Table 3.

ORs and 95% CIs for an association between vitamin D–related exposure variables at ages 20 to 29 (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
    <3161 (17)128 (11)1.49 (1.15-1.93)1.40 (1.07-1.84)
    3-4106 (11)148 (13)0.85 (0.65-1.12)0.86 (0.65-1.14)
    5-6132 (14)209 (19)0.74 (0.58-0.95)0.72 (0.56-0.93)
    7557 (58)645 (57)1.001.00
    P for trend0.17
Outdoor activity episodes§
    <480251 (28)230 (21)1.001.00
    480-869206 (23)291 (26)0.65 (0.50-0.83)0.65 (0.50-0.85)
    870-1,319227 (25)285 (26)0.72 (0.56-0.92)0.72 (0.55-0.93)
    1,320+207 (23)293 (27)0.64 (0.49-0.82)0.65 (0.50-0.85)
    P for trend0.005
Outdoor job
    Never893 (92)1,043 (92)1.001.00
    1 y33 (3)40 (4)1.04 (0.65-1.67)1.06 (0.65-1.74)
    ≥1 y46 (5)52 (5)1.11 (0.74-1.68)1.22 (0.80-1.86)
    P for trend0.35
Limbs covered
    No696 (72)875 (77)1.001.00
    Partial176 (18)192 (17)1.16 (0.92-1.46)1.13 (0.89-1.42)
    Yes93 (10)67 (6)1.75 (1.26-2.44)1.68 (1.20-2.37)
    P for trend0.004
Skin burned/darkened
    No76 (8)79 (7)1.15 (0.83-1.60)1.06 (0.75-1.49)
    Yes888 (92)1,056 (93)1.001.00
Sunscreen use
    No751 (79)836 (74)1.001.00
    Yes205 (21)290 (26)0.85 (0.68-1.04)0.89 (0.72-1.11)
Sun trip in winter
    No626 (67)731 (66)1.001.00
    Yes313 (33)379 (34)1.02 (0.85-1.23)1.05 (0.86-1.28)
Sunlamp Use
    No869 (89)981 (86)1.001.00
    Yes104 (11)154 (14)0.86 (0.65-1.13)0.88 (0.66-1.18)
Cod liver oil use
    No945 (98)1,101 (98)1.001.00
    Yes15 (2)25 (2)0.70 (0.36-1.33)0.61 (0.31-1.21)
Milk (glasses/wk)
    None163 (17)126 (11)1.001.00
    <5193 (20)187 (16)0.83 (0.61-1.13)0.81 (0.57-1.11)
    5-9251 (26)320 (28)0.62 (0.46-0.82)0.64 (0.48-0.87)
    ≥10365 (38)502 (44)0.57 (0.43-0.74)0.63 (0.47-0.83)
    P for trend0.0006
Intake of salmon or tuna per week
    None158 (16)177 (16)1.001.00
    <1304 (31)324 (29)1.04 (0.80-1.36)1.07 (0.81-1.41)
    1299 (31)390 (34)0.83 (0.64-1.08)0.90 (0.68-1.19)
    >1211 (22)244 (22)0.95 (0.72-1.26)1.04 (0.77-1.40)
P for trend0.77
Supplement use
    Vitamin D or multivitamins271 (28)404 (36)0.65 (0.53-0.79)0.67 (0.54-0.82)
    Other vitamin supplements149 (15)222 (20)0.64 (0.50-0.81)0.69 (0.53-0.88)
    None552 (57)509 (45)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).