Table 1.
Basic characteristics of study participants at their first endoscopy in three cohort studies (NHS, NHS2 and HPFS) a
| Non-polyps | Conventional adenomas | Serrated polyps | |
|---|---|---|---|
| No. of participants | 112,107 | 6,161 | 5,918 |
| Age, year | 57±10 | 59±10 | 57±9 |
| Age<50 years, % | 20 | 14 | 19 |
| Female, % | 87 | 77 | 85 |
| Year of endoscopy, % | |||
| Before 1995 | 18 | 10 | 8 |
| 1995-2000 | 22 | 22 | 21 |
| 2000-2005 | 28 | 35 | 41 |
| After 2005 | 32 | 32 | 30 |
| Reason for first endoscopy, % | |||
| Symptom | 29 | 31 | 29 |
| Routine screening | 67 | 62 | 65 |
| Unknown | 4 | 7 | 6 |
| Number of surveillance endoscopy, % | |||
| 0 | 24 | 9 | 10 |
| 1 | 28 | 20 | 21 |
| 2 | 19 | 22 | 22 |
| >2 | 29 | 49 | 47 |
| Family history of colorectal cancer, % | 16 | 21 | 22 |
| Pack-years of smoking | 8.0±14.5 | 9.9±16.4 | 12.3±17.9 |
| Current smoking status, % | |||
| Never smokers | 56 | 51 | 45 |
| Past smokers | 38 | 40 | 42 |
| Current smokers | 6 | 9 | 13 |
| Body mass index, kg/m2 | 26.7±5.6 | 27.2±5.7 | 27.6±5.8 |
| Physical activity, MET-hours/week b | 21.9±26.9 | 20.8±25.5 | 20.3±24.0 |
| Alcohol intake, g/day | 5.7±10.0 | 6.6±11.1 | 7.1±11.9 |
| Regular aspirin use, % c | 26 | 26 | 27 |
| Number of polyps | |||
| 1-2, n (%) | 5,543 (90) | 4,957 (84) | |
| ≥3, n (%) | 599 (10) | 579 (10) | |
| Missing, n (%) | 19 (0) | 382 (6) | |
| Size of polyps | |||
| <10mm, n (%) | - | 3,902 (63) | 5,010(85) |
| ≥10mm, n (%) | - | 1,985 (32) | 566(10) |
| Missing, n (%) | 274 (5) | 342 (5) | |
| Location of polyps | |||
| Proximal colon, n (%) | - | 1,975 (32) | 1,347 (23) |
| Distal colon, n (%) | - | 2,448 (40) | 1,968 (33) |
| Rectum, n (%) | - | 763 (12) | 1,530 (26) |
| More than one region, n (%) | 964 (15) | 915(15) | |
| Missing, n (%) | 11 (0) | 158 (3) | |
| Histology | |||
| Tubular adenoma, n (%) | - | 4,622 (75) | - |
| Tubulovillous adenoma, n (%) | - | 1,145 (19) | - |
| Villous adenoma, n (%) | - | 228 (4) | - |
| Adenoma with high-grade dysplasia, n (%) | - | 166 (2) | - |
Abbreviations: NHS, the Nurses’ Health Study; NHS2, the Nurses’ Health Study 2; HPFS, the Health Professionals Follow-up Study; MET, metabolic equivalent task.
The presented data are based on baseline information for each participant at their first endoscopy. Variables including current smoking status, body mass index, physical activity, alcohol intake and regular aspirin use, are adjusted for age and sex. Mean ±SD is presented for continuous variables and number of participants (percentage) for categorical variables.
Physical activity is represented by the product sum of the MET of each specific recreational activity and hours spent on that activity per week.
A standard tablet contains 325 mg aspirin, and regular users were defined as those who used at least two standard tablets per week.