#2116 Socioeconomic position and incidence of chronic kidney disease in Central Italy
Authors: Cesaroni Giulia , Marino Claudia , Davoli Marina , Agabiti Nera 
Published: May 2024

Abstract

Background and Aims
Socioeconomic position is strongly related to most chronic conditions, with higher prevalence, higher incidence, and more adverse outcomes in disadvantaged groups of the population compared to well-off counterparts. Similar to other pathologies, several studies reported inequalities in the prevalence of chronic kidney disease (CKD). Few studies investigated socioeconomic differences in disease incidence, and some analyzed socioeconomic inequalities in long-term outcomes, such as mortality or end-stage renal disease, with conflicting results. We aimed to investigate the association between educational level and CKD in the Lazio Region Longitudinal Study, i.e., the 2011 census cohort of all residents followed through administrative databases from 1 Jan 2012 to 31 Dec 2022.

Method
The Lazio region is one of the twenty Italian regions. With its 5.5 million inhabitants, it is located in central Italy and includes Rome, the Italian capital city. We considered the population enrolled in the Lazio Region Longitudinal Study aged 35-90 years. We used a validated algorithm to identify prevalent cases of CKD at baseline (1 Jan 2012) and incident CKD cases during the follow-up (1 Jan 2012 to 31 Dec 2022). We used the education available for each individual from the census questionnaire to indicate socioeconomic position. We used Cox proportional hazard models to investigate the association between educational level and incidence of CKD. We used age as the time scale to punctually adjust for age, and we adjusted the multivariable models for place of residence, citizenship, marital status, and occupational status.

Results
We selected 3 752 190 25-90-year-olds included in the Lazio Longitudinal Study. We excluded 66 376 prevalent cases, obtaining a study population of 3 685 814 CKD-free individuals. The prevalent cases were more likely males than females, increased with age, were more Italians than foreigners, were diabetics, and residents in Rome compared to the general population. The study population comprised 1 754 781 men with a mean age of 52 years and 1 997 409 women with a mean age of 54 years. During the 11 years of follow-up, we identified 88 784 new CKD cases among men and 70 217 among women, with crude incidence rates of 540 and 364 per 100, 000 person-years, respectively. The age-adjusted models showed a strong association between educational level and CKD incidence in both men and women (Table 1). In men, compared to those with a university degree, those with upper secondary education had a 30% higher risk of suffering from CKD, those with lower secondary education had a 54% higher risk, while the primary educated men had a 70% higher risk. Among women, the excess risk of low-educated compared to those with a university degree was even higher than in men, with HR = 1.33 (95% CI 1.28-1.38), HR = 1.76 (95% CI 1.69-1.82), and HR = 2.24 (95% CI 2.16-2.32) in upper secondary, lower secondary and primary school educated, respectively. The socioeconomic gap was slightly reduced when we adjusted for possible confounders.

Conclusion
We found strong socioeconomic inequalities in CKD incidence. Further analyses will investigate the clinical risk factors that mediate the association between educational level and CKD incidence.