Heterogeneity of clinical indices among the older dialysis population—a study on Japanese dialysis population

The older dialysis population is increasing, and several studies have investigated the effect of actual age on the relationship between clinical parameters or clinical practice and prognosis. There is concern that biological age does not necessarily reflect the actual effects of aging, and it is important to take heterogeneity into account when considering the older population. In this study, we investigated whether such heterogeneities exist in a large number of clinical parameters and how any disparities might be affected by the domains of clinical indices. We investigated the published, summarized results of the Japanese Society for Dialysis Therapy Renal Data Registry, a nationwide survey of the Japanese dialysis population, for the year 2013. The potential population comprised 306,925 dialysis patients. We investigated coefficient of variations (CVs) of 25 clinical indices across age groups and compared them with the CVs of the 45–59 years age group as a reference group, using tests for homogeneity of variances. Almost all variables showed some heterogeneity by age. The domain for muscle mass or visceral protein exhibited greater heterogeneity in older patients, but surprisingly, the domain for body mass or physique exhibited less heterogeneity. The mean values of most parameters declined in the older population. This study demonstrated that variations exist in clinical indices in the older dialysis population. Apart from biological age, we should take these heterogeneities into account when interpreting the findings of clinical studies involving older dialysis patients and in their individualized management.