Chronic obstructive pulmonary disease (COPD) is associated with an increased risk for death among patients with chronic kidney disease (CKD), new findings suggest. The association is more pronounced in younger patients and women.

In a study that included 56,960 patients with stages 3 and 4 CKD, researchers led by Sankar D. Navaneethan, MD, MS, MPH, of the Baylor College of Medicine in Houston, found that the presence COPD was associated with a 41% increased risk for all-cause mortality and a 4-fold increased risk for respiratory-related deaths after adjusting for potentially confounding variables.

“These data highlight the need for further prospective studies to understand the underlying mechanisms and potential interventions to improve outcomes in this population,” the authors concluded in a paper published in the American Journal of Nephrology (2016;43:39-46).

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Of the 56,960 patients, 2,667 (4.7%) had underlying COPD. During a median follow-up of 3.7 years, 15,969 patients died. The mean ages of the patients with and without COPD were 74.6 and 72.2 years, respectively.

Factors found to be significantly associated with having COPD include older age, diabetes, coronary artery disease (CAD), congestive heart failure (CHF), hypertension, and smoking. Each 10-year increment in age was associated with 26% increased odds of having COPD. Diabetics had a 19% increased odds compared with non-diabetics. Patients with CAD, CHF, and hypertension had 1.6, 2.3, and 3.0 times increased odds, respectively, compared with patients without these conditions. Smokers had a 2.9 times increased odds compared with non-smokers.

Given their lack of spirometry data, the COPD prevalence found in the new study probably is an underestimate, according to the investigators. They pointed out that even in the general population, COPD is underdiagnosed, with about 63% of adults showing evidence of impaired lung function but do not have a diagnosis of lung disease such as asthma, chronic bronchitis, or emphysema.

The effect of COPD on mortality differed by age and gender. In adjusted analyses, COPD was associated with a 2-fold increased risk of death among patients aged 45–60 years and 62%, 35% and 28% increased risk among those aged 61–70, 71–80, and 81 years or older, respectively.

“It appears that with aging, the effect of COPD on outcomes become less relevant in those with CKD,” Dr. Navaneethan’s team commented.

COPD in male and female patients was associated with a 29% and 55% increased risk of death, respectively.

As for possible explanations for the increased risk for overall mortality and respiratory deaths among CKD patients, Dr Navaneethan and colleagues pointed out that “higher infection-related deaths, especially with pneumonia, have been reported in the CKD population.” The additional presence of COPD, they noted, could further increase the risk for pneumonia or other infection due to immunosuppression from long-term use of COPD medications. Further, they stated that “COPD is a known contributor to pulmonary hypertension and could contribute to adverse outcomes in CKD.”