Background: Chronic kidney disease (CKD) is a growing public health problem with well-established risk factors. Other contributing factors, however, remain to be identified. Systemic inflammation in asthma plays a significant role in the development of other diseases. We therefore initiated a study to assess whether the growing prevalence of asthma is associated with an increase in the risk of CKD.
Methods: We conducted a retrospective cohort study using data from 3015 patients with asthma aged 14 years and older who were registered and followed up in Asthma Control Study at the Department of Respiratory Medicine of three medical centers from 2005 to 2011. History, asthma control test (ACT), and asthma stage were used to assess the traits of asthma. CKD was defined as proteinuria and/or reduced estimated glomerular filtration rate (eGFR) (<60 ml×min(-1)×1.73 m(-2)) in two consecutive follow-up surveys. We used logistic regression models, adjusting for age, sex, and other confounding factor to determine associations between the traits of asthma and CKD. Kaplan-Meier curves were used to analyze patient outcomes.
Results: A total of 2354 subjects with complete data were recruited for this study with mean age (45.4±10.4) years. After 6 years of follow-up, 9.6% (n = 227) of the analytic cohort developed proteinuria and 3.1% (n = 72) progressed to eGFR <60 ml×min(-1)×1.73 m(-2). The patients with >20 years asthma history, not well-controlled or persistent asthma patients had higher incidence of proteinuria and reduced eGFR compared with patients with ≤20 years asthma history, at least well-controlled or remission asthma, respectively. The multivariable adjusted OR for proteinuria and reduced eGFR in participants with persistent asthma was 1.49; (95% confidence interval (CI) 1.17-1.91) and 2.07 (95% CI 1.34-4.42). Compared to patients with no asthma traits, there was a significant risk (OR, 3.39; 95% CI 1.36-8.73) for those who met all three traits, including asthma history >20 years, not well-controlled and persistent stage, after adjusting for potential confounding factors.
Conclusions: In this retrospective cohort study, we found that persistent asthma was associated with an increased risk of CKD, which was independent of obesity, diabetes, hypertension, and other well-established risk factors. Future studies should be directed to elucidate the mechanisms underlying the association between asthma and CKD.