Unraveling the complex relationship between night shift work and diabetes: exploring mechanisms and potential interventions

Circadian rhythms refer to the recurring 24-h patterns that occur in all forms of life, regulating a diverse range of biological activities (60). The main internal clock in mammals is mostly found in the suprachiasmatic nucleus (SCN) located in the front part of the hypothalamus. Moreover, there are peripheral clocks present in multiple areas of the brain, as well as nearly all peripheral tissues and organs (61). The biological timekeeper, consisting of fundamental timekeeping genes such as clock, bmal, and per (1, 2, and 3), cry (1 and 2), rev-erba, and ROR, functions by maintaining a constant cycle of transcription and translation through a mechanism of self-regulated feedback that spans ~24 h. Any disruption in these fundamental genes responsible for regulating the body's internal clock can increase a person's vulnerability to developing T2DM, gaining excessive weight, and experiencing metabolic syndrome (62, 63). The hormone cortisol exemplifies the importance of circadian rhythmicity in metabolic regulation. Cortisol normally follows a distinct pattern, peaking upon waking and reaching its lowest point at sleep onset. This rhythm plays a crucial role in glucose homeostasis throughout the day. When this pattern is disrupted, as in night shift work, metabolic dysregulation often follows. Loss of synchrony between circadian clocks and hormonal rhythms directly contributes to metabolic disorders. Evidence from shift workers demonstrates that this desynchronization is associated with obesity, depression, and T2DM (64). The implications extend beyond simply feeling tired—circadian misalignment fundamentally alters how the body processes nutrients, particularly glucose. The SCN transmits synchronized time-of-day data to the entire brain through direct or indirect neural pathways, such as the parasympathetic and sympathetic nervous systems. It can also influence the release of factors such as insulin and melatonin (65). It is significant to mention that sympathetic nerve activity triggers the production of glucose, whereas parasympathetic nerve activity promotes the formation of hepatic glycogen in the liver. Individuals with prediabetes display heightened sympathetic activity before encountering insulin resistance, which differentiates them from their healthy counterparts (66).

Humans typically differ from most other mammals in terms of their sleep habits. Unlike other animals, humans tend to have uninterrupted sleep for a stretch of 7–9 h, leading to a longer period of fasting overnight (67). The quality of sleep significantly affects the functioning of pancreatic β-cells and the body's ability to process insulin (68). Interestingly, even though there is a prolonged period of not eating during overnight sleep, blood sugar levels stay consistent or experience only slight drops. When people are both alert and abstaining from eating while lying down without moving, their glucose levels typically decrease by an average of 10 to 20 mg/dL within a 12-h period (69–71). As previously explained, glucose serves as the main source of energy and is broken down by practically all recognized living beings to sustain their survival (72). Due to the fact that an organism's energy requirements change according to the time of day, the fluctuations in glucose metabolism during the day can be attributed, at least in part, to the changing utilization of glucose on a daily basis (73). The levels of glucose in the blood are influenced by the coordinated regulation of how much glucose is consumed through food and how much is produced by the liver, as well as how much is used by the muscles and adipose tissues. Many researchers have documented a consistent cycle in the levels of glucose found in the bloodstream over the course of a day. The first suggestion of the involvement of the SCN in regulating glucose levels was discovered through studies showing that damaging the bilateral SCN significantly disrupted the regular patterns of both plasma glucose and insulin. These lesions also eliminated the distinct day-to-night response to 2-deoxy-glucose, an inhibitor of glucose utilization, as noted in the study by Nagai et al. (74).

The baseline glucose levels in mild fasting conditions, such as before meals, show a diurnal pattern in healthy animals and human participants, influenced by regular light and dark cycles. This rhythm reaches its peak upon waking and hits a trough during sleep (75). It is significant to note that this daily cycle is not exclusively caused by a person's eating habits, as it remains present even when fasting takes place at varying times (76). The use of isotope tracers has revealed a concordant daily pattern in the production of natural glucose within the bodies of individuals who are in good health (77). This discovery suggests that the daily variation in glucose levels is mainly connected to the endogenous glucose production. The liver is essential to the process of EGP, as it either breaks down glycogen or creates glucose through the process of gluconeogenesis. Corresponding to this, the substance of liver glycogen demonstrates a daily pattern that contradicts the daily baseline levels of glucose observed in humans (78). The natural daily rhythm of normal glucose levels is disrupted in animals that have damage to the SCN. The removal of SCN results in a heightened level of c-Fos expression in ARC neurons caused by 2-deoxy-glucose, which further exacerbates hyperglycemia after waking up. The implication is that the SCN-ARC projection could potentially have a significant impact on maintaining the daily glucose cycle by aiding in the counteractive response to hypoglycemia (74, 79). Unlike people who are in good health, individuals who have prediabetes experience an alteration in the timing of their fasting blood sugar fluctuations, as their highest blood sugar level occurs later in the day. After analyzing hypothalamic tissue taken from deceased individuals with T2DM, it was found that there was a decrease in the amount of neurons in the SCN region compared to those without the condition. The act of observing implies that there is a chance that people with T2DM may experience disruptions in their SCN (80).

