Per-Ola Sundin, Ruzan Udumyan, Katja Fall, Scott Montgomery

Although acute onset kidney complications associated with severe infections including pneumonia are well characterized, little is known about possible subsequent delayed risk of chronic kidney disease (CKD). Associations between hospital admission with pneumonia in adulthood and raised risks of subsequent CKD were evaluated in a cohort of all male residents in Sweden born from 1952 to 1956 (n=284,198) who attended mandatory military conscription examinations in late adolescence (n=264,951) and were followed up through 2009. CKD and pneumonia were identified using Swedish national registers, and their associations were evaluated using Cox regression. Excluding the first year, the subsequent period was divided into ≤5, >5-≤15, and >15 years after hospital admission with pneumonia. Follow-up ended on the date of first incident diagnosis of kidney disease, death, emigration, or December 31,2009, whichever occurred first. During a median follow-up of 36.7 (interquartile range 35.3-37.9) years from late adolescence, 5,822 men had an inpatient pneumonia diagnosis without contemporaneous kidney disease. Among exposed men, 136 (2.3%) were later diagnosed with CKD compared with 2,749 (1.2%) of the unexposed. The adjusted hazard ratio for CKD in the first year after the first episode of pneumonia was 14.55 (95% confidence interval, 10.41-20.32), identifying early onset kidney complications and possibly pre-existing undiagnosed CKD. Starting follow-up 1 year after pneumonia to reduce the potential influence of surveillance bias and the risk of reverse causation, the adjusted hazard ratio for CKD in the first 5 years of follow-up was 5.20 (95% confidence interval, 3.91-6.93) and then attenuated with increasing time. Pneumonia among inpatients is associated with a persistently increased risk for subsequent CKD, with the highest risk during the years immediately after pneumonia. Health care professionals should be aware of this period of heightened risk to facilitate early diagnosis and secondary preventive interventions.