Table 1. Population Characteristics by Quartiles of Dietary Niacin Intake.
| Variable | Participants, No. (%) | P value | |||
|---|---|---|---|---|---|
| Q1 (<12.4 mg/d) (n = 3061) | Q2 (12.4 to <14.3 mg/d) (n = 3060) | Q3 (14.3 to <16.7 mg/d) (n = 3061) | Q4 (≥16.7 mg/d) (n = 3061) | ||
| Men | 1340 (43.8) | 1317 (43.0) | 1399 (45.7) | 1672 (54.6) | <.001 |
| Age, mean (SD), y | 41.5 (14.6) | 42.0 (14.3) | 40.7 (14.0) | 40.5 (13.7) | <.001 |
| Blood pressure, mean (SD), mm Hg | |||||
| Systolic | 114.5 (11.3) | 113.8 (11.5) | 113.1 (11.5) | 114.2 (11.4) | <.001 |
| Diastolic | 74.3 (7.9) | 74.3 (7.9) | 73.6 (7.8) | 74.4 (7.8) | <.001 |
| BMI, mean (SD) | 22.7 (3.1) | 22.2 (3.0) | 22.2 (3.0) | 22.5 (3.1) | <.001 |
| Waist to hip ratio, mean (SD) | 0.9 (0.1) | 0.8 (0.1) | 0.8 (0.1) | 0.9 (0.1) | <.001 |
| Smoking status | 882 (28.9) | 853 (28.1) | 920 (30.2) | 1053 (34.5) | <.001 |
| Drinking status | 972 (32.1) | 931 (30.9) | 1019 (33.7) | 1242 (40.9) | <.001 |
| Urban residence | 926 (30.3) | 940 (30.7) | 1170 (38.2) | 1379 (45.1) | <.001 |
| Region | |||||
| East and central | 2187 (71.4) | 1505 (49.2) | 1398 (45.7) | 1421 (46.4) | <.001 |
| Northeast and north | 525 (17.2) | 779 (25.5) | 614 (20.1) | 571 (18.7) | |
| Southwest and south | 349 (11.4) | 776 (25.4) | 1049 (34.3) | 1069 (34.9) | |
| Occupation | |||||
| Farmer | 1231 (40.8) | 1328 (44.0) | 1097 (36.0) | 728 (24.0) | <.001 |
| Worker | 333 (11.0) | 304 (10.1) | 382 (12.6) | 441 (14.5) | |
| Unemployed | 819 (27.2) | 721 (23.9) | 719 (23.6) | 790 (26.0) | |
| Other | 631 (20.9) | 668 (22.1) | 845 (27.8) | 1076 (35.5) | |
| Education | |||||
| Illiteracy | 684 (22.8) | 644 (21.6) | 517 (17.2) | 369 (12.2) | <.001 |
| Primary school | 604 (20.2) | 637 (21.4) | 599 (19.9) | 503 (16.6) | |
| Middle school | 1021 (34.1) | 995 (33.4) | 992 (33.0) | 1008 (33.3) | |
| ≥High school | 685 (22.9) | 705 (23.6) | 902 (30.0) | 1143 (37.8) | |
| Self-report diabetes | 35 (1.2) | 35 (1.2) | 37 (1.2) | 47 (1.6) | .47 |
| Dietary intake | |||||
| Energy, mean (SD), Kcal/d | 2276.2 (578.7) | 2162.7 (519.8) | 2120.6 (485.7) | 2207.0 (566.2) | <.001 |
| Fat, mean (SD), g/d | 75.6 (32.6) | 69.5 (28.7) | 72.7 (27.1) | 80.9 (30.4) | <.001 |
| Carbohydrate, mean (SD), g/d | 334.9 (110.4) | 321.8 (101.3) | 301.1 (94.4) | 292.7 (100.7) | <.001 |
| Protein, mean (SD), g/d | 64.1 (18.7) | 62.6 (17.1) | 65.4 (15.8) | 77.0 (24.5) | <.001 |
| Sodium, mean (SD), g/d | 5.5 (3.3) | 5.0 (3.1) | 4.7 (2.6) | 4.9 (3.0) | <.001 |
| Potassium, mean (SD), g/d | 1.6 (0.5) | 1.6 (0.5) | 1.7 (0.5) | 1.9 (1.0) | <.001 |
| Na:K ratio | 3.8 (2.5) | 3.3 (2.1) | 3.0 (1.7) | 2.7 (1.8) | <.001 |
| Vegetables, mean (SD), g/d | 329.0 (138.1) | 361.3 (138.4) | 385.9 (144.4) | 418.9 (185.3) | <.001 |
| Fruit intake | 1201 (39.2) | 1354 (44.2) | 1510 (49.3) | 1543 (50.4) | <.001 |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); Na:K, sodium to potassium.
SI conversion factor: To convert niacin to μmol/d, multiply by 8.123.