The daily pattern of changes in glucose levels after eating is significantly different from the initial levels of glucose before eating. In individuals with good health, consuming the same meal leads to a larger rise in glucose levels at dinner than at breakfast (81). According to research conducted on humans using the oral glucose minimal model or hyperinsulinemia-euglycemic clamp, it has been observed that insulin sensitivity is at its peak in the morning and gradually declines throughout the day, reaching its lowest level during sleep. The significant changes in EGP inhibition via insulin demonstrate notable fluctuations throughout the day (82). The SCN plays a vital role in the fluctuations of glycemic responses to meals based on the time of day. When the SCN is damaged, the diurnal pattern in glucose tolerance is abolished. Moreover, it is essential for the correct functioning of clock genes in the SCN in order to maintain the daily fluctuations in glucose tolerance and hepatic insulin sensitivity (83, 84).

It may seem contradictory to have both elevated baseline glucose levels and increased insulin sensitivity upon awakening, but this can be explained from an evolutionary perspective. When the body enters a state of sleep, the need for EGP to ensure the blood sugar levels remain steady increases. The need for energy is highest right after waking up and right before a meal, since the body requires glucose to function effectively for tasks such as thinking and moving while searching for food on an empty stomach (85, 86). Insulin entering the body after a meal unlocks this capability and finalizes the change from elevated pre-meal glucose production to reduced post-meal glucose production. Therefore, the SCN clock is crucially essential in regulating the predictive management of liver response to insulin, working alongside insulin signaling to coordinate the daily cycle of glucose processing in typical physiological circumstances (87). When a person is in a normal physical condition, both the initial amount of endogenous glucose production and its responsiveness to insulin-induced decrease reach their highest levels upon awakening. It should be emphasized that while the autonomous nervous system (ANS) plays a key role in regulating glucose rhythms as discussed previously, the SCN also has the ability to impact the daily liver glucose rhythm through the release of certain factors (88). As such, the regulation of blood sugar levels is influenced by both the SCN as well as the peripheral clocks found in different tissues. Recent studies indicate that disturbances in the body's natural patterns of biological processes can have an effect on the way metabolic pathways function. The internal system for keeping time is intricately connected to the circadian control of glucose metabolism and the functioning of insulin. In this light, changes in the daily pattern of glucose tolerance serve as an initial sign of T2DM. In contrast to healthy individuals, those who have prediabetes show improved management of glycemic levels when consuming a bolus dose of glucose or a meal in the evening rather than in the morning (89). The study of disease patterns shows that the disruption of the body's internal clock can be caused by various factors, such as inconsistent eating habits, minimal exposure to daylight, higher exposure to light at night due to shift work, lack of sleep, having a late sleep schedule, social jet lag, and other elements. These factors are linked to an increased risk of developing T2DM (90). The internal biological clocks within pancreatic β-cells are responsible for controlling the timing of gene transcription related to important processes such as glucose metabolism, protection against oxidative damage, and insulin release. Figure 1 strengthens the correlation between circadian rhythms and T2DM (63).

