Dix ans d’étude sur plus de 3 000 travailleurs et retraités du sud de la France conclue que travailler de nuit ou en horaire décalé (en quart de travail irréguliers) est nocif pour les capacités cognitives.
The short-term effects on the health of the night or shift workers are fairly well documented. Employees are often diagnosed with multiple health problems such as having ulcers, cardiovascular diseases, metabolic syndromes, breast cancer or even reproductive problems. Working the night shift is also less safe and turns out to be less productive.
On the other hand, less known impacts of night shifts or offset working hours are long-term health effects, specifically on cognition. That is why, in 1996, a team of researchers from the National Centre for Scientific Research (CNRS) in Toulouse recruited 3,232 workers and retirees who were either 32, 42, 52 or 62 years of age to participate in the experiment. Half of these participants were working or had worked at least 50 days in unsocial hours.
Three times in 15 years, once at the beginning of the study in 1996, then five and ten years later (2001 and 2006), the participants underwent neuropsychological tests measuring their reaction time as well as their attention and memory span.
Cognitive decline
The study’s results show that employees who had worked odd hours for 10 or more years were victims of a greater cognitive decline than their counterparts.
According to the participants’ scores, cognitive aging is visible six and a half years earlier among evening workers than their peers, results “that are not negligible,” but that are yet to be confirmed through a replicate study, states Jean-Claude Marquié, one of the study’s lead coordinators, in an interview published in Le Monde.
In addition to direct impacts on cognition, researchers noted that there was a “wide variation” between individuals, which is why Marquié offers “personalized medical supervision.” The expert’s other recommendation: adjusting schedules according to what is most conducive to sleep. “It is better, for example, to start at six in the morning than at four,” he says.
Lighting, another solution
As if it was permanent jet lag, night workers suffered from a disrupted biological clock. By coming home from work and going straight to bed, the individual wanders into a world where the sun is at its peak.
In a context where night work is stable over a long period of time, some adaptation is possible. However, if shifts are irregular, the circadian rhythm is completely misbalanced. Internal cycles and outside clues simply cannot coordinate.
The employer holds some solutions. By increasing the lighting in the workplace, the night worker’s biological clock is deceived through limited exposure to night light. Tests on nurses working night shifts in Quebec displayed convincing results.
Anabel Cossette Civitella – 37th AVENUE