Baseline characteristics according to individual income.

<p>DM: diabetes mellitus; CGN: chronic glomerulonephritis; CVD: cardiovascular disease; RRF: residual renal function. *Proportion of individual income used for medical expenses was calculated as the percentage of yearly household income per person used each year for yearly self-paid medical expenses. **Frequent visitors were those who visited a doctor at least once every 3 months.</p>