Asthmatics face high cancer risk

The risk of developing cancer appears to be elevated among people with asthma, reports a recent study.

Researchers drew from two independent, population-based, longitudinal Korean cohorts: the National Health Insurance Service-National Sample Cohort (NHIS-NSC), an unmatched sample including n=475,197 participants; and the Ansan-Ansung cohort, which included 5,440 participants.

After propensity score matching, the NHIS-NSC cohort shrunk down to 75,307 participants, of whom 6,885 had asthma and 68,442 did not. Over the mean follow-up of 7.60±3.74 years, 3,687 incident cases of cancer were recorded, 549 of which occurred in participants who had newly diagnosed asthma.

The corresponding cancer incidence rates in those with vs without asthma were 10.69 and 6.02 per 1,000 person-years. In Cox proportional hazards regression analyses, this resulted to a 75-percent increase in cancer risk after full adjustments for confounders (adjusted hazard ratio [HR], 1.75, 95 percent confidence interval [CI], 1.58–1.94).

Competing risk analysis of mortality slightly weakened the impact of asthma, but did not completely attenuate it (adjusted HR, 1.62, 95 percent CI, 1.47–1.80).

Stratifying according to time of asthma diagnosis, the researchers found that cancer risk was highest >5 years after asthma diagnosis (adjusted HR, 2.01, 95 percent CI, 1.66–2.45), but nevertheless remained significantly elevated within 3 years (adjusted HR, 1.64, 95 percent CI, 1.44–1.87) and 3–5 years (adjusted HR, 1.81, 95 percent CI, 1.50–2.20) after diagnosis.

Notably, the researchers also saw that a high cumulative dose of inhaled corticosteroids exerted a significantly protective effect against lung cancer (adjusted HR, 0.44, 95 percent CI, 0.29–0.67), but not on the overall risk of developing any malignancy (adjusted HR, 0.84, 95 percent CI, 0.70–1.02).

Analyses using data from the Ansan-Ansung cohort were consistent with the principal findings from the NHIS-NSC cohort.