Modern society operates around the clock, with more than 20% of workers engaged in shift work. These nonstandard working hours, often falling outside the typical 7:00 AM to 6:00 PM timeframe, are essential for sectors like healthcare, transportation, and protective services [1]. However, this round-the-clock demand frequently creates a conflict between imposed work schedules and individuals’ natural biological rhythms, known as circadian rhythms [2–4]. A central feature of shift work is the disruption of circadian rhythms, a state of misalignment between physiological functions and imposed sleep-wake behavior [4]. The disruption of these rhythms is associated with a wide array of negative health consequences, including sleep disorders, gastrointestinal issues, metabolic disorders, certain neoplasms, immune diseases, and mood disorders like depression and anxiety [5]. It can also lead to cognitive abnormalities such as poor concentration and memory.

Adding another layer of complexity is the inherent variability in human circadian timing, characterized by individual chronotypes [6,7]. Chronotype describes an individual’s preference for sleep and activity times and is largely influenced by genetics, development, and environmental light. Chronotypes exist on a continuum, ranging from extreme morning types who prefer early sleep and wake times to extreme evening types (“Night Owls”) who naturally stay up and wake up later. While most people fall into an intermediate category, approximately 40% lean towards one of the extreme types. This perspective explores the question of whether the evening chronotype is better adapted to the demands of a 24/7 world or if they remain significantly at risk.

Circadian misalignment occurs when an individual’s preferred sleep-wake cycle clashes with their imposed schedule. This is evident when evening chronotypes must wake early for day shifts or when morning chronotypes work night shifts. The resulting disconnect, sometimes referred to as social jetlag (the difference in mid-sleep time between workdays and free days), is considered a measure of circadian disruption and is linked to sleep debt and chronic health conditions [8]. A significant portion of the population experiences at least one to two hours of social jetlag, highlighting the widespread impact of schedules misaligned with biology.

Shift work, particularly night shifts, directly opposes the body’s natural inclination to be alert during the day and sleep at night. Sleeping during the biological day often results in shorter, poorer quality sleep, hindering full recovery. The sources highlight that chronotype significantly modulates how individuals tolerate different shifts [9]. Earlier chronotypes experience greater constraints on sleep (shorter duration, reduced quality, high social jetlag) during night shifts, while later chronotypes face similar issues during early morning shifts. Social jetlag is generally highest for night shifts [10].

Given the challenges of night work for morning types, it has been hypothesized that evening types might be better suited for these shifts [11]. Some evidence supports this, suggesting that frequent night shifts are indeed better tolerated by very late chronotypes. Sleep during and after evening shifts is also least influenced by social constraints, potentially allowing individuals to sleep closer to their “circadian sleep window.” One study even found that fixed night shift workers perceived less sleep deprivation compared to those on rotating shifts, suggesting that adaptation might be possible when an atypical schedule is consistent. Shift work can, in theory, provide “temporal niches” that allow different chronotypes to sleep according to their internal timing, which could be an opportunity within the necessary structure of a 24/7 society.

The assumption that evening types are inherently “adapted” to the demands of a 24/7 world, particularly shift work, is increasingly challenged by empirical evidence. Although evening types may demonstrate comparatively better tolerance for night shifts than morning types, this does not imply that they are free from risks or genuinely well-adapted to such schedules.

Several sources indicate that evening chronotype itself is associated with a higher general risk for various noncommunicable diseases, irrespective of shift work [12]. Furthermore, evening types are specifically linked to adverse metabolic profiles. They exhibit higher fat mass and lower lean mass compared to morning types, independent of obesity status. Late chronotypes show significantly higher visceral adiposity index, liver fat, and hepatic steatosis.

The practice of being awake and potentially eating during biological night (common for evening types or shift workers) can increase appetite and food intake, contributing to obesity. Eating at unusual times, as seen in evening types, may disrupt the body’s normal metabolism [7]. The loss of coordination between the biological and peripheral clocks in evening types can disturb energy balance [7].

When evening chronotypes engage in shift work, particularly schedules that include early morning shifts or fast rotations, they still experience significant disruption [13]. Evening types are more sensitive to insomnia and report poorer sleep quality compared to morning types when exposed to shift work demands [14]. The combination of evening chronotype and ever having worked shifts is associated with a significantly higher risk of poor mental health compared to day workers. While one study found morningness was inversely correlated with poor mental health in shift workers, highlighting vulnerability in evening types, another suggested chronotype was not a decisive factor for depressive symptoms, possibly due to varied occupational stressors [13]. Nevertheless, the overall picture suggests heightened vulnerability for evening types in the shift work environment.

Chronotype also appears to play a role in stress response and resilience. Evening types are more likely to suffer from social jetlag, which may decrease resilience [14]. While one study suggested that morning types showed higher resilience scores in the morning, eveningness is generally associated with poorer sleep quality, which may mediate the link between chronotype and resilience. Evening types also seem to correlate more strongly with a general vulnerability to stress.

The implications of chronotype for shift work scheduling are becoming increasingly clear. Chronotype seems to explain individual differences in sleep better than age and is considered a key determinant of sleep disturbance in shift nurses [15]. It is important to evaluate chronotype to determine if an individual is suited for shift work. Some research indicates that intelligently designed shift schedules that consider chronotype can reduce circadian disruption and improve sleep. Implementing chronotype-adjusted schedules, such as abolishing the most strenuous shifts for extreme chronotypes (night shifts for early types, morning shifts for late types), has shown positive results, including increased sleep duration and quality on workdays and reduced social jetlag for extreme chronotypes. Recommendations include considering chronotype critically when arranging working times, especially if night shifts are mandatory, and potentially including chronotype information in shift assignment scheduling. However, further wide-scale research is needed to confirm whether matching chronotype to shift patterns consistently benefits mental health [13].

In conclusion, while evening chronotypes may possess a relative advantage in tolerating night shifts compared to their morning counterparts, the available evidence strongly suggests that they remain significantly at risk in a 24/7 world, particularly when engaged in shift work. Their natural biological timing makes them susceptible to the general health consequences of circadian disruption inherent in shift work, including increased risks for metabolic disorders and poorer mental health [3,12]. Furthermore, schedules that require early waking times remain highly disruptive for evening types. The modern environment, characterized by artificial light exposure at night and societal pressures that enforce early starts, exacerbates social jetlag and other health risks for evening types, even among non-shift workers. Chronotype is an often-unrecognized factor contributing to occupational health issues. Moving forward, recognizing and incorporating individual chronotypes into shift work design and occupational health strategies holds promise for mitigating risks and improving the well-being of workers in our round-the-clock society.