Age-friendly shift systems - do they exist?

Introduction
Based on the age-related changes in circadian rhythms, we have hypothesized that rapidly rotating shift systems would fit better to older workers. The aim of the current study was to study the interaction of age with shift systems of different shift characteristics in relation to perceived sleep-wakefulness, mood and inflammation biomarkers.

Methods
Based on an on-going cohort study of Finnair (participation rate 56%), a questionnaire and inflammation biomarkers were analysed among 895 male workers in two age groups (-44 or 45+) . The shift systems analysed were 1-shift work (day work, n=473), 2-shift work (n=176), backward rotating 3-shift work (n=45), rapidly forward rotating 3-shift work (Respect, n=69) and "flexible" 3-shift work" (n=102). All shift workers were working in the same technical maintenance unit.

Results
Based on chi-square tests, opinions on the positive or negative effects of the used shift systems on different aspects of perceived well-being depended strongly on shift system. Respect workers, and especially the older ones, reported less negative effects than the other 3-shift workers. Based on a 2-way analysis of variance, age had significant interactions with the used shift systems showing that higher age was related with more frequent insomnia, fatigue and blood leucocytes in all other shift systems except in Respect where older workers had fewer symptoms and lower leucosyte levels than younger workers.

Discussion
Shift work and age were both associated with sleep and mood but the age trends were dependent on shift rotation. The data thus does indicate that a rapidly forward rotating shift system is a more age-friendly one compared to two other 3-shift systems with different rotation.