Table 3.
The relative risk for incident non-melanoma skin cancer according to frequency of citrus juice consumption among Women’s Health Initiative participants (n = 49,007) by subgroups of potential effect modifiers.
| Citrus Juice Serving Category | p-Trend | |||||
|---|---|---|---|---|---|---|
| <2/wk | 2–4/wk | 5–6/wk | 1–1.4/d | ≥1.5/d | ||
| Regional solar radiation | ||||||
| 300–350 | ||||||
| Number of cases (%) | 1640 (15.1) | 390 (15.9) | 824 (17.1) | 267 (16.2) | 1321 (18.1) | |
| Adjusted RR (95% CI) | (ref) | 1.04 (0.94, 1.15) | 1.09 (1.00, 1.17) | 1.03 (0.92, 1.16) | 1.12 (1.04, 1.19) | 0.002 |
| 375–500 | ||||||
| Number of cases (%) | 1932 (18.4) | 378 (19.2) | 707 (20.3) | 241 (18.0) | 942 (20.3) | |
| Adjusted RR (95% CI) | (ref) | 1.00 (0.91, 1.11) | 1.05 (0.97, 1.14) | 0.93 (0.83, 1.06) | 1.04 (0.97, 1.12) | 0.353 |
| Skin reaction to sun | ||||||
| No burn, with or without tanning | ||||||
| Number of cases (%) | 1094 (14.0) | 218 (13.7) | 488 (15.3) | 163 (15.1) | 683 (15.9) | |
| Adjusted RR (95% CI) | (ref) | 0.98 (0.85, 1.12) | 1.06 (0.96, 1.17) | 1.06 (0.91, 1.24) | 1.09 (1.00, 1.20) | 0.034 |
| Burn, with or without tanning | ||||||
| Number of cases (%) | 2478 (18.3) | 550 (19.5) | 1043 (20.4) | 345 (18.1) | 1580 (20.7) | |
| Adjusted RR (95% CI) | (ref) | 1.04 (0.95, 1.13) | 1.07 (1.01, 1.15) | 0.95 (0.86, 1.05) | 1.08 (1.02, 1.14) | 0.028 |
| Time Outdoors in Summer Currently | ||||||
| <30 min/day | ||||||
| Number of cases (%) | 1004 (15.1) | 186 (14.8) | 402 (16.7) | 149 (17.9) | 597 (17.4) | |
| Adjusted RR (95% CI) | (ref) | 0.95 (0.82, 1.10) | 1.07 (0.96, 1.19) | 1.15 (0.98, 1.34) | 1.10 (1.01, 1.21) | 0.015 |
| >30 min/day | ||||||
| Number of cases (%) | 2568 (17.5) | 582 (18.5) | 1129 (19.1) | 359 (16.7) | 1666 (19.6) | |
| Adjusted RR (95% CI) | (ref) | 1.04 (0.96, 1.13) | 1.07 (1.00, 1.14) | 0.93 (0.84, 1.03) | 1.07 (1.01, 1.13) | 0.040 |
| Sunscreen Use | ||||||
| No sunscreen use | ||||||
| Number of cases (%) | 1471 (13.6) | 285 (13.9) | 589 (14.8) | 199 (14.0) | 865 (15.6) | |
| Adjusted RR (95% CI) | (ref) | 1.01 (0.90, 1.14) | 1.06 (0.97, 1.16) | 0.99 (0.86, 1.14) | 1.10 (1.02, 1.19) | 0.020 |
| Sunscreen Use (any or unknown SPF) | ||||||
| Number of cases (%) | 2101 (19.9) | 483 (20.4) | 942 (21.7) | 309 (19.8) | 1398 (21.9) | |
| Adjusted RR (95% CI) | (ref) | 1.03 (0.94, 1.12) | 1.07 (1.00, 1.15) | 0.98 (0.88, 1.09) | 1.07 (1.01, 1.14) | 0.042 |
Adjusted for age (continuous), BMI (<25.0, 25.0–29.9, 30.0–34.9, ≥35.0 kg/m2), education (less than high school graduate, high school graduate, some college, and college graduate), physical activity (inactive, low activity, moderate activity, and high activity), alcohol consumption (continuous), regional solar radiation (300–325, 350, 375–380, 400–430, and 475–500 Langleys), skin reaction to sun (no burns, with or without tanning; burns, and with or without tanning), average daily time outdoors currently (<30 min, 30 min–2 h, and 2+ h), and sunscreen SPF use (none, something but does not know, SPF 2–14, SPF 15–24, and SPF 25+). The stratifying variable was removed in its stratified analysis.