Unveiling the Night Shift – Examining Shift Work’s Affect on Adult Health

Dr. Durdana Khan

Shift work is under scrutiny once again as a comprehensive study sheds light on its effects on the health of workers. While shift work keeps industries running 24/7, it has long been associated with a slew of health issues, including sleep disturbances, accidents, mood and mental health disorders, and even serious long-term conditions such as cardiovascular diseases, cancer, diabetes and peptic ulcers.

A recent study using data from the Canadian Longitudinal Study on Aging (CLSA) and published in the Journal of Occupational and Environmental Medicine reveals its connection to frailty among middle-aged and older adults. Frailty, characterized by reduced strength, endurance, and physiological function, can increase vulnerability and dependency in older individuals.

Shift work includes any work done outside the regular daytime hours of 9am-5pm and comes in various forms, with regular evening and night shifts starting after 3 p.m. and 11 p.m. Rotating shift work involves schedules that switch between daytime, evening, and night shifts.

Nearly one in every five individuals reported exposure to some form of shift work during their careers. Sectors with a higher propensity for shift work include protective service workers, healthcare workers, sales and service workers, and primary industry laborers, such as farm workers.

The study, which analyzed data from 47,000 Canadian adults, uncovered alarming associations between shift work and frailty, particularly among female workers.

Increased Risk of Frailty

Both male and female workers exposed to shift work faced an increased risk of frailty over a three-year follow-up period when compared to daytime workers. For female workers, rotating shift work in their longest-held jobs was associated with higher odds of being classified as frail.

Several factors may contribute to the heightened frailty risk among shift workers. Disruptions in circadian rhythms, governed by the body's internal clock located in the hypothalamus, can lead to metabolic, hormonal, and inflammatory disturbances.

Shift work has been linked to conditions — such as circadian misalignment — that can lead to disease. Graphic courtesy of the CLSA

This disruption can result from exposure to light during nighttime hours, as well as suppressed production of melatonin, a hormone crucial for sleep induction. Furthermore, cortisol, typically secreted during the daytime, becomes elevated at night in shift workers, exacerbating the circadian imbalance. Collectively, these physiological disruptions form a complex web of potential risk factors associated with shift work.

Behavioral factors, such as unhealthy eating habits, reduced physical activity, higher rates of smoking, and increased alcohol consumption, have also been linked to shift work. Social isolation can further compound the negative effects on workers' well-being.


Steps can be taken to mitigate the health risks associated with shift work, such as raising awareness to help workers make informed choices about their careers and lifestyles. Employers and organizations also have a role to play, offering health promotion programs, health surveillance, and work fitness evaluations.

Organizations should strive to design shift work schedules that minimize disruption to circadian rhythms. Shift workers' health should not be compromised in the name of productivity and convenience.

Samantha Paul, associate editor
This article is based portions of a Sept. 19 webinar by Dr. Durdana Khan MD, MPH; York University, Toronto, Ontario, Canada; hosted by the Canadian Longitudinal Study on Aging (clsa-elcv.ca).