Table 3 Association between proportion of night shifts and musculoskeletal pain and headaches among nurses working a 2-, 3-shift schedule or night shifts only (n = 684). Incidence rate ratio (IRR) with 95% confidence intervals (CI) and p-values from negative b

Proportion of night shifts (%)

Neck-, shoulder-, and upper back pain

  < 25

427

1.00 (ref.)

1.00 (ref.)

 25–49.9

149

0.93 (0.73, 1.17)

0.93 (0.74, 1.18)

  ≥ 50

108

0.86 (0.66, 1.13)

0.85 (0.65, 1.11)

Proportion of night shifts (%)

Low back pain

  < 25

427

1.00 (ref.)

1.00 (ref.)

 25–49.9

149

0.86 (0.65, 1.13)

0.89 (0.67, 1.17)

  ≥ 50

108

0.78 (0.57, 1.07)

0.77 (0.56, 1.05)

Proportion of night shifts (%)

Pain in the upper extremities

  < 25

427

1.00 (ref.)

1.00 (ref.)

 25–49.9

149

0.72 (0.49, 1.07)

0.79 (0.54, 1.17)

  ≥ 50

108

0.97 (0.62, 1.51)

0.90 (0.58, 1.39)

Proportion of night shifts (%)

Pain in the lower extremities

  < 25

427

1.00 (ref.)

1.00 (ref.)

 25–49.9

149

0.90 (0.68, 1.19)

0.93 (0.71, 1.22)

  ≥ 50

108

0.75 (0.55, 1.02)

0.69 (0.51, 0.94)

Proportion of night shifts (%)

Headache

  < 25

427

1.00 (ref.)

1.00 (ref.)

 25–49.9

149

1.07 (0.88, 1.29)

1.03 (0.86, 1.25)

  ≥ 50

108

0.98 (0.79, 1.22)

0.99 (0.80, 1.23)