Characteristics of postmenopausal women with available eCRF assessment from the UK Biobank
| Characteristics | Low eCRF | Moderate eCRF | High eCRF | Standardised differences |
| Sample size, n (%) | 4558 (20.0) | 13 675 (60.0) | 4560 (20.0) | -- |
| Follow-up time (years), median (min, max) | 11.0 (0.1 to 12.0) | 11.0 (>0.0 to 12.2) | 11.0 (>0.0 to 12.1) | 3.2 |
| Age (years), median (IQR) | 61 (56–64) | 60 (56–64) | 60 (56–64) | 2.6 |
| Age categories, n (%) | ||||
| 40 to <50 | 173 (4.9) | 522 (4.9) | 174 (4.9) | 0.1 |
| 50 to <60 | 1377 (38.6) | 4133 (38.6) | 1378 (38.6) | 0.0 |
| 60 to <70 | 2000 (56.1) | 6001 (56.1) | 2001 (56.1) | 0.1 |
| >70 years | 16 (0.5) | 48 (0.5) | 17 (0.5) | 0.3 |
| BMI (kg/m2), median (IQR) | 32.4 (29.8–35.4) | 25.9 (24.1–27.9) | 22.0 (20.7–23.3) | 223.1 |
| BMI categories, n (%) | ||||
| Underweight/normal weight | 63 (1.8) | 3955 (37.0) | 3314 (92.8) | 229.5 |
| Overweight | 893 (25.0) | 5743 (53.7) | 256 (7.2) | 76.2 |
| Obesity | 2610 (73.2) | 1006 (9.4) | 0 (0.0) | 120.1 |
| Body fat percentage, median (IQR) | 44.1 (41.2–46.9) | 36.9 (33.6–39.9) | 29.5 (26.0–32.5) | 212.6 |
| Body fat percentage categories | ||||
| 1st quintile (<20th percentile) | 26 (0.7) | 1289 (12.0) | 2276 (63.8) | 118.7 |
| 2nd quintile (>20th to 40th percentile) | 63 (1.8) | 2562 (23.9) | 944 (26.4) | 50.6 |
| 3rd quintile (>40th to 60th percentile) | 240 (6.7) | 2973 (27.8) | 284 (8.0) | 38.8 |
| 4th quintile (>60th to 80th percentile) | 859 (24.1) | 2709 (25.3) | 64 (2.0) | 48.8 |
| 5th quintile (>80th percentile) | 2378 (66.7) | 1171 (10.9) | 2 (0.1) | 129.4 |
| Ethnicity | ||||
| White | 3304 (92.7) | 9955 (93.0) | 3243 (90.8) | 5.3 |
| Black | 151 (4.2) | 203 (1.9) | 33 (0.9) | 14.3 |
| Other* | 111 (3.1) | 546 (5.1) | 294 (8.2) | 15.0 |
| Education, n (%) | ||||
| Less than postsecondary† | 898 (25.2) | 2727 (25.5) | 873 (24.5) | 1.6 |
| Postsecondary‡ | 2080 (58.3) | 6402 (59.8) | 2220 (62.2) | |
| Missing§ | 420 (11.8) | 1264 (11.8) | 380 (10.6) | 5.8 |
| Family history of breast cancer (yes)¶, n (%) | 527 (11.6) | 1599 (11.7) | 493 (10.8) | 2.5 |
| Age at menarche (years), median (IQR) | 13.0 (11.0–14.0) | 13.0 (12.0–14.0) | 13.0 (12.0–14.0) | 14.7 |
| Parous (yes), n (%) | 2882 (80.8) | 8784 (82.1) | 2750 (77.0) | 8.3 |
| No of live births, median (IQR) | 2 (1–2) | 2 (1–2) | 2 (1–2) | 9.0 |
| No of live births category, n (%) | ||||
| Nulliparous | 684 (19.2) | 1920 (17.9) | 820 (23.0) | 8.3 |
| One | 474 (13.3) | 1334 (12.5) | 466 (13.1) | 1.7 |
| Two | 1529 (42.9) | 4975 (46.5) | 1544 (43.3) | 4.8 |
| Three or more | 879 (24.7) | 2475 (23.1) | 740 (20.7) | 9.3 |
| Age at first birth**, n (%) | ||||
| <20 | 265 (11.0) | 620 (8.3) | 165 (7.2) | 7.9 |
| 20 to <25 | 870 (36.2) | 2361 (31.7) | 602 (26.4) | 12.5 |
| 25 to <30 | 920 (38.3) | 2980 (40.0) | 968 (42.5) | 3.1 |
| 30 to <35 | 283 (11.8) | 1198 (16.1) | 434 (19.0) | 9.4 |
| >35 | 66 (2.8) | 286 (3.8) | 110 (4.8) | 5.3 |
| Hormone replacement therapy use, n (%) | 71 (2.0) | 237 (2.2) | 73 (2.0) | 1.0 |
| Smoking status, n (%) | ||||
| Never | 1540 (43.2) | 4637 (43.3) | 1612 (45.2) | 2.6 |
| Current | 243 (6.8) | 671 (6.3) | 263 (7.4) | 2.9 |
