Table 1. Descriptive Characteristics of Participants in the Women’s Circle of Health Follow-up Study, by Cigarette Smoking.
| Characteristic | Participants, No. (%) | P valuea | |||
|---|---|---|---|---|---|
| Never smokers (n = 1141) | Former smokers (n = 468) | Current smokers (n = 317) | Total (N = 1926) | ||
| Age at breast cancer diagnosis, mean (SD), y | 53.0 (11.2) | 58.3 (9.4) | 53.9 (9.6) | 54.4 (10.8) | .001 |
| Age at breast cancer diagnosis, y | |||||
| <40 | 149 (13.1) | 18 (3.8) | 26 (8.2) | 193 (10.0) | .001 |
| 40 to ≤60 | 669 (58.6) | 243 (51.9) | 214 (67.5) | 1126 (58.5) | |
| >60 | 323 (28.3) | 207 (44.2) | 77 (24.3) | 607 (31.5) | |
| Menopausal status | |||||
| Premenopausal | 526 (46.1) | 112 (23.9) | 109 (34.4) | 747 (38.8) | .001 |
| Postmenopausal | 615 (53.9) | 356 (76.1) | 208 (65.6) | 1179 (61.2) | |
| Smoking | |||||
| Never smokers | 1141 (100) | NA | NA | 1141 (59.2) | NA |
| Former smokers, pack-years | |||||
| <10 | NA | 284 (60.7) | NA | 284 (14.7) | |
| ≥10 | NA | 184 (39.3) | NA | 184 (9.6) | |
| Current smokers, pack-years | |||||
| <10 | NA | NA | 128 (40.4) | 128 (6.6) | |
| ≥10 | NA | NA | 189 (59.6) | 189 (9.8) | |
| Smoking intensity | |||||
| Never smokers | 1141 (100) | NA | NA | 1141 (59.2) | NA |
| Former smokers, cigarettes/d | |||||
| <8 | NA | 232 (49.6) | NA | 232 (12.0) | |
| ≥8 | NA | 236 (50.4) | NA | 236 (12.3) | |
| Current smokers, cigarettes/d | |||||
| <8 | NA | NA | 144 (45.4) | 144 (7.5) | |
| ≥8 | NA | NA | 173 (54.6) | 173 (9.0) | |
| Smoking duration | NA | ||||
| Never smokers | 1141 (100) | NA | NA | 1141 (59.2) | |
| Former smokers, y | |||||
| <25 | NA | 316 (67.5) | NA | 316 (16.4) | |
| ≥25 | NA | 152 (32.5) | NA | 152 (7.9) | |
| Current smokers, y | |||||
| <25 | NA | NA | 69 (21.8) | 69 (3.6) | |
| ≥25 | NA | NA | 248 (78.2) | 248 (12.9) | |
| Recency of cessation for former smokers, y | |||||
| ≤10 | NA | 152 (32.5) | NA | 152 (7.9) | NA |
| >10 | NA | 316 (67.5) | NA | 316 (16.4) | |
| Age at smoking initiation, mean (SD), y | NA | 19.5 (5.7) | 19.2 (5.8) | 19.4 (5.8) | .47 |
| Smoking duration, mean (SD), y | NA | 19.5 (12.0) | 33.3 (11.2) | 25.1 (13.5) | <.001 |
| Smoking intensity, mean (SD), cigarettes/d | NA | 10.3 (8.5) | 9.4 (6.1) | 10.0 (7.7) | .09 |
| Alcohol consumption | |||||
| Nondrinkerb | 716 (62.8) | 263 (56.2) | 148 (46.7) | 1127 (58.5) | .001 |
| ≤3 drinks/wk | 324 (28.4) | 137 (29.3) | 103 (32.5) | 564 (29.3) | |
| >3 drinks/wk | 96 (8.4) | 67 (14.3) | 63 (19.9) | 226 (11.7) | |
