# Difference in Age- and Sex-adjusted Prevalence of Diseases between Employees and Nonemployees with Health Insurance in Japan

## TL;DR

This study compares disease prevalence between employees and nonemployees in Japan, showing significant differences after adjusting for age and sex.

## Contribution

The study provides new insights into how insurance type affects disease prevalence after age- and sex-adjustment.

## Key findings

- Kokuho insurance holders had higher crude prevalence in several diseases like malignancies and cardiovascular diseases.
- After adjustment, Kokuho showed higher rates of mental and neurological disorders compared to Kempo.
- Gastrointestinal disease prevalence was notably lower in the Kokuho group after adjustment.

## Abstract

Administrative claims data are used in clinical studies. However, individuals insured by different insurance systems have different backgrounds, ages, and disease prevalences. This study aimed to examine the crude and adjusted prevalence of diseases between employee and nonemployee health insurance in Japan.

We conducted a cross-sectional study using the DeSC database, an administrative claims database covering multiple insurers. We calculated the prevalence of 10 disease categories and 6 specific cancers with and without adjustments for age and sex and compared them between the employee (Kempo) and nonemployee (Kokuho) insurance systems.

We identified 740,217 and 3,312,042 individuals covered by Kempo and Kokuho, respectively. The Kokuho group showed a higher crude prevalence of malignancies, endocrinological diseases, mental disorders, neurological diseases, cardiovascular diseases, and kidney or genitourinary diseases. The adjusted prevalence differed in mental disorders (7.2% vs. 10.6%), neurological diseases (10.5% vs. 14.0%), and gastrointestinal diseases (50.1% vs. 34.1%) between the Kempo and Kokuho groups.

While using administrative claims data, researchers should consider differences in patient backgrounds and disease prevalence among insurance providers.