Table 5.
Farm exposures and risk of incident hyperthyroidism in AHS spouses.
| Exposure | Unexposed cases | Exposed cases | HR (95% CI)a | HR (95% CI)b |
|---|---|---|---|---|
| Lived at least half the life on a farm before 18 | ||||
| Age ≤ 60c | 163 | 166 | 0.78 (0.63, 0.98) | – |
| Age > 60c | 50 | 135 | 1.10 (0.79, 1.52) | – |
| Living on a farm 10 years ago | 104 | 415 | 0.88 (0.69, 1.10) | – |
| No. of years lived on a farm (years)d | ||||
| 0–31 | 263 | Ref | ||
| > 31 | 249 | 0.89 (0.73, 1.08) | – | |
| Worked in the field recent growing season | ||||
| No | 242 | Ref | Ref | |
| < 10days | 96 | 0.92 (0.72, 1.17) | 0.95 (0.71, 1.27) | |
| 10–30 days | 102 | 1.11 (0.88, 1.40) | 1.02 (0.73, 1.42) | |
| 31–100 days | 59 | 0.98 (0.73, 1.31) | 0.91 (0.59, 1.40) | |
| > 100 days | 14 | 0.90 (0.52, 1.56) | 0.56 (0.24, 1.31) | |
| Tasks in the last growing season | ||||
| Till soil | 385 | 124 | 1.02 (0.82, 1.26) | 0.96 (0.75, 1.24) |
| Planting | 373 | 137 | 1.11 (0.90, 1.38) | 0.91 (0.68, 1.21) |
| Apply natural fertilizer | 444 | 62 | 0.98 (0.75, 1.29) | 0.80 (0.58, 1.09) |
| Apply chemical fertilizer | 427 | 81 | 1.47 (1.15, 1.90) | 1.58 (1.16, 2.17) |
| Drive combines | 448 | 57 | 1.06 (0.80, 1.41) | – |
| Handpick crops | 360 | 147 | 1.14 (0.93, 1.40) | 1.11 (0.86, 1.42) |
| Other tasks, at least monthly | ||||
| Milk cows | 487 | 10 | 0.58 (0.31, 1.08) | – |
| Grind animal feed | 469 | 24 | 0.82 (0.54, 1.24) | – |
| Veterinary procedures | 432 | 66 | 1.05 (0.80, 1.37) | – |
| Drive trucks | 293 | 207 | 1.15 (0.96, 1.38) | – |
| Drive diesel tractor | 335 | 167 | 1.02 (0.84, 1.24) | 1.08 (0.83, 1.40) |
| Drive gasoline tractor | 375 | 123 | 0.93 (0.75, 1.15) | 0.87 (0.68, 1.12) |
| Repair engines | 486 | 14 | 2.23 (1.31, 3.82) | 2.14 (1.15, 3.98) |
| Grind metal | 488 | 10 | 1.66 (0.88, 3.11) | -e |
| Clean with gasoline | 413 | 83 | 1.15 (0.90, 1.47) | 1.13 (0.84, 1.51) |
| Clean with solvents | 399 | 102 | 1.04 (0.83, 1.30) | 0.86 (0.64, 1.15) |
| Paint | 327 | 173 | 1.13 (0.94, 1.37) | 1.15 (0.90, 1.47) |
| Hours/day in the sun, recent growing season | ||||
| Up to 1h | 112 | Ref | ||
| 1–5 h | 233 | 0.90 (0.71, 1.13) | – | |
| >6h | 52 | 0.96 (0.68, 1.34) | – | |
| Hours/day in the sun, 10years ago | ||||
| Up to 1 h | 59 | Ref | ||
| 1–5 h | 230 | 1.19 (0.89, 1.59) | – | |
| >6h | 82 | 1.11 (0.79, 1.57) | – |
Abbreviation: CI, confidence interval; HR, hazard ratio.
a
Adjusted for education, state, smoking, and ever mixed or applied pesticides.
b
Adjusted for education, state, smoking, and correlated farm exposures; entry “-” indicates exposures either not correlated with other farm exposures (exposed and unexposed n may differ due to missing values in correlated exposures).
c
Hazard ratio allowed to vary by the median age (i.e., 60 years) for pesticides that did not meet proportional hazards assumptions (p ≤ 0.10).
d
Different cut-off used for “no. of years lived on a farm” for hyperthyroidism than hyperthyroidism.
e
Not sufficient n for HR to vary by the median age.