Asthma significantly increases the risk of invasive pneumococcal disease, according to results of a recently published study. Investigators examined this association in persons between 2 and 49 years old who were enrolled in Tennessee's Medicaid program for more than one of the eight years of the study period and who lived in a county covered by surveillance for bacterial disease. For each subject who developed invasive pneumococcal disease, investigators randomly selected 10 age-matched controls without disease. For all subjects and controls, investigators examined data about the presence of asthma and coexisting conditions associated with a high risk of pneumococcal disease (HIV infection, sickle cell disease, diabetes mellitus, cardiac disease, renal disease, hepatic disease, obstructive pulmonary disease, alcohol abuse, tobacco use).
From 1995 through 2002, investigators identified 635 people with invasive pneumococcal disease and enrolled 6,350 controls. Of those with invasive pneumococcal disease, 114 (18%) had asthma, compared with 516 (8.1%) of controls. Subjects with pneumococcal disease were significantly more likely than controls to be male and black. Those with the disease also were more likely to have previously recognized coexisting conditions associated with increased risk of pneumococcal disease. In addition, compared with controls with asthma, case subjects with asthma were more likely to have high-risk asthma (rather than low-risk asthma); more likely to have been hospitalized for asthma within the previous year; and more likely to have received long-term oral corticosteroid therapy. Even after adjusting for other high-risk conditions, patients with asthma had an increased risk of invasive pneumococcal disease (odds ratio, 2.4).
During the study period, the average annual incidence of invasive pneumococcal disease in the study population was 6.1 episodes for every 10,000 people with asthma, compared with 2.0 episodes for every 10,000 nonasthmatics. The annual incidence of invasive pneumococcal disease among those with high-risk asthma (i.e., requiring admission to a hospital or visit to an emergency room, use of rescue therapy or long-term use of oral corticosteroids, or requiring dispensing of three or more prescriptions for a β-agonist within the preceding year) was 6.0 episodes; among those with low-risk asthma, 3.9 episodes. For patients with no other high-risk coexisting conditions, the annual incidence of invasive pneumococcal disease still was higher among those with asthma than in those without it: 4.2 episodes for every 10,000 people with high-risk asthma and 2.3 episodes for every 10,000 with low-risk asthma (Talbot TR et al: N Engl J Med 2005;352:2082).