| Missing | 5 (0.4) | 1 (0.2) | 3 (0.9) | 9 (0.5) | |
| BMI | |||||
| <30 | 511 (44.8) | 173 (37.0) | 160 (50.5) | 844 (43.8) | .001 |
| ≥30 | 628 (55.0) | 294 (62.8) | 156 (49.2) | 1078 (56.0) | |
| Missing | 2 (0.2) | 1 (0.2) | 1 (0.3) | 4 (0.2) | |
| BMI, mean (SD) | 31.7 (6.9) | 33.1 (7.0) | 30.9 (7.3) | 31.9 (7.0) | .001 |
| Waist-to-hip ratio | |||||
| ≤0.85 | 383 (33.6) | 110 (23.5) | 83 (26.2) | 576 (29.9) | .001 |
| >0.85 | 729 (63.9) | 348 (74.4) | 224 (70.7) | 1301 (67.5) | |
| Missing | 29 (2.5) | 10 (2.1) | 10 (3.2) | 49 (2.5) | |
| Physical activity, MET h/wk | |||||
| <11.7 | 350 (30.7) | 154 (32.9) | 131 (41.3) | 635 (33.0) | .007 |
| 11.8-37.9 | 402 (35.2) | 148 (31.6) | 91 (28.7) | 641 (33.3) | |
| ≥38 | 389 (34.1) | 163 (34.8) | 94 (29.7) | 646 (33.5) | |
| Missing | 0 | 3 (0.6) | 1 (0.3) | 4 (0.2) | |
| Physical activity, mean (SD), MET h/wk | 38.5 (49.7) | 39.1 (46.9) | 34.2 (48.2) | 37.9 (48.8) | .32 |
| Educational level | |||||
| High school graduate or less | 391 (34.3) | 181 (38.7) | 164 (51.7) | 736 (38.2) | .001 |
| Some college or vocational school | 346 (30.3) | 155 (33.1) | 104 (32.8) | 605 (31.4) | |
| Bachelor’s or graduate degree | 403 (35.3) | 132 (28.2) | 48 (15.1) | 583 (30.3) | |
| Missing | 1 (0.1) | 0 | 1 (0.3) | 2 (0.1) | |
| Household income per capita, adjusted for inflation, $ | |||||
| <15 000 | 349 (30.6) | 137 (29.3) | 144 (45.4) | 630 (32.7) | .001 |
| 15 000-29 999 | 376 (33.0) | 132 (28.2) | 97 (30.6) | 605 (31.4) | |
| ≥30 000 | 331 (29.0) | 162 (34.6) | 56 (17.7) | 549 (28.5) | |
| Unknown | 85 (7.4) | 37 (7.9) | 20 (6.3) | 142 (7.4) | |
| Insurance | |||||
| Private | 691 (60.6) | 255 (54.5) | 130 (41.0) | 1076 (55.9) | .001 |
| Medicare or Medicaid | 254 (22.3) | 153 (32.7) | 134 (42.3) | 541 (28.1) | |
| Uninsured | 115 (10.1) | 39 (8.3) | 43 (13.6) | 197 (10.2) | |
| Other or missing | 81 (7.1) | 21 (4.5) | 10 (3.2) | 112 (5.8) | |
| Marital status | |||||
| Married or living as married | 461 (40.4) | 169 (36.1) | 79 (24.9) | 709 (36.8) | .001 |
| Widow | 101 (8.9) | 69 (14.7) | 19 (6.0) | 189 (9.8) | |
| Divorced or separated | 263 (23.0) | 121 (25.9) | 84 (26.5) | 468 (24.3) | |
| Single or never married | 314 (27.5) | 107 (22.9) | 135 (42.6) | 556 (28.9) | |
| Missing | 2 (0.2) | 2 (0.4) | 0 | 4 (0.2) | |
| Estrogen receptor status | |||||
| Positive | 806 (70.6) | 324 (69.2) | 224 (70.7) | 1354 (70.3) | .63 |
| Negative | 294 (25.8) | 132 (28.2) | 89 (28.1) | 515 (26.7) | |
| Missing | 41 (3.6) | 12 (2.6) | 4 (1.3) | 57 (3.0) | |
| Tumor stage | |||||