The regulation of carbohydrate, lipid, and protein metabolism through circadian rhythms is dependent on a collective control by oscillators (91). The circadian rhythm plays a crucial role in controlling the expression and activities of crucial metabolic components, such as receptors, transporters, and enzymes. Disruptions in peripheral clocks located in a range of organs (such as the liver, muscles, pancreas, adipose tissue, intestines, kidneys, etc.) contribute to altering metabolic traits (92). The levels of glucose tolerance in humans vary on a daily basis. The occurrence of this phenomenon is a direct consequence of the everyday fluctuations in peripheral insulin sensitivity, which are caused by essential internal cellular mechanisms that regulate the intake of glucose. The liver releases glucose while the body is at rest, but during periods of physical activity, other organs absorb glucose (93). Individuals who are overweight or advanced in age may experience patterns that are diminished, postponed, or nonexistent. The dawn phenomenon, which describes the rise in blood sugar levels in the morning, can be attributed to changes in the body's response to insulin (94). Disrupting the function of clock genes through changes in their genetic makeup leads to a decrease in the production of TBC1D1, GLUT4, and hexokinase, resulting in a deficiency in the ability to use glucose when stimulated by insulin. Metabolic detectors, including Sirt1, AMPK, PGC-1a, NAD, and FAD, have the function of transmitting the cell's energy level to the primary circadian rhythm (95). The absence of a circadian rhythm in β-cells has been found to decrease the conversion of substrates, the production of ATP, and the transportation of vesicles, ultimately resulting in diminished insulin secretion (96). The balance between NAD and NADH is vital in dictating the interaction of the NPAS2-CLOCK partnership with specific genes in the body. The circadian rhythm of metabolism is controlled by transcription factors, such as DBP, Rev-Reba, PPARg, HLF, and TEF, which play a crucial role in regulating different metabolic pathways (97). If the circadian rhythms are disturbed, it can cause an improper regulation of mitochondrial function, resulting in a higher production of reactive oxygen species (ROS) (98). ROR proteins and PGC-1a play a crucial role in controlling the diurnal rhythms of lipid and glucose metabolism (99). Both the MTP found in the intestines and the MTP found in the liver show cyclical patterns of activity, peaking at the same time as the levels of lipids in the blood. In addition, the activity of clock genes in the intestines controls the cyclical production of MTP, apolipoprotein A IV, and nocturnin, which are all essential components in the process of absorbing lipids (100). REV-REBa's circadian function plays a pivotal role in regulating the periodic production of enzymes responsible for synthesizing lipids (99).

The naturally occurring patterns of physiological processes, such as the production of certain enzymes involved in the breakdown of fats, namely HMG CoA reductase, hormone-sensitive lipase, carnitine palmitoyltransferase 1, and medium-chain acyl-CoA dehydrogenase, are known as circadian rhythms. Genetic mutations in the clock gene of mice lead to alterations in the periodic manifestation of genes that control the production of triglycerides (TGs) and the breakdown of fats. The Clock gene plays a significant role in reducing the activity of microsomal triglyceride transfer protein (MTP) by specifically attaching to the Hepatocyte Nuclear Factor4 located at the MTP promoter site. This process is crucial for maintaining daily variations in plasma triglyceride levels, achieved through the regulation of adipogenesis by BMAL1 and the control of important factors involved in both adipogenesis and lipogenesis (101). The interference with genes regulated by the internal clock (CCGs) that are located after the main clock mechanism has an impact on the processing of lipids. Mice that were put on a low-protein diet encountered disruptions in the regular fluctuations of plasma glucose, triglycerides, and insulin levels. Restricting protein intake can cause alterations in the peripheral clock, highlighting the importance of appropriate nutrition in regulating the biological clock. Moreover, inadequate protein consumption throughout pregnancy has been discovered to impede the body's daily rhythm system and affect several aspects associated with metabolic syndrome. Moreover, peripheral oscillators have experienced interruptions as a result of neuronal alterations within the SCN (102).

As mentioned earlier, the circadian system has developed to produce ~24-h patterns in both behavior and bodily processes. This ability allows the organism to anticipate and accommodate the recurring changes in its surroundings, such as the cycle of light and darkness resulting from the Earth's rotation. The internal biological rhythms found in mammals are a product of a complex system of oscillators. This includes the primary circadian pacemaker located in the hypothalamic SCN and smaller clocks found in various organs, tissues, and cells throughout the body. The primary means of synchronization for the SCN is through light input, which is achieved through direct photic signals that originate in the retina and are then transmitted to the SCN via the retinohypothalamic tract. The primary function of the SCN is to align and coordinate the peripheral clocks by utilizing signals from neurons, behaviors, body temperature, and hormones. The SCN is responsible for producing melatonin, which is recognized as one of the most commonly recognized hormonal signals (103). The pineal gland in the brain of mammals is responsible for the production and release of melatonin at night, following a regular cycle known as the circadian rhythm. It acts as a middleman for regulating internal biological cycles and has an influence on various bodily processes. Melatonin displays a multitude of beneficial properties including anti-oxidative, anti-inflammatory, and anti-aging effects. Additionally, it plays a crucial role in treating a variety of sleep disorders (104, 105). The main function of Melatonin on a physiological level is to convey important details regarding the length and timing of the night to the entire body (73). The synthesis of melatonin in mammals is governed by an intricate sympathetic pathway that stems from the SCN to the pineal gland. The primary determinants of the amount of melatonin found in the bloodstream are the current phase of the circadian rhythm and the amount of light exposure. For people who follow a schedule during the day, there is a rise in their melatonin levels a couple of hours before their usual bedtime. These levels stay high throughout the night, but then decrease in the early hours after they typically wake up. For the rest of the day, the levels remain very low. When exposed to light at night, there is a swift and proportional decrease in melatonin levels, whereas being in darkness during the day does not trigger the production of melatonin. The regulation of both the circadian rhythm and the suppression of melatonin by light are controlled by the SCN, which receives visual signals from specialized retinal ganglion cells that are sensitive to light through the retinohypothalamic tract (106, 107).

