Table 1.
Baseline characteristics of the study population by β-carotene intake*
| Intake of β-carotene† |
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|---|---|---|---|---|
| Parameter‡ | 1 (n = 19 570) | 2 (n = 19 531) | 3 (n = 19 386) | 4 (n = 1423) |
| No. of person-years | 130 469 | 131 156 | 129 660 | 9379 |
| Age, y, mean (±SD) | 53.6 (±6.5) | 54.3 (±6.6) | 55.1 (±6.7) | 54.2 (±6.3) |
| Mean daily dietary intake of β-carotene, μg; mean (±SD) | 2285.6 (±568.3) | 3731.8 (±389.6) | 5929.9 (±1428.1) | 4207.2 (±1829.0) |
| Smoking, ever, § % | 31.6 | 29.6 | 29.9 | 34.8 |
| Current smoking, || % | 34.3 | 26.5 | 23.5 | 26.3 |
| No. of pack-years, || mean (±SD) | 10.2 (±10.7) | 9.0 (±9.4) | 9.1 (±9.3) | 9.4 (±9.7) |
| No. of cigarettes per day, || mean (±SD) | 10.7 (±7.8) | 10.0 (±7.0) | 10.3 (±7.4) | 10.4 (±7.8) |
| No. of years of smoking, || mean (±SD) | 17.6 (±10.5) | 16.7 (±10.1) | 16.5 (±10.1) | 16.9 (±9.7) |
| No. of years since quitting tobacco,¶ mean (±SD) | 17.2 (±8.6) | 17.6 (±8.7) | 17.4 (±8.8) | 17.4 (±8.3) |
| Leisure physical activity, min/day; mean (±SD) | 39.8 (±82.5) | 45.8 (±87.7) | 47.5 (±91.2) | 56.8 (±98.1) |
| Alcohol intake, g/day; mean (±SD) | 12.2 (±15.2) | 10.9 (±13.5) | 10.0 (±13.0) | 10.3 (±13.7) |
| Energy, kcal/day; mean (±SD) | 1880.2 (±508.1) | 2047.1 (±510.3) | 2177.1 (±542.9) | 2035.3 (±546.2) |
| Body mass index, kg/m2, mean (±SD) | 22.9 (±3.5) | 23.2 (±4.0) | 23.7 (±3.9) | 22.4 (±3.1) |
| No. of years of schooling <12, % | 11.6 | 10.7 | 11.3 | 7.5 |
| Family history of cancer, # % | 45.0 | 46.0 | 45.7 | 46.5 |
*
The study population was composed of 59 210 cancer-free women and 700 women with tobacco-related cancers (digestive, gynecologic, thyroid, lung, head and-neck, and urinary tract cancers).
†
β-carotene intake: 1 – first tertile of dietary β-carotene intake, 2 – second tertile of dietary β-carotene intake, 3 – third tertile of dietary β-carotene intake, 4 – intake of β-carotene supplements at least three times a week.
‡
SD – standard deviation.
§
Occasional smokers were considered as nonsmokers.
||
In ever smokers.
¶
In past smokers.
#
In first-degree relatives (i.e., parents, children, brothers, and sisters).