| 0 | 195 (17.1) | 107 (22.9) | 42 (13.2) | 344 (17.9) | .001 |
| I | 408 (35.8) | 183 (39.1) | 104 (32.8) | 695 (36.1) | |
| II | 368 (32.3) | 124 (26.5) | 115 (36.3) | 607 (31.5) | |
| III and IV | 147 (12.9) | 46 (9.8) | 51 (16.1) | 244 (12.7) | |
| Missing | 23 (2.0) | 8 (1.7) | 5 (1.6) | 36 (1.9) | |
| Breast cancer subtype | |||||
| Luminal A | 538 (47.2) | 220 (47.0) | 166 (52.4) | 924 (48.0) | .38 |
| ERBB2 (formerly HER2) positive | 208 (18.2) | 65 (13.9) | 54 (17.0) | 327 (17.0) | |
| Triple negative | 191 (16.7) | 85 (18.2) | 57 (18.0) | 333 (17.3) | |
| Unknown or missing | 204 (17.9) | 98 (20.9) | 40 (12.6) | 342 (17.8) | |
| Surgery | |||||
| No surgery | 30 (2.6) | 15 (3.2) | 21 (6.6) | 66 (3.4) | .001 |
| Lumpectomy | 576 (50.5) | 267 (57.1) | 136 (42.9) | 979 (50.8) | |
| Mastectomy | 535 (46.9) | 185 (39.5) | 160 (50.5) | 880 (45.7) | |
| Unknown or missing | 0 | 1 (0.2) | 0 | 1 (0.1) | |
| Chemotherapy | |||||
| No | 495 (43.4) | 247 (52.8) | 132 (41.6) | 874 (45.4) | .001 |
| Yes | 644 (56.4) | 219 (46.8) | 184 (58.0) | 1047 (54.4) | |
| Unknown or missing | 2 (0.2) | 2 (0.4) | 1 (0.3) | 5 (0.3) | |
| Radiotherapy | |||||
| No | 376 (33.0) | 134 (28.6) | 117 (36.9) | 627 (32.6) | .04 |
| Yes | 765 (67.0) | 333 (71.2) | 196 (61.8) | 1294 (67.2) | |
| Unknown or missing | 0 | 1 (0.2) | 4 (1.3) | 5 (0.3) | |
| Hormone therapy | |||||
| No | 399 (35.0) | 169 (36.1) | 121 (38.2) | 689 (35.8) | .48 |
| Yes | 741 (64.9) | 296 (63.2) | 192 (60.6) | 1229 (63.8) | |
| Unknown or missing | 1 (0.09) | 3 (0.6) | 4 (1.3) | 8 (0.4) | |
| History of diabetes | |||||
| No | 805 (70.6) | 277 (59.2) | 209 (65.9) | 1291 (67.0) | .001 |
| Yes | 222 (19.5) | 136 (29.1) | 72 (22.7) | 430 (22.3) | |
| Unknown or missing | 114 (10.0) | 55 (11.8) | 36 (11.4) | 205 (10.6) | |
| History of hypertension | |||||
| No | 370 (32.4) | 107 (22.9) | 75 (23.7) | 552 (28.7) | .001 |
| Yes | 657 (57.6) | 306 (65.4) | 206 (65.0) | 1169 (60.7) | |
| Unknown or missing | 114 (10.0) | 55 (11.8) | 36 (11.4) | 205 (10.6) | |
| First-degree family history of breast cancer | |||||
| No | 916 (80.3) | 374 (79.9) | 255 (80.4) | 1545 (80.2) | .85 |
| Yes | 198 (17.4) | 87 (18.6) | 54 (17.0) | 339 (17.6) | |
| Missing | 27 (2.4) | 7 (1.5) | 8 (2.5) | 42 (2.2) | |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); MET, metabolic equivalent task; NA, not applicable.
a
From the χ2 test, t test, or analysis of variance when appropriate.
b
Nondrinkers defined as women who did not report drinking or drank zero alcoholic beverages per week.