Table 2

The association between shift work/number of weekly working hours and the incidence of dementia. Associations are expressed as IRR and their 95% CIs.

Dementia
cases
Person-
years
Model 1
(main analysis)
Model  2
(supplementary analysis)
Model 3
(supplementary analysis)
IRR95% CIIRR95% CI
Shift work
 Day work (reference)6927 9751.001.001.00
 Shift work (−night work)838280.900.44 to 1.850.810.39 to 1.680.880.42 to 1.84
 Shift work (+night work)*610562.010.87 to 4.651.920.81 to 4.572.110.92 to 4.85
Weekly working hours
 37 hours/week (reference)3716 2801.001.001.00
 ≤27 hours/week1249831.130.53 to 2.431.130.53 to 2.401.130.53 to 2.42
 28–36 hours/week1445391.770.90 to 3.491.690.87 to 3.291.700.86 to 3.36
 38–44 hours/week1435492.081.11 to 3.902.051.08 to 3.891.981.03 to 3.79
 ≥45 hours/week840820.990.47 to 2.110.970.45 to 2.081.040.49 to 2.22
  • Model 1: Gender, age, time since exposure assessment, calendar year and duration of vocational education. Model 2: Model 1 + ruminations about work, influence at work and possibilities for development. Model 3: Model 1 + smoking, BMI and hypertension.

  • *Permanent night work analysed separately: IRR=3.25; 95% CI 1.35 to 7.83 (model 1), IRR=3.48; 95% CI 1.45 to 8.35 (model 2), IRR=3.62, 95% CI 1.53 to 8.55 (model 3).

  • IRR, incidence rate ratios.