Famous for its function as a coordinating factor or timekeeper, melatonin is actively engaged in coordinating the cyclical patterns in different physiological functions within the body. The glucose tolerance of individuals in good health follows a consistent daily trend, with a gradual decrease in tolerance as the day goes on (67). The regular pattern continues to exist even when the impact of external and personal factors is eliminated, indicating that it is regulated by one's internal body clock (108). Melatonin, known for its elevated levels during the night and its ability to lower glucose tolerance, may be a contributing factor to the decline in glucose tolerance during nighttime in human beings (109). Furthermore, numerous well-established processes governed by regulatory pathways, such as the autonomic nervous system, changing hormone levels (such as glucocorticoids), and self-regulating peripheral clocks with the ability to affect organ function (such as insulin secretion from pancreatic islets and insulin sensitivity of adipocytes), play a role in this phenomenon (110, 111).

Over the past few years, there has been a significant amount of research done on the effects of melatonin on insulin release and the regulation of glucose levels in the body. Melatonin carries out its actions through two different forms of receptor proteins located on the membrane, which are called MT1 (also known as Mel1a and encoded by MTNR1A) and MT2 (also known as Mel1b and encoded by MTNR1B). These specific receptors fall into the category of G-protein coupled receptors and have the ability to convey the effects and effects of melatonin through their interaction with Gi proteins that are sensitive to pertussis toxin. This communication leads to the blocking of adenylate cyclase (AC), which eventually causes a decline in cellular cAMP concentrations. As a result, these occurrences have an impact on the subsequent objectives (112). Moreover, it is crucial to acknowledge the presence of a different binding site that has a strong attraction to melatonin, specifically the MT3 subtype (Mel1C). This particular variation has been effectively reproduced from non-mammalian creatures such as zebrafish, Xenopus, and chicken. Despite extensive research, this subtype has yet to be detected in mammals (113). In the world of mammalian species, the distinct equivalent of MT3 can be found in the form of GPR50, a receptor that has yet to be fully understood or classified. It should be noted that despite being mentioned, GPR50 does not possess the ability to bind to melatonin, and its role in human biology is still unknown (110). Research revealed that when melatonin was administered through an intracerebroventricular injection, it triggered the activation of hypothalamic Akt and inhibited hepatic gluconeogenesis. The discovery suggests that melatonin is involved in promoting communication between the hypothalamus and the liver. This subsequently implied a possible connection between the decreased amounts of melatonin found in those with T2DM and disruptions in the body's circadian metabolic functions (114). On the other hand, in contrast to the widely accepted idea that melatonin plays a key role in regulating glucose metabolism, there is a decrease in melatonin production when there is high blood sugar. This disability is linked to a potential initial decline in the level of β-adrenergic receptors, which play a vital role in kickstarting the process of producing melatonin. It is widely believed that this decrease will cause even more disruption to the control of glucose levels and intensify the progression of T2DM (115).

Since insulin plays a critical role in regulating metabolism, it is imperative to focus on how melatonin affects the secretion of insulin. Melatonin decreases the secretion of insulin (116). Numerous studies have affirmed that melatonin's role in regulating insulin release is achieved by engaging in communication with both the MT1 and MT2 receptors. By utilizing the melatonin receptors and the accompanying signaling cascade facilitated by the Gi-proteins, melatonin has the ability to suppress the AC/cAMP system (in the instances of MT1 and MT2) and the GC/cGMP system (with a focus on MT2), effectively decreasing the levels of insulin released. On the other hand, if melatonin receptors bind with Gq proteins, this triggers phospholipase C to initiate the production of insulin through the IP3-signaling pathway. However, it should be emphasized that melatonin predominantly has a detrimental effect on the release of insulin (117).

