multivariable adjusted hazard ratios in individuals with myeloproliferative neoplasm were 2·18 (95% CI: 1·60-2·96) for pneumonia and 2·27 (1·46-3·53) for respiratory mortality. Corresponding hazard ratios were 1·26 (0·71-2·30) and 0·96 (0·31-2·94) for essential thrombocythaemia, 2·50 (1·57-3·98) and 3·58 (1·94-6·59) for polycythaemia vera, and 3·03 (1·86-4·93) and 2·40 (1·11-5·19) for myelofibrosis/unclassifiable myeloproliferative neoplasm, respectively. Results were similar in those with and without airflow limitation, and in never-smokers and ever-smokers separately. INTERPRETATION: Individuals with myeloproliferative neoplasm had two-fold increased risk of pneumonia and respiratory mortality, mainly due to polycythaemia vera and myelofibrosis/unclassifiable myeloproliferative neoplasm. These are novel findings.