| Previous | 1783 (50.0) | 5396 (50.4) | 1695 (47.5) | 3.9 |
| Alcohol frequency, n (%) | ||||
| Never | 386 (10.8) | 833 (7.8) | 353 (9.9) | 7.0 |
| Special occasions only | 739 (20.7) | 1472 (13.8) | 472 (13.2) | 13.4 |
| 1–3 times a month | 542 (15.2) | 1274 (11.9) | 359 (10.1) | 10.4 |
| Once or twice a week | 839 (23.5) | 2658 (24.8) | 809 (22.7) | 3.4 |
| 3 or 4 times a week | 623 (17.5) | 2386 (22.3) | 824 (23.1) | 9.3 |
| Daily | 437 (12.3) | 2081 (19.4) | 753 (21.1) | 15.9 |
| MET-minutes per week††, median (IQR) | 1473 (693.0–3013) | 1908.0 (959.0–3657.0) | 2228.5 (1092.0–4266.0) | 20.7 |
| Protocol | ||||
| 1 (minimal risk)‡‡ | 2797 (78.4) | 9162 (85.6) | 3188 (89.3) | 19.9 |
| 2 (small risk)§§ | 560 (15.7) | 1195 (11.2) | 309 (8.7) | 14.5 |
| 3 (medium risk)¶¶ | 209 (5.9) | 347 (3.2) | 73 (2.0) | 13.2 |
| Exposure | ||||
| VO2peak (mL/kg/min), mean±SD | 16.9±1.1 | 20.5±1.2 | 24.3±1.5 | 378.8 |
| Outcome | ||||
| Breast cancer, n (%) | 115 (3.2) | 329 (3.1) | 85 (2.4) | 3.4 |
| Other cancer, n (%) | 349 (9.9) | 967 (9.0) | 307 (8.6) | 2.7 |
| Death, n (%) | 69 (1.9) | 109 (1.0) | 63 (1.8) | 5.1 |
| Crude incident rates for breast cancer (per 10 000 person-years) | 31.0 | 29.4 | 22.7 | -- |
Standardised differences greater than 10% are bolded to indicate clinically meaningful differences. One standardised difference was calculated by first calculating a unique standardised difference for all possible pairwise. Standardised differences less than 0 were multiplied by −1, and then the average of the three standardised differences was calculated.
*Asian, mixed, other and missing.
†Advanced levels, advanced subsidiary levels or equivalent; ordinary levels, general certificate of secondary education or equivalent; certificate of secondary education or equivalent.
‡College or university; national vocational qualification, higher national diploma, higher national certificate or equivalent; other professional qualification (eg, teacher, nurse).
§None of the above or missing.
¶Self-reported history of their father, mother, sister and/or brother having had breast cancer.
**Low fit n=4418, moderate fit n=13 766, high fit n=4212.
††Three types of physical activity were self reported using the modified version of the IPAQ short form: walking, moderate and vigorous physical activity. Data were cleaned using standardised procedures, and then minutes of physical activity were multiplied by corresponding MET values for walking (3.3 METs), moderate (4.0 METs) and vigorous (8.0 METs) physical activity to determine total weekly METs of physical activity.
‡‡Participants who complete protocol 1 (aka minimal risk) for the eCRF assessment work at a maximum of 50% of their predicted workload.
§§Participants who complete protocol 2 (aka small risk) for the eCRF assessment work at a maximum of 35% of their predicted workload
¶¶Participants who complete protocol 3 (aka medium risk) for the eCRF assessment worked at a constant workload
%, per cent; BMI, body mass index; eCRF, estimate cardiorespiratory fitness; IQR, interquartile range; max, maximum; min, minimum; n, sample size; SD, standard deviation.