Table 3.
Pooled Multivariable HRs for Incident Melanoma According to Frequency of Grapefruit Consumption in Subgroups of Potential Confounders*
| Potential Confounder | Grapefruit Serving Category |
Ptrend | Pinteraction† | |||
|---|---|---|---|---|---|---|
| Never | < Once per Week | Once per Wek | ≥ Twice per Week | |||
| Age group, years | ||||||
| < 65 | ||||||
| No. of person-years | 386,342 | 443,482 | 237,215 | 272,430 | ||
| No. of cases | 180 | 314 | 167 | 219 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.23 (1.01 to 1.50) | 1.28 (1.02 to 1.62) | 1.38 (1.10 to 1.73) | .01 | .82 |
| ≥ 65 | ||||||
| No. of person-years | 128,820 | 203,543 | 117,517 | 213,084 | ||
| No. of cases | 137 | 275 | 186 | 362 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.10 (0.89 to 1.37) | 1.31 (1.03 to 1.66) | 1.33 (1.07 to 1.66) | .002 | |
| Body mass index, kg/m2 | ||||||
| < 30 | ||||||
| No. of person-years | 423,239 | 529,285 | 293,553 | 402,710 | ||
| No. of cases | 276 | 487 | 300 | 490 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.10 (0.94 to 1.29) | 1.23 (1.03 to 1.47) | 1.28 (1.08 to 1.52) | .001 | .39 |
| ≥ 30 | ||||||
| No. of person-years | 87,025 | 114,189 | 59,136 | 80,721 | ||
| No. of cases | 41 | 100 | 53 | 89 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.64 (1.11 to 2.43) | 1.71 (1.08 to 2.69) | 1.88 (1.22 to 2.88) | .02 | |
| Physical activity | ||||||
| < Median | ||||||
| No. of person-years | 283,031 | 317,106 | 156,235 | 195,401 | ||
| No. of cases | 155 | 259 | 123 | 213 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.20 (0.74 to 1.94) | 1.16 (0.68 to 1.98) | 1.46 (1.03 to 2.05) | .008 | .90 |
| > Median | ||||||
| No. of person-years | 206,457 | 313,570 | 189,110 | 281,741 | ||
| No. of cases | 157 | 329 | 228 | 363 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.17 (0.83 to 1.65) | 1.39 (0.86 to 2.24) | 1.33 (1.07 to 1.64) | .003 | |
| Smoking status | ||||||
| Never | ||||||
| No. of person-years | 205,283 | 293,329 | 166,494 | 221,425 | ||
| No. of cases | 132 | 279 | 166 | 267 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.22 (0.91 to 1.62) | 1.31 (1.02 to 1.68) | 1.39 (1.07 to 1.82) | .01 | .72 |
| Ever | ||||||
| No. of person-years | 269,419 | 323,488 | 172,901 | 243,694 | ||
| No. of cases | 172 | 289 | 178 | 304 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.11 (0.91 to 1.36) | 1.29 (1.03 to 1.62) | 1.38 (1.11 to 1.71) | .001 | |
| Alcohol intake | ||||||
| < Median | ||||||
| No. of person-years | 275,932 | 321,995 | 166,834 | 228,432 | ||
| No. of cases | 155 | 268 | 136 | 239 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.22 (0.99 to 1.50) | 1.20 (0.93 to 1.54) | 1.37 (1.09 to 1.73) | .02 | .64 |
| > Median | ||||||
| No. of person-years | 239,231 | 325,029 | 187,898 | 257,081 | ||
| No. of cases | 162 | 321 | 217 | 342 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.14 (0.94 to 1.40) | 1.38 (1.11 to 1.73) | 1.37 (1.11 to 1.70) | .001 | |
| Coffee intake, cups per day | ||||||
| Low (< 1.0) | ||||||
| No. of person-years | 227,043 | 282,630 | 157,097 | 225,217 | ||
| No. of cases | 144 | 257 | 173 | 285 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.13 (0.91 to 1.40) | 1.40 (1.10 to 1.78) | 1.37 (1.09 to 1.72) | .002 | .64 |
| High (≥ 1.0) | ||||||
| No. of person-years | 288,120 | 364,394 | 197,635 | 260,298 | ||
| No. of cases | 173 | 332 | 180 | 296 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.20 (0.99 to 1.46) | 1.23 (0.98 to 1.54) | 1.38 (1.12 to 1.71) | .008 | |
| Vitamin C from supplements | ||||||
| < Median | ||||||
| No. of person-years | 283,462 | 324,903 | 169,728 | 214,162 | ||
| No. of cases | 152 | 253 | 135 | 223 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.16 (0.94 to 1.44) | 1.21 (0.94 to 1.56) | 1.40 (1.11 to 1.77) | .01 | .97 |
| > Median | ||||||
| No. of person-years | 231,702 | 322,120 | 185,005 | 271,353 | ||
| No. of cases | 165 | 336 | 218 | 358 | ||
| Multivariable-adjusted HR (95% CI) | 1.00 | 1.19 (0.97 to 1.44) | 1.36 (1.10 to 1.70) | 1.36 (1.11 to 1.68) | .002 | |
Abbreviation: HR, hazard ratio.
Multivariable analyses were adjusted for age, family history of melanoma, natural hair color, No. of arm moles, sunburn susceptibility as child or adolescent, No. of lifetime blistering sunburns, cumulative ultraviolet flux since baseline, average time spent in direct sunlight since high school, body mass index, physical activity, smoking status, and intake of total energy, alcohol, coffee, vitamin C from supplements, and other individual citrus products (grapefruit juice, oranges, and orange juice). Analyses for women were also adjusted for menopausal status and postmenopausal hormone use. For each stratified analysis, stratifying variable was omitted from model, except for age. Results among women and men were pooled using random-effects model.
For pooled analysis, P values for interactions were calculated using Q statistic comparing subgroup-specific pooled multivariable-adjusted HRs for grapefruit consumption as median trend variable.