Table 2.
Plasma Vitamin C Concentrations in the Sub-cohort of the Linxian General Population Nutrition Intervention Trial by Selected Characteristics, China, 1999-2016a
| Characteristic | No. of subjects | Percentile of vitamin C concentrations (μmol/L) |
P valueb | |||||
|---|---|---|---|---|---|---|---|---|
| IQR | 5th | 25th | 50th | 75th | 95th | |||
| Sub-cohort | 948 | 41.6 | 5.0 | 13.5 | 32.7 | 55.2 | 72.6 | |
| Season of blood drawc | ||||||||
| Winter, 1999 | 457 | 27.5 | 11.4 | 34.8 | 51.5 | 62.3 | 76.4 | |
| Spring, 2000 | 487 | 23.0 | 3.7 | 9.1 | 16.8 | 32.2 | 64.9 | <0.0001 |
| Sex | ||||||||
| Male | 473 | 39.2 | 3.6 | 10.7 | 26.7 | 50.0 | 70.2 | |
| Female | 475 | 41.0 | 6.0 | 16.4 | 37.3 | 57.4 | 75.3 | <0.0001 |
| Age at blood draw | ||||||||
| <65 year | 506 | 39.2 | 5.3 | 15.4 | 34.4 | 54.6 | 72.3 | |
| ≥65 year | 442 | 43.0 | 4.0 | 11.4 | 26.3 | 54.4 | 71.4 | 0.03 |
| Smokingd | ||||||||
| No | 637 | 41.0 | 5.4 | 15.4 | 35.3 | 56.5 | 73.5 | |
| Yes | 307 | 37.7 | 3.6 | 5.5 | 25.9 | 48.0 | 71.4 | 0.0003 |
a
Plasma Vitamin C concentration were weighted, accounting for age and sex, to the entire original General Population Nutrition Intervention Trial cohort.
b
Wilcoxon’s-Mann-Whitney test/K-sample test for the equality of medians.
c
Blood samples were collected in winter (November and December) of 1999 and in spring (March and April) of 2000.
d
Smoker was defined as ever smoking cigarettes for 6 or more months.