Characteristics of the case and control groups
| Cases (n=40) | Controls (n=98) | |
| Birth year (%) | ||
| 1935 or before | 4 (10.0) | 24 (24.5) |
| 1936–1945 | 17 (42.5) | 33 (33.7) |
| 1946–1955 | 13 (32.5) | 32 (32.7) |
| 1956 or after | 6 (15.0) | 9 (9.2) |
| Age* | ||
| Median | 50.8 | 52.9 |
| <45 years (%) | 11 (27.5) | 19 (19.4) |
| 45–54 years (%) | 18 (45.0) | 37 (37.8) |
| 55–64 years (%) | 11 (27.5) | 32 (32.7) |
| ≥65 years (%) | 0 (0) | 10 (10.2) |
| Number of females (%) | 28 (70.0) | 65 (66.3) |
| Educational level | ||
| Illiterate (%) | 2 (5.0) | 7 (7.1) |
| Elementary (%) | 19 (47.5) | 48 (49.0) |
| Junior high (%) | 9 (22.5) | 20 (20.4) |
| Senior high (%) | 6 (15.0) | 17 (17.3) |
| College (%) | 3 (7.5) | 5 (5.1) |
| Lifestyle factors | ||
| Smoking habit (>3 days/week for >6 months) (%) | 8 (20) | 17 (17.3) |
| Habitual alcohol consumption (> once per week for >6 months) (%) | 7 (17.5) | 12 (12.2) |
| Habitual tea consumption (>3 days/week for >6 months) (%) | 14 (35.0) | 37 (37.8) |
| Habitual consumption of fermented food (> once per week) (%) | 7 (17.5) | 8 (8.2) |
| Habitual consumption of smoked food (> once per week) (%) | 2 (5.0) | 2 (2.0) |
| History of drinking deep well water (%) | 8 (21.1) | 19 (20.9) |
| Type of herbs sold in store | ||
| Traditional herbal medicine (%) | 11 (27.5) | 28 (28.6) |
| Patent Chinese medicine (%) | 2 (5.0) | 5 (5.1) |
| Both (%) | 20 (50.0) | 32 (32.7) |
| Number of years spent manufacturing or selling Chinese herbal medicine (SD) | 19.1 (15.0) | 21.0 (19.8) |
| Daily work hours (SD) | 7.1 (4.5) | 6.0 (5.0) |
| Procedures in which they participated | ||
| Cutting (%) | 15 (37.5) | 40 (40.8) |
| Refining (%) | 10 (25.0) | 37 (37.8) |
| Grinding (%) | 15 (37.5) | 39 (39.8) |
| Selling (%) | 25 (62.5) | 44 (44.9) |
| solar drying (%) | 13 (32.5) | 35 (35.7) |
| Prescribing patent Chinese medicine (%) | 8 (20.0) | 22 (22.4) |
↵* Age at diagnosis of chronic renal failure of cases and the age of the matched controls at the time of the survey.