Table 2.

ORs and 95% CIs for an association between vitamin D–related exposure variables at ages 10 to 19 (sun exposure and dietary vitamin D) and breast cancer in cases and controls

Cases (%)Controls (%)OR* (95% CI)OR (95% CI)
Days outside per week
    <368 (7)47 (4)1.69 (1.15-2.49)1.49 (1.00-2.22)
    3-464 (7)62 (5)1.26 (0.87-1.81)1.23 (0.85-1.80)
    5-6130 (14)185 (13)0.86 (0.67-1.10)0.82 (0.63-1.06)
    7700 (73)835 (74)1.001.00
    P for trend0.13
Outdoor activity episodes§
    <828266 (29)263 (24)1.001.00
    828-1,295238 (26)265 (24)0.90 (0.71-1.16)0.87 (0.67-1.12)
    1,296-2,039218 (24)287 (26)0.76 (0.59-0.97)0.74 (0.57-0.96)
    2,040+181 (20)285 (26)0.65 (0.50-0.83)0.65 (0.50-0.85)
    P for trend<0.0006
Outdoor job
    Never809 (83)846 (75)1.001.00
    1 y67 (7)114 (10)0.65 (0.47-0.89)0.69 (0.50-0.96)
    ≥1 y96 (10)175 (15)0.58 (0.44-0.75)0.61 (0.46-0.80)
    P for trend<0.0001
Limbs covered
    No730 (76)937 (83)1.001.00
    Partial160 (17)149 (13)1.36 (1.06-1.73)1.36 (1.06-1.75)
    Yes73 (8)49 (4)1.85 (1.27-2.70)1.68 (1.14-2.50)
    P for trend0.0008
Skin burned/darkened
    No82 (9)59 (5)1.65 (1.16-2.33)1.55 (1.08-2.24)
    Yes881 (91)1,073 (95)1.001.00
Sunscreen use
    No895 (94)1,051 (94)1.001.00
    Yes58 (6)73 (6)1.01 (0.70-1.45)1.04 (0.72-1.51)
Sun trip in winter
    No779 (86)907 (80)1.001.00
    Yes127 (14)180 (16)0.91 (0.70-1.73)1.00 (0.77-1.30)
Sunlamp Use
    No912 (94)1,036 (91)1.001.00
    Yes60 (6)99 (9)0.72 (0.52-1.01)0.81 (0.57-1.14)
Cod liver oil use
    No618 (64)682 (61)1.001.00
    Yes342 (36)444 (39)0.77 (0.64-0.93)0.76 (0.62-0.92)
Milk (glasses/wk)
    None119 (12)85 (7)1.001.00
    <5129 (13)110 (10)0.89 (0.61-1.30)0.95 (0.64-1.41)
    5-9224 (23)266 (23)0.62 (0.45-0.87)0.67 (0.48-0.95)
    ≥10500 (51)674 (59)0.54 (0.40-0.74)0.62 (0.45-0.86)
    P for trend0.0004
Intake of salmon or tuna per week
    None273 (28)286 (25)1.001.00
    <1269 (28)267 (24)1.05 (0.83-1.33)1.10 (0.86-1.41)
    1285 (29)382 (34)0.77 (0.61-0.97)0.82 (0.65-1.04)
    >1145 (15)200 (18)0.76 (0.58-0.99)0.86 (0.64-1.14)
    P for trend0.06
Supplement use
    Vitamin D or multivitamins145 (15)252 (22)0.60 (0.48-0.76)0.62 (0.49-0.79)
    Other vitamin supplements69 (7)129 (11)0.54 (0.40-0.73)0.53 (0.39-0.73)
    None758 (78)754 (66)1.001.00
  • * ORs with 95% CIs adjusted for reference age.

  • ORs with 95% CIs adjusted for reference age, ethnicity, family history in first-degree relatives, ever breast-fed, education, age menarche, and age at first birth.

  • Number of days outside for at least half an hour during the summer (June, July, and August).

  • § Number of outdoor activity episodes derived from reported outdoor activities done for at least 30 min between 9 a.m. and 5 p.m. at least once per month during June, July, and August along with frequency (days per week or month) and duration (number of years).