Table 1. The distribution of general characteristics for cases and controls.
| Characteristics | Cases | Controls | χ2 | P |
| Age (a) | 1.599 | 0.660 | ||
| 45- | 49 (13.61) | 51 (14.17) | ||
| 55- | 71 (19.72) | 63 (17.50) | ||
| 65- | 112 (31.11) | 126 (35.00) | ||
| 75-85 | 128 (35.56) | 120 (33.33) | ||
| Gender | <0.001 | 1.000 | ||
| M | 185 (51.39) | 185 (51.39) | ||
| F | 175 (48.61) | 175 (48.61) | ||
| Occupation | 4.133 | 0.247 | ||
| Worker | 144 (40.00) | 149 (41.39) | ||
| Farmer | 57 (15.83) | 70 (19.44) | ||
| Intellectual | 105 (29.17) | 83 (23.06) | ||
| Other | 54 (15.00) | 58 (16.11) | ||
| Education | 8.663 | 0.034 | ||
| Illiteracy | 55 (15.28) | 38 (10.56) | ||
| Primary school | 108 (30.00) | 101 (28.05) | ||
| Junior high school | 131 (36.39) | 126 (35.00) | ||
| ≥High school | 66 (18.33) | 95 (26.39) | ||
| Long-term residence | 2.920 | 0.232 | ||
| Urban | 275 (76.39) | 282 (78.33) | ||
| Rural | 41 (11.39) | 28 (7.78) | ||
| Other | 44 (12.22) | 50 (13.89) | ||
| Family economic income(¥/month) | 15.452 | 0.001 | ||
| ≤1 000 | 45 (12.50) | 21 (5.83) | ||
| 1 001-2 000 | 128 (35.55) | 107 (29.72) | ||
| 2 001-3 000 | 119 (33.06) | 149 (41.39) | ||
| ≥3 001 | 68 (18.89) | 83 (23.06) | ||
| Smoking | 6.298 | 0.043 | ||
| Never | 181 (50.28) | 217 (60.28) | ||
| Past | 59 (16.39) | 54 (15.00) | ||
| Current | 120 (33.33) | 89 (24.72) | ||
| Alcohol consumption | 5.217 | 0.074 | ||
| Never | 239 (66.39) | 264 (73.33) | ||
| Past | 17 (4.72) | 9 (2.50) | ||
| Current | 104 (28.89) | 87 (24.17) | ||
| Physical activity | 10.407 | 0.005 | ||
| Never | 207 (57.50) | 164 (45.55) | ||
| Occasionally | 88 (24.44) | 109 (30.28) | ||
| Often | 65 (18.06) | 87 (24.17) | ||
| BMI | 11.430 | 0.01 | ||
| <18.5 | 32 (8.89) | 22 (6.11) | ||
| 18.5- | 169 (46.94) | 208 (57.78) | ||
| 24.0- | 114 (31.67) | 104 (28.89) | ||
| ≥28 | 45 (12.50) | 26 (7.22) | ||
| Hypertension | 7.881 | 0.005 | ||
| Yes | 131 (26.67) | 96 (36.39) | ||
| No | 229 (73.33) | 264 (63.61) | ||
n (%)