Melatonin's well-established ability to hinder insulin is marked by a contradictory rhythmic fluctuation between these two hormones, a phenomenon that is also apparent in cases of T2DM (118). In the initial phases of T2DM, there is an increase in insulin secretion but a decrease in melatonin levels. Conversely, in type 1 diabetes, there is a reverse connection between these two factors (119, 120). The link between T2DM and this symbiotic connection is primarily attributed to catecholamines, specifically NE, according to current theories. Catecholamines can stimulate the production and release of melatonin through receptors like adrenoceptor β1-cAMP or α1-IP3 cascade, while at the same time blocking insulin secretion through α2 receptors. Additionally, α2 receptors have the ability to decrease the release of norepinephrine by acting on nerve terminal autoreceptors. These mechanisms may provide an explanation for the diminished plasma catecholamines, reduced melatonin, and elevated insulin levels observed in T2DM, as elucidated in studies by Frese et al. (121) and Peschke et al. (122). It is believed that melatonin serves as a protective measure against the strain on β-cells caused by T2DM by inhibiting insulin secretion, as the depletion of these cells is linked to the development of the disease. As a result, this process provides a safeguard against the progress of T2DM. Therefore, the decrease in melatonin levels and the rise in incidence of insulin resistance and T2DM among aging individuals can be acknowledged as a result of melatonin's defensive effects on β-cells and their performance (123). Within the framework of type 1 diabetes, the increased quantities of melatonin serve as a protective measure utilized by the body to counter the strain caused by diabetes, thereby reducing the harm caused to β-cells due to oxidative stress (124). As a whole, melatonin has the ability to improve the functioning of β-cells and hinder the development of T2DM (refer to Figure 2 for a visual depiction of this).

The results of studies performed in controlled laboratory environments with individuals who are in good health have confirmed a correlation between decreasing the amount of sleep and a decrease in the body's ability to respond to insulin (125). Research has shown a marked decline in the brain's consumption of glucose when deprived of sleep for extended periods (126). Additionally, restricting the amount of sleep resulted in a decrease in the ability of subcutaneous fat cells to respond to insulin in healthy individuals (127). Multiple intermediate processes could be involved in this correlation (Figure 3). Sleep restriction is associated with an increase in activity of the sympathetic nervous system. The sympathetic nervous system has a profound impact on a variety of bodily processes, including the secretion of insulin and glucagon, the development of muscle insulin resistance, and the function of adipocytes (128). The initiation of the hypothalamic-pituitary-adrenal (HPA) axis may also contribute to this occurrence. Research has shown a strong correlation between lack of sleep and increased levels of salivary and serum cortisol, as well as the absence of the usual decrease in serum cortisol during the evening (129). Several research projects examining the effects of limited sleep have shown that cortisol levels are significantly higher during the later parts of the day, and these rises may play a role in the development of insulin resistance. However, it is important to acknowledge that while the reversal of the normal cortisol rhythm has been proven to cause insulin resistance, there was not always a direct correlation between changes in cortisol levels and changes in insulin sensitivity after periods of sleep deprivation (130). Extended GH release during sleep deprivation may add to insulin resistance in the morning (131). Furthermore, sleep restriction consistently leads to an increase in inflammatory markers, with notable variations in the levels of IL-1β, IL-6, IL-17, TNF-α, hsCRP, as well as a rise in leukocyte and monocyte counts. Insulin resistance has been linked with these markers of inflammation (132).

Furthermore, an increase in sympathetic activity causes an increase in the breakdown of fats, leading to an increase in levels of free fatty acids in the bloodstream. This can ultimately lead to the buildup of fat in the liver and muscles, leading to the development of insulin resistance. The concept of dysfunctional fat cells has gained recognition as a crucial connection between inadequate sleep and negative metabolic effects. The HPA axis activation and heightened sympathetic activity are both believed to contribute to the development of a condition known as “adipocyte insulin resistance” (133). Decreased insulin signaling in adipocytes could potentially trigger the breakdown of fats, leading to the release of NEFA, which could then worsen insulin resistance. Elaborate and continuous growth hormone production during the night and elevated early-morning levels of noradrenaline may play a role in this mechanism, further supported by their close correlation with the increase in nighttime NEFA levels. As previously mentioned, insufficient sleep can have a significant impact on the hormones responsible for regulating appetite, food consumption, and energy usage. This can ultimately lead to indirect effects on glucose metabolism and increase the likelihood of developing T2DM by promoting weight gain and ultimately causing the body to become resistant to insulin (131).

