Self-assessed threshold for cold temperatures and thermal insulation of clothing among poultry workers

The association between self-assessed cold threshold (CT) and thermal insulation of clothing (I_cl) was analysed in 283 poultry workers in Thailand. The mean CT was 13.5 °C (range - 28-29) and the mean I_cl was 1.23 clo (range 0.35-2.21). The adjusted CT remained unchanged at low I_cls (0.35 through 1.25 clo) but was estimated to increase by 14.8 °C at high I_cls (1.25 through 2.21 clo). Overall, CT was higher by 2.4 °C (95% confidence interval [CI] 0.3-3.8) at high (≥ 1.25 clo) than that at low (< 1.25 clo) I_cl, but this difference was modified by personal and work-related factors. The difference was 2.6 °C (CI 0.5-4.6) for older (30-57 y) compared to younger (18-29 y) participants, with an excess of 7.3 °C (CI 5.6-9.0) for low vs high educated participants, 2.6 °C (CI 0.5-4.8) for those doing heavy vs light work, 7.4 °C (CI 3.7-11.0) for alcohol consumers vs others, and 3.4 °C (CI 0.6-6.3) for smokers vs non-smokers. The differences were independent of personal characteristics and worksite physical conditions and were interpreted as increased cold sensitivity among subgroups with lesser stamina and poorer health. Sensitive worker subgroups should be identified, and their need for cold protection should be reviewed.