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Table 3.

Adjusted HRs and 95% CIs for incident breast cancer by region of residence at baseline (Southern vs Northern residence) and solar irradiance (low vs high solar exposure) stratified by breast cancer tumor characteristics: the WHIOS (n = 71,662)

CasesNorthern (>40°) vs Southern (≤37°)Langleys (gm-cal) per cm2 (300-325 vs 475-500)Watts (J/s) per m2 (0.4-0.5 vs 1.5-1.9)
ER status     
    ER+ 1,932 1.02 (0.92, 1.13) 0.97 (0.86, 1.11) 0.86 (0.73, 1.01) 
    ER− 346 0.97 (0.76, 1.25) 0.90 (0.65, 1.25) 1.00 (0.69, 1.46) 
PR status     
    PR+ 1,607 1.07 (0.95, 1.20) 1.08 (0.94, 1.25) 0.90 (0.75, 1.08) 
    PR− 634 0.90 (0.75, 1.08) 0.71 (0.56, 0.90) 0.79 (0.61, 1.04) 
ER/PR status     
    ER+/PR+ 1,572 1.07 (0.96, 1.21) 1.09 (0.94, 1.26) 0.90 (0.75, 1.08) 
    ER+/PR− 322 0.83 (0.64, 1.07) 0.59 (0.42, 0.82) 0.64 (0.45, 0.93) 
    ER−/PR+ 35 0.77 (0.36, 1.67) 0.83 (0.30, 2.33) 0.79 (0.25, 2.48) 
    ER−/PR− 305 1.00 (0.77, 1.30) 0.90 (0.63, 1.27) 1.01 (0.68, 1.52) 
Tumor size (cm)     
    <0.5 186 1.04 (0.73, 1.47) 0.96 (0.60, 1.53) 1.49 (0.84, 2.66) 
    0.5-1 475 1.20 (0.97, 1.49) 1.02 (0.79, 1.33) 0.96 (0.69, 1.33) 
    >1 to 2 982 0.90 (0.78, 1.05) 0.88 (0.73, 1.05) 0.75 (0.60, 0.93) 
    >2 to 5 497 1.09 (0.89, 1.35) 1.03 (0.79, 1.35) 0.98 (0.70, 1.35) 
    >5 86 0.49 (0.30, 0.79) 0.45 (0.26, 0.80) 0.49 (0.23, 1.03) 
Lymph node involvement     
    No 1,817 1.00 (0.89, 1.11) 0.99 (0.87, 1.13) 0.84 (0.71, 0.99) 
    Yes 610 0.92 (0.79, 1.06) 0.82 (0.65, 1.04) 0.80 (0.60, 1.06) 
Tumor grade     
    Well-differentiated 631 0.93 (0.77, 1.12) 0.74 (0.59, 0.92) 0.53 (0.40, 0.70) 
    Moderately differentiated 972 0.92 (0.79, 1.06) 0.97 (0.81, 1.16) 0.78 (0.62, 0.98) 
    Poorly differentiated 567 1.15 (0.95, 1.41) 1.23 (0.95, 1.60) 1.30 (0.94, 1.80) 
    Anaplastic 64 1.50 (0.84, 2.68) 1.06 (0.51, 2.22) 1.46 (0.67, 3.17) 
CasesNorthern (>40°) vs Southern (≤37°)Langleys (gm-cal) per cm2 (300-325 vs 475-500)Watts (J/s) per m2 (0.4-0.5 vs 1.5-1.9)
ER status     
    ER+ 1,932 1.02 (0.92, 1.13) 0.97 (0.86, 1.11) 0.86 (0.73, 1.01) 
    ER− 346 0.97 (0.76, 1.25) 0.90 (0.65, 1.25) 1.00 (0.69, 1.46) 
PR status     
    PR+ 1,607 1.07 (0.95, 1.20) 1.08 (0.94, 1.25) 0.90 (0.75, 1.08) 
    PR− 634 0.90 (0.75, 1.08) 0.71 (0.56, 0.90) 0.79 (0.61, 1.04) 
ER/PR status     
    ER+/PR+ 1,572 1.07 (0.96, 1.21) 1.09 (0.94, 1.26) 0.90 (0.75, 1.08) 
    ER+/PR− 322 0.83 (0.64, 1.07) 0.59 (0.42, 0.82) 0.64 (0.45, 0.93) 
    ER−/PR+ 35 0.77 (0.36, 1.67) 0.83 (0.30, 2.33) 0.79 (0.25, 2.48) 
    ER−/PR− 305 1.00 (0.77, 1.30) 0.90 (0.63, 1.27) 1.01 (0.68, 1.52) 
Tumor size (cm)     
    <0.5 186 1.04 (0.73, 1.47) 0.96 (0.60, 1.53) 1.49 (0.84, 2.66) 
    0.5-1 475 1.20 (0.97, 1.49) 1.02 (0.79, 1.33) 0.96 (0.69, 1.33) 
    >1 to 2 982 0.90 (0.78, 1.05) 0.88 (0.73, 1.05) 0.75 (0.60, 0.93) 
    >2 to 5 497 1.09 (0.89, 1.35) 1.03 (0.79, 1.35) 0.98 (0.70, 1.35) 
    >5 86 0.49 (0.30, 0.79) 0.45 (0.26, 0.80) 0.49 (0.23, 1.03) 
Lymph node involvement     
    No 1,817 1.00 (0.89, 1.11) 0.99 (0.87, 1.13) 0.84 (0.71, 0.99) 
    Yes 610 0.92 (0.79, 1.06) 0.82 (0.65, 1.04) 0.80 (0.60, 1.06) 
Tumor grade     
    Well-differentiated 631 0.93 (0.77, 1.12) 0.74 (0.59, 0.92) 0.53 (0.40, 0.70) 
    Moderately differentiated 972 0.92 (0.79, 1.06) 0.97 (0.81, 1.16) 0.78 (0.62, 0.98) 
    Poorly differentiated 567 1.15 (0.95, 1.41) 1.23 (0.95, 1.60) 1.30 (0.94, 1.80) 
    Anaplastic 64 1.50 (0.84, 2.68) 1.06 (0.51, 2.22) 1.46 (0.67, 3.17) 

NOTE: Adjusted for age, race/ethnicity, education, weight, family history of breast cancer, age at menarche, age at menopause, parity, age at first birth, hormone therapy duration of use, alcohol intake, and physical activity.

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