Experimental studies have isolated the specific effects of circadian misalignment on glucose metabolism. Research has demonstrated that both the endogenous circadian system and circadian misalignment independently affect glucose tolerance in shift workers. Postprandial glucose responses were 6.5% higher at 8:00 p.m. than at 8:00 a.m., representing a circadian phase effect independent of behavioral factors. Furthermore, circadian misalignment itself increased postprandial glucose by an additional 5.6%, independent of both behavioral and circadian phase effects (134). These glucose variations appear to result from different insulin mechanisms. In controlled studies, circadian misalignment increased markers of insulin resistance and inflammation independently of sleep loss. Particularly striking was the observation that in male participants exposed to circadian misalignment, both the reduction in insulin sensitivity and the increase in inflammation doubled compared to those maintaining regular sleep schedules (135). This demonstrates that misalignment itself, beyond sleep deprivation, directly impacts metabolic health.

Night shift work triggers multiple pathophysiological mechanisms that collectively increase T2DM risk. Melatonin, the primary marker of the circadian system, has multiple biological actions relevant to cardiometabolic health, including modulation of oxidative stress, inflammation, and vascular function through its receptors (136). Disruption of melatonin signaling during night shifts likely contributes to metabolic dysregulation. Gene expression changes represent another important mechanism. NSW has been shown to modify gene expression and functional readouts in different tissues and organs, which appear to translate into persistent cardiometabolic and endocrine alterations (137). These molecular changes help explain how chronic exposure to night shift work can lead to lasting metabolic consequences even during periods away from work. Night shift work often triggers behavioral changes that compound circadian disruption. Mistimed feeding—eating during the biological night when the digestive system is not optimally prepared to process nutrients—frequently accompanies night shift work (137). This combination of circadian misalignment and inappropriate meal timing synergistically increases metabolic risk.

Sleep disturbances represent another critical pathway. Night shift workers commonly experience reduced sleep quality and quantity, which independently contribute to insulin resistance and glucose dysregulation. Total sleep time and sleep efficiency are frequently compromised in shift workers, creating a vicious cycle of circadian disruption, poor sleep, and metabolic dysfunction (138).

Other lifestyle factors may interact with shift work to further increase T2DM risk. For example, night shift nurses who engage in binge drinking showed evidence of circadian misalignment and increased health risks (139). These behavioral patterns suggest that lifestyle interventions should be an important component of T2DM prevention strategies for shift workers. Light therapy has emerged as a promising intervention for mitigating the negative effects of shift work. Studies show that light therapy significantly improves total sleep time and sleep efficiency in shift workers compared to control groups. Specific light parameters appear important—medium illuminance (900–6,000 lux) for longer durations (≥ 1 h) during night shifts was most effective for extending total sleep time, while higher illuminance and increasing dose of light therapy more beneficially impacted sleep efficiency (138). Personalized approaches to light therapy show particular promise. A randomized controlled trial demonstrated that light therapy personalized to an individual's melatonin rhythms produced greater reductions in circadian misalignment compared to standardized approaches. Participants receiving personalized light therapy showed decreased sleepiness and improved sleep quality, suggesting this precision medicine approach could help mitigate shift work disorder symptoms and potentially reduce associated metabolic risks (140).

More sophisticated circadian-informed lighting strategies are also being developed. One study demonstrated that a circadian-informed lighting intervention markedly accelerated circadian adjustment to night shift schedules compared to standard lighting. By administering bright, blue-enriched light and dim, blue-depleted light at specific times calculated to facilitate rapid circadian adaptation, researchers achieved faster adjustment to night shift schedules (141). The heightened T2DM risk in night shift workers is fundamentally linked to circadian disruption, independent of sleep loss, leading to impaired glucose metabolism, insulin sensitivity, and altered hormonal rhythms. This is further exacerbated by suppressed melatonin, adverse gene expression changes, and detrimental behaviors like mistimed eating and sleep deprivation. Moving forward, research should focus on identifying predictive biomarkers for individual susceptibility, optimizing personalized light therapy strategies, and developing comprehensive behavioral and nutritional interventions specifically tailored for shift workers, to ultimately mitigate this health burden.