Table 1. Characteristics of study participants at enrollment*.
| Variables | AHS swine-exposed, no. (%), n = 707 | AHS nonswine-exposed, no. (%), n = 80 | University controls, no. (%), n = 79 |
|---|---|---|---|
| Sex† | |||
| Male | 455 (64.4) | 3 (3.8) | 26 (32.9) |
| Female | 252 (35.6) | 77 (96.3) | 53 (67.1) |
| Age group, y | |||
| 24–45 | 71 (10.0) | 19 (23.8) | 56 (70.9) |
| 46–54 | 179 (25.3) | 22 (27.5) | 13 (16.5) |
| 55–89 | 457 (64.6) | 39 (48.8) | 10 (12.7) |
| Mean age‡ |
56 |
51.1 |
35.3 |
| Received influenza vaccine in the past 4 y | |||
| Yes | 392 (55.5) | 43 (53.8) | 44 (55.7) |
| No/unsure | 315 (44.6) | 37 (46.3) | 35 (44.3) |
| Swine influenza vaccine in 1976* | |||
| Yes | 62 (8.8) | 4 (5.0) | 1 (1.3) |
| No | 506 (71.6) | 53 (66.3) | 78 (98.7) |
| Unsure | 132 (18.7) | 22 (27.5) | 0 |
| Missing |
7 (1.0) |
1 (1.3) |
0 |
| Currently work with nursery or finishing swine | |||
| Nursery swine | 18 (2.6) | 0 | – |
| Finishing swine | 126 (17.8) | 0 | – |
| Both | 168 (23.8) | 0 | – |
| No | 391 (55.3) | 80 (100.0) | – |
| Missing |
4 (0.6) |
0 |
|
| Years worked in swine production | |||
| Never | 0 | 76 (95.0) | – |
| <1 | 1 (0.1) | 0 | – |
| 1–4 | 10 (1.4) | 0 | – |
| 5–10 | 38 (5.4) | 0 | – |
| >10 | 650 (91.9) | 0 | – |
| Missing |
8 (1.1) |
4 (5.0) |
|
| On average, how often do you see or touch swine, other than the swine on the farm where you work? | |||
| Never | 270 (38.2) | 49 (61.3) | – |
| Rarely | 344 (48.7) | 24 (30.0) | – |
| Monthly | 27 (3.8) | 0 | – |
| Weekly | 27 (3.8) | 0 | – |
| Every day | 14 (2.0) | 1 (1.3) | – |
| Missing |
25 (3.5) |
6 (7.5) |
– |
| How long have you lived on this or other swine farm? | |||
| Never | 15 (2.1) | 18 (22.5) | – |
| <1 y | 1 (0.1) | 1 (1.3) | – |
| 1–4 ys | 4 (0.6) | 2 (2.5) | – |
| 5–10 y | 18 (2.6) | 8 (10.0) | – |
| >10 y | 636 (90.0) | 42 (52.5) | – |
| Missing |
33 (4.7) |
9 (11.3) |
– |
| Work in a slaughterhouse or meat processing plant | |||
| Yes | 4 (0.6) | 2 (2.5) | – |
| No | 674 (95.3) | 75 (93.8) | – |
| Missing | 29 (4.1) | 3 (3.8) | – |
*AHS, Agricultural Health Study; AHS swine-exposed, participants from the A HS who reported working in swine production; AHS nonswine-exposed, participants from the AHS who denied ever working in swine production (96.3% female and among these females 75.5% were spouses of the AHS swine–exposed); university controls, faculty, staff, and students from the University of Iowa who denied ever working in swine production. †Statistically significant considering a 95% confidence level by Fisher exact test for the 3 groups. ‡Statistically significant considering a 95% confidence level by analysis of variance test for the 3 groups.