Income and professional inequalities in chronic diseases: prevalence and incidence in France.

Objectives: In France, almost nine of 10 deaths are caused by non-communicable diseases, and there is significant social inequality in mortality rates. However, it is not easy to collect robust data on the incidence and prevalence of such diseases according to socio-economic status. Based on data from the link between the primary longitudinal population sample and the national health data system, the aim of our study was to compute the standardised incidence and prevalence of seven major groups of chronic diseases according to socio-economic status.

Study Design: Descriptive retrospective cohort study.

Methods: This was a descriptive retrospective cohort study on a weighted representative sample of the French population, comprising 3.4 million individuals from data collected 2016-2017. Main chronic disease categories include diabetes, cancers, psychiatric disorders, liver and pancreatic diseases, neurological conditions, respiratory and cardiovascular diseases, calculated from the 2016-2017 period by combining health care consumption and diagnoses received during hospitalisations and/or associated with specific full healthcare coverage. Socio-economic status was measured by disposable income from the 2013-2014 tax returns and census-derived socioprofessional groups, and findings were standardised for age and sex.

Results: For all disease categories except cancers, standardised incidence rates showed a gradient favouring the wealthiest, with a risk ratio between the first and tenth standard of living deciles ranging from 1.4 (cardiovascular diseases) to 2.8 (diabetes). Incidence of all disease categories, except cancers, was higher for all groups compared with executives and higher academic professions (risk ratios between workers and executives ranged from 2.0 to 1.3 in psychiatric and cardiovascular diseases, respectively). Conversely, cancer incidence rate followed a flat curve, reduced in the two poorest standard of living deciles, and there were no significant differences between socioprofessional groups. Standardised prevalence rates followed the same patterns, although risk ratios were highest for psychiatric diseases, varying according to sex and disease.

Conclusions: Deep social inequalities in incidence and prevalence of chronic diseases were observed in a large representative sample of the French population. The reverse social inequalities in cancer incidence and prevalence calls for more detailed research into cancer types and selection mechanisms, the data from which would allow the long-term monitoring of such disparities.