Ambient carbon monoxide correlates with mortality risk of hemodialysis patients: comparing results of control selection in the case-crossover designs

Abstract

Background: Growing evidence suggests that environmental air pollution adversely affects kidney health. To date, the association between carbon monoxide (CO) and mortality in patients with end-stage renal disease (ESRD) has not been examined. Methods: Among 134,478 dialysis patients in the Korean ESRD cohort between 2001 and 2014, 8,130 deceased hemodialysis patients were enrolled, and data were analyzed using bidirectional, unidirectional, and time-stratified case-crossover design. We examined the association between short-term CO concentration and mortality in patients with ESRD. We used a two-pollutant model, adjusted for temperature as a climate factor and for nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and particulate matter less than 10 μm in diameter as air pollution variables other than CO. Results: Characteristics of the study population included age (66.2 ± 12.1 years), sex (male, 59.1%; female, 40.9%), and comorbidities (diabetes, 55.6%; hypertension, 14.4%). Concentration of CO was significantly associated with all-cause mortality in the three case-crossover designs using the two-pollutant model adjusted for SO2. Patients with diabetes or age older than 75 years had a higher risk of mortality than patients without diabetes or those younger than 75 years. Conclusion: Findings presented here suggest that higher CO concentration is correlated with increased all-cause mortality in hemodialysis patients, especially in older high-risk patients.

Clearing the air: a review of the effects of air pollution on dialysis outcomes

“…Individuals with diabetes and older age >75 years had higher mortality after CO exposure [27]. Patients with anemia (hemoglobin < 10 mg/dl) had an increased risk of mortality after CO exposure (bidirectional OR: 1.57 [95% CI: 1.12, 2.22] and time-stratified OR: 1.49 [95% CI: 1.03, 2.15]) [27]. Blood pressure or dialysis adequacy did not significantly affect odds of mortality [27].…”

“…We identified five studies (n ¼ 5) which evaluated the effects of carbon monoxide on mortality [27], cardiovascular disease risk (assessed as baPWV) [23], inflammation [28], and other complications of ESKD [29,30] (Table 2).…”

“…Ambient exposure to CO is associated with mortality in the general population including patients with ESKD [31,32]. In this review, we identified a single study (n ¼ 1) that reported associations between CO exposure among dialysis patients and mortality using a case crossover study design with 8130 deceased HD patients from the Kidney Dialysis Registry database of the Korean Society of Nephrology [27]. Air pollutant data was obtained from the Korean National Institute of Environmental Research from 89 monitoring sites located in 7 cities [27].…”

“…Air pollutant data was obtained from the Korean National Institute of Environmental Research from 89 monitoring sites located in 7 cities [27]. In 3 of the cities, CO concentrations were found above the 90th percentile at 1.002 ppm, 1.025 ppm, and 1.096 ppm [27]. Three case crossover models (bidirectional, unidirectional, and time-stratified designs) were used to reduce the influence of unmeasured confounding [27].…”

“…The single pollutant model identified positive associations with CO and all-cause mortality (bidirectional OR: 1.20 [95% CI: 1.04, 1.39]; unidirectional OR: 1.45 [95% CI: 0.95, 1.38]; and time-stratified OR: 1.19 [95% CI: 1.02, 1.38]) [27]. Individuals with diabetes and older age >75 years had higher mortality after CO exposure [27]. Patients with anemia (hemoglobin < 10 mg/dl) had an increased risk of mortality after CO exposure (bidirectional OR: 1.57 [95% CI: 1.12, 2.22] and time-stratified OR: 1.49 [95% CI: 1.03, 2.15]) [27].…”