TABLE 4.
Repeated-Measures Model* Association Between Mean Work Rate in Counts per Minute and Worker Characteristics
| Covariate | Estimate | 95% CI | P |
|---|---|---|---|
| Wet bulb globe temperature centered around 25°C (mean, 0.06°C) | −4.34 | −7.09 to −1.59 | 0.002 |
| Quarter hours worked since 4 am centered around 29 (11:15 am) | 2.13 | 0.82 to 3.45 | 0.0014 |
| Gender (male reference) | <0.0001 | ||
| Pay type (hourly reference vs piece rate) | <0.0001 | ||
| Female × piece rate pay interaction | 0.0011 | ||
| Age centered around 38 y (mean, 0.5 y) | −3.64 | −4.50 to −2.79 | <0.0001 |
| BMI (BMI <25 reference vs BMI ≥25 kg/m2) | 0.0004 | ||
| Female × BMI ≥25 kg/m2 interaction | 0.0021 | ||
| Dehydration | 51.37 | 19.24 to 83.50 | 0.0018 |
BMI, body mass index; CI, confidence interval.
*Regression model for repeated-measures data with worker quarter-hour intervals as units of analysis was fit using SAS PROC MIXED with within-subject first-order autoregressive structure for residuals. Estimated autocorrelation was 54%.