In the early 20th century, sociologists studying a small American city observed a division not only by class but also by daily rhythms. Working-class households typically began their day at dawn to accommodate early shifts, while business professionals tended to start later. This difference fueled a political debate in 1925 over the adoption of daylight saving time, with working-class residents opposing the change due to concerns about losing sleep and business leaders supporting it for reasons including extended daylight hours for leisure and synchronization with East Coast markets.
Nearly a century later, the tension between social and economic demands and human biological needs remains relevant. Modern research has further clarified the health consequences of disrupting natural circadian rhythms. Night-shift work, in particular, is associated with significant health risks. Studies show that most night workers cannot fully adjust their internal clocks and remain tuned to a daytime schedule, leading to chronic misalignment between their biological rhythms and sleep times. This disruption has been linked to adverse effects on blood pressure, immune function, and a heightened risk of certain cancers. Reflecting these dangers, the World Health Organization’s International Agency for Research on Cancer classifies night work as “probably carcinogenic to humans.”
Even individuals who do not work overnight but whose schedules conflict with their natural chronotype—the propensity to be a morning or evening person—may experience negative health effects. A Finnish study tracking individuals from their mid-forties into their fifties found that those with evening chronotypes were more likely to receive disability pensions over a 12-year period. Researchers suggest that conventional working hours may lead to “social jet lag,” disproportionately impacting those who naturally prefer later schedules.
The burden of disrupted work schedules remains unevenly distributed along socioeconomic lines. In the United States, night work is increasingly concentrated among individuals with no more than a high school education. Meanwhile, the shift toward remote work during the COVID-19 pandemic has mostly benefited white-collar employees, who often have more flexibility to tailor work hours to their preferences. In Europe, recent surveys show that managerial roles come with greater autonomy over work schedules, with 40 percent able to adjust their hours within limits and 19 percent exercising full control over their working time. Conversely, nearly 80 percent of lower-paid workers have their schedules fully determined by employers.
Technological advances offer potential solutions to the health and social challenges posed by night work. Automation and robotics are beginning to replace overnight human labor in some logistics sectors, with “lights-out” systems allowing robots to work unsupervised at night, reserving tasks that require human intervention for daytime shifts. The development of self-driving trucks may similarly shift long-haul driving to overnight autonomous operation, minimizing human drivers’ nighttime hours. While such shifts could improve public health by reducing circadian disruption, they also pose economic challenges for workers who currently receive higher pay premiums for night shifts, underscoring the need for careful policy planning that addresses inequality alongside technological progress.
Despite scientific concerns, political debates over time policies persist. Former U.S. President Donald Trump has advocated for making daylight saving time permanent, emphasizing leisure benefits such as extended hours for golf, signaling that the contest between economic interests and biological needs remains a contentious issue.