Numerous cross-sectional studies report high prevalence rates of sleepiness and insomnia in shift workers, but few longitudinal studies exist. We investigated trajectories of sleepiness and insomnia symptoms in a sample of Norwegian nurses across four measurements, spanning a total of four years (sleepiness) and five years (insomnia). The participants completed the Epworth Sleepiness Scale and the Bergen Insomnia Scale at each measurement instance. Latent growth curve models were used to analyse the data. Separate models examined night work (night work, entering and leaving night work) and rotational work (rotational work, entering and leaving rotational work) as predictors for trajectories of sleepiness and insomnia symptoms, respectively. Baseline values of sleepiness and insomnia were higher among rotational shift workers than among workers with fixed shifts (day or night). The results showed that night work throughout the period and entering night work during the period were not associated with different trajectories of sleepiness or insomnia symptoms, compared to not having night work. The same results were found for rotational work and entering rotational work, compared to not having rotational work. Leaving night work and leaving rotational work were associated with a decrease in sleepiness and insomnia symptoms, compared to staying in such work.
Keywords: Insomnia; night work; shift work; sleepiness.