#1942 Social deprivation and chronic kidney disease: a population based cohort study in Italy
Authors: Giaccari Marta , Marino Claudia , Ferraro Pietro Manuel , Cesaroni Giulia , Davoli Marina , Agabiti Nera 
Published: May 2024

Abstract

Background and Aims
The impact of social deprivation on the progression of Chronic Kidney Disease (CKD) to End Stage Kidney Disease (ESKD) requiring Renal Replacement Therapies (RRTs) and death has been demonstrated by large cohort studies produced both in the US and the UK. Nonetheless, there is still insufficient evidence, which might depend on the difficulty of comparing Health Care Systems from different countries, the lack of a standardized measure of social deprivation and the difficulty of obtaining follow-ups long enough to intercept all clinical outcomes.
This study aims to fill this gap by analyzing a large cohort of patients affected by CKD identified in Healthcare Electronic Records through a validated algorithm.

Method
The study population consisted of all adult incident CKD cases treated conservatively, residents in the Lazio Region, that occurred between the 1st of January 2012 and the 31st of December 2021. The exposure was the deprivation index (DI), a composite indicator at the census block level, which integrates many aspects: low level of education, unemployment, non-home ownership, one parent family and overcrowding. The DI divided the Lazio residents in 5 classes according to the quintiles of its distribution (form very low to very high deprivation). The study outcomes were all-cause mortality and ESKD. The health status of CKD patients was characterized using the hospital discharges for hypertension, heart failure, diabetes, ischemic cardiopathy, obesity and other conditions, in the two years before the identification. Patients were followed form the incident date up to the date of death, ESKD, emigration from Lazio region or 31/12/2022, whichever came first. Cox regression analyses were performed to study the association between DI and adverse outcomes, estimating crude and adjusted Hazard Ratios (HR) and 95% Confidence Intervals (95% CI). The interaction between DI and sex was tested.

Results
From 2012 to 2021, there were 127 457 new CKD cases, 55.9% males. The average age was 72.2 (±13.7 SD) for males and 74.4 (±14.8 SD) for females, characteristics by deprivation index are reported in Table 1. During the follow-up, on average 4.3 years (±3.2 SD), 57 158 patients (45%) died and 5994 developed ESKD requiring RRTs (5%). The mortality analysis showed a statistically significant interaction between DI and sex. In males, there was a strong association between DI and mortality in both age-adjusted and fully-adjusted models (Fig. 1A), with a statistically significant trend across DI classes. In females, there was an association with a statistically significant trend across DI categories but the only statistically significant different HR was very high DI VS. very low DI (HR = 1.05; 95% CI = 1.00-1.09) (Fig. 1B). The association was much stronger for males then for females. In the ESKD outcome analysis there was not an interaction between sex and DI; hence, sex was used as confounder. The age-adjusted HR and the fully-adjusted HR of DI on ESKD did not show any trend across the DI categories and then the low and medium deprived had a lower ESKD risk compared to the very deprived.

Conclusion
The present study is so far the largest European prospective cohort regarding the association between socioeconomic position and CKD. The HR of mortality was inferior to the one found in the UK studies (HR 1.6). The most likely explanation is that we have stratified by sex and adjusted for comorbidities. In our study the most deprived patients have a higher risk of death, but not of ESKD requiring RRTs, showing socioeconomic inequalities in the worst possible outcome, that probably occurred before the progression of the disease in most deprived patients. Further studies are needed to confirm this association that can lead both individual and Public Health decisions.