Table 2

Predictors of long working hour injuries occurring 9 or more hours into a shift. Multivariable logistic regression model* based on all reported injuries to MSHA Part 50 Program in U.S.: 1983–2015

Adjusted OR
(95% CI)
Year of accident (1983–2015)1.02 (1.02 to 1.02)<0.001
Day of week of accident: sunday1.23 (1.17 to 1.28)<0.001
Less than 2 years of experience at current mine site1.13 (1.11 to 1.15)<0.001
Irregular shift start†2.85 (2.78 to 2.92)<0.001
Employed by a contractor (not operator)1.64 (1.59 to 1.69)<0.001
Canvass or class of commodity mined (based on industry code)
 Anthracite and bituminous coalRef
 Metal1.52 (1.48 to 1.56)<0.001
 Non-metal1.22 (1.17 to 1.26)<0.001
 Sand and gravel1.71 (1.66 to 1.77)<0.001
 Stone1.56 (1.52 to 1.59)<0.001
Mechanism or activity at time of accident
 Ambient temperature heat related: atmosphere or environment1.96 (1.66 to 2.30)<0.001
 Fall from: headframe, derrick, tower, ladder, machine, vehicle, equip, piled material, scaffolds, walkways and platforms.1.25 (1.21 to 1.30)<0.001
 Flash burns (welding)2.08 (1.85 to 2.33)<0.001
 Caught in/between/under running meshing objects, struck by flying objects and struck against moving objects while the employee conducting maintenance or repairs1.24 (1.13 to 1.35)<0.001
 Mine fire1.74 (1.09 to 2.77)0.021
Injury occurred offsite‡1.32 (1.12 to 1.54)<0.001
Employee was not working at their regular job at time of injury§0.89 (0.85 to 0.94)<0.001
Mine size category (average number of employees in year of accident)
 Less than 201.52 (1.48 to 1.57)<0.001
 20–491.33 (1.30 to 1.37)<0.001
 50–991.17 (1.14 to 1.21)<0.001
 100–1990.99 (0.96 to 1.02)0.625
 200 or moreRef
  • *All the variables in the table represent the variables included in the final multivariable model. Sex and age were insignificant in the final multivariable model and were excluded.

  • †Based on MSHA data, most shifts start in specific windows of time in the morning, afternoon and evening shifts (92.2%). We accounted for irregular start times for each shift including shifts beginning between 00:31–05:29, 08:31–13:29 and 16:31–21:29, allowing for workers to arrive 30 min early or late for shifts in the morning (06:00–08:00), afternoon shifts (14:00–16:00) and night (22:00–00:00).

  • ‡These include injuries to employees off of the mine property.

  • §These are workers whose regular job title was different from the job title they were working at the time of injury.

  • MSHA, Mine Safety and Health Administration.