KLOKWERK – a cross-sectional study of the effects of working at night

While we know that working at night has a potential effect on human health, we don’t know which specific aspects related to working at night are most deleterious. Finding this out is the goal of the Klokwerk study.

Long-term occupation in a profession requiring night-shift work has been reported to increase the risk of adverse human health effects. Although it is well known that night-shift work disrupts lifestyle and circadian rhythm, the biological mechanism through which adverse health effects primarily occur remains largely unknown. One aspect complicating studying the potential health effects of night-shift work is its complex mixture of dimensions which independently or combined can have an effect on human health. Accurate measurements of these night-shift work dimensions will give us insight in what exposure to night-shift work entails. In addition, linking measurements of the night-shift work dimensions to measurements of early biological perturbations  and intermediate health outcomes will provide clues to identify which aspects of night work are most detrimental to health (reflect most disruptions in biomarkers).

This study aims at, first, assessing the most relevant exposure aspects of night-shift work and, second, identifying biomarkers for both acute and chronic circadian disruption associated to these specific night-shift work aspects. By applying detailed questionnaires and objective monitors we will be able to quantify specific aspects of the complex mixture of exposures together defined as ‘night-shift work’. We will associate these aspects with intermediate health outcomes, including known biomarkers of circadian disruption, to identifying which aspects contribute most to biological perturbations.

KLOKWERK is a cross-sectional study among approximately 150 female nurses, both nurses who regularly conduct night-shift work and nurses that do not work in night-shifts. In addition to questionnaires and objective assessments of exposure (sensors), biological samples (hair, urine, blood, feces) is collected.

“We can’t abolish working at night, but we should search for ways to minimize its impact on workers’ health” – Jelle Vlaanderen