Aging or comorbid conditions - what is the main cause of kidney damage?

BACKGROUND: Chronic kidney disease (CKD) is widespread in the general population. It is generally accepted that worsening renal function is common with aging. However, the question still remains whether it is caused by the natural process of aging or whether coexisting chronic diseases and comorbid conditions contribute to deteriorating renal function.
METHODS: The frequency of albuminuria-the marker of early kidney damage-was evaluated according to different coexisting conditions in younger (18/64 years old, n=2,074) and elderly (=65 years old, n=395) participants of the Polish study PolNef on early detection of CKD. Multivariate logistic regression was performed to identify associations between elevated levels of albuminuria, age and coexisting conditions.
RESULTS: 12% of the younger group demonstrated albuminuria compared to 18% of the elderly. Independent predictors of detecting an elevated level of albuminuria for the whole examined population were male gender (2.48, 1.59-3.88), hypertension ineffectively treated (1.8, 1.34-2.4), diabetes (1.67, 1.11-2.49), and age (1.56, 0.97-2.52) at border levels of significance. Moreover, elevated levels of albuminuria occurred more frequently in the obese elderly group (1.89, 0.98-3.63, p=0.058). The following predictors were found based on gender: for men, hypertension regardless of efficacy of treatment, diabetes, smoking, and age at border level of significance, in contrast to women who had the sole predictor of ineffectively treated hypertension.
CONCLUSIONS: The influence of aging alone on kidney damage is not evident. Moreover, it is different in males and females. Hypertension is the only coexisting comorbid condition contributing to kidney damage in both males and females. Advanced age together with comorbid conditions is more harmful to the kidney in males.