TABLE 1.
General characteristics of the study subjectsa.
| Variables | Case (n = 850) | Control (n = 861) | P-value |
| Age (years) mean ± SD | 48.33 ± 9.59 | 48.33 ± 9.53 | 0.991 |
| BMI (kg/m2) mean ± SD | 23.32 ± 3.70 | 22.68 ± 3.36 | <0.001 |
| Household and recreational activities, MET-h/week (mean ± SD) | 36.47 ± 23.73 | 40.50 ± 24.91 | 0.001 |
| Occupation [n (%)] | 0.647 | ||
| Administrator/other white-collar workers | 176 (20.71) | 190 (22.07) | |
| Blue-collar worker | 233 (27.41) | 243 (28.22) | |
| Farmer/other | 441 (51.88) | 428 (49.71) | |
| Education [n (%)] | 0.001 | ||
| Primary school or below | 209 (24.59) | 231 (26.83) | |
| Secondary school | 257 (30.24) | 198 (22.99) | |
| High school | 198 (23.29) | 190 (22.07) | |
| College or above | 186 (21.88) | 242 (28.11) | |
| Income, Yuan/month [n (%)] | 0.192 | ||
| ≤2,000 | 50 (5.88) | 47 (5.46) | |
| 2,001–5,000 | 257 (30.24) | 223 (25.90) | |
| 5,001–8,000 | 307 (36.12) | 325 (37.75) | |
| ≥8,001 | 236 (27.76) | 266 (30.89) | |
| Regular smoker [n (%)] | 12 (1.41) | 10 (1.16) | 0.646 |
| Regular drinker [n (%)] | 76 (8.94) | 45 (5.23) | 0.003 |
| Passive smoker [n (%)] | 319 (37.53) | 327 (37.98) | 0.848 |
| Menopausal status [n (%)] | 0.998 | ||
| Premenopausal | 537 (63.18) | 544 (63.18) | |
| Postmenopausal | 313 (36.82) | 317 (36.82) | |
| First-degree relatives with cancer [n (%)] | 126 (14.82) | 81 (9.41) | 0.001 |
| Energy intake (kcal/day) mean ± SD | 1511.09 ± 405.93 | 1544.99 ± 399.33 | 0.081 |
| Dietary fatty acid intake (mean ± SD)b | |||
| ALA (g/day) | 0.75 ± 0.22 | 0.77 ± 0.22 | 0.007 |
| Long-chain n – 3 PUFAs (mg/day) | 57.04 ± 6.65 | 59.51 ± 6.52 | 0.024 |
| Total n – 3 PUFAs (g/day) | 0.81 ± 0.24 | 0.83 ± 0.23 | 0.005 |
| Erythrocyte PUFAs, % of total fatty acids, mean ± SD | |||
| ALA | 0.41 ± 0.17 | 0.45 ± 0.18 | <0.001 |
| EPA | 0.84 ± 0.42 | 0.94 ± 0.52 | <0.001 |
| DPA | 1.09 ± 0.54 | 1.21 ± 0.66 | <0.001 |
| DHA | 3.20 ± 0.80 | 3.40 ± 0.86 | <0.001 |
| Total n – 3 PUFAs | 5.72 ± 1.52 | 6.35 ± 1.75 | <0.001 |
ALA, α-linolenic acid; DHA, docosahexaenoic acid; DPA, docosapentaenoic acid; EPA, Eicosapentaenoic acid; PUFA polyunsaturated fatty acid; SD standard deviation.
aMann-Whitney U-test was used for the comparison of continuous variables between cases and controls. Chi-square test was used to test the differences of categorical variables.
bDietary intakes were adjusted for total energy using the residual method.