Circadian rhythms are endogenous biological oscillations with a periodicity of approximately 24 hours that regulate numerous physiological and behavioural processes. In humans, the central circadian pacemaker is located in the suprachiasmatic nucleus of the hypothalamus, while peripheral clocks exist in metabolically important tissues including the liver, pancreas, adipose tissue, skeletal muscle, and gastrointestinal tract. Coordination between central and peripheral oscillators facilitates the temporal organization of sleep, hormone secretion, glucose metabolism, lipid metabolism, blood pressure, appetite, and energy expenditure.[1,2]

Modern occupational schedules can substantially interfere with this physiological organization. Shift work, particularly fixed night and rotating shift work, requires individuals to remain awake, active, and frequently consume food during the biological night while attempting to sleep during daytime hours. This produces a mismatch between endogenous circadian timing and behavioural schedules and may be accompanied by shortened sleep duration, irregular meal timing, artificial-light exposure, and occupational stress.[2,3]

Experimental evidence supports a direct metabolic consequence of circadian misalignment. Scheer et al. demonstrated that experimentally induced circadian misalignment altered glucose and insulin concentrations, reduced leptin, reversed the normal cortisol rhythm, and increased mean arterial pressure.[1] Subsequent research has strengthened the hypothesis that circadian disruption may influence obesity, glucose intolerance, diabetes, hypertension, and cardiovascular risk.[2,3]

Shift work represents one of the most extensively studied real-world models of chronic circadian disruption. A meta-analysis by Sun et al. demonstrated an association between shift work and obesity, particularly abdominal obesity.[4] More recent evidence has shown an increased incidence of type 2 diabetes among night-shift workers.[5] Abnormal glucose regulation among shift workers may reflect interactions among circadian misalignment, reduced sleep, altered insulin sensitivity, inappropriate meal timing, and lifestyle factors.[5,6]

Healthcare workers constitute a particularly important occupational population. Hospitals operate continuously, necessitating night duties and rotating schedules among doctors, postgraduate residents, nurses, technicians, laboratory personnel, pharmacists, and other employees. In addition to circadian disruption, healthcare workers may encounter prolonged duty hours, psychological stress, unpredictable emergencies, irregular meals, and inadequate opportunities for restorative sleep.

Metabolic syndrome provides a clinically relevant framework through which the consequences of circadian disruption can be investigated because it represents a cluster of central obesity, abnormal glucose regulation, elevated blood pressure, hypertriglyceridaemia, and reduced HDL cholesterol. Individuals with metabolic syndrome have substantially elevated long-term risks of type 2 diabetes and cardiovascular disease.

Evidence also indicates that circadian disruption should not be considered exclusively an occupational phenomenon. Social jetlag, evening chronotype, insufficient sleep, and inappropriate meal timing have been associated with adverse metabolic outcomes.[3,7] These findings suggest that both occupational schedules and their effects on sleep and behavioural timing may contribute to metabolic health.

The present study was therefore designed to assess the relationship between occupational circadian rhythm disruption and metabolic health among healthcare workers employed at a tertiary care teaching centre. Particular attention was given to anthropometric parameters, blood pressure, glucose metabolism, lipid profile, sleep characteristics, and the prevalence of metabolic syndrome.

Aim

To assess the association between circadian rhythm disruption related to occupational shift work and metabolic health among healthcare workers at a tertiary care teaching centre.

Study Design and Setting An observational analytical study was designed to evaluate the relationship between occupational circadian rhythm disruption and metabolic health among healthcare workers employed at a tertiary care teaching centre. The hospital provides continuous 24-hour healthcare services and includes workers exposed to conventional daytime schedules as well as fixed night and rotating shift schedules. Study Population A total of 200 healthcare workers were considered in the illustrative analysis. Participants included healthcare personnel eligible according to the predefined study criteria. They were classified according to their usual occupational schedule into: • Daytime workers: 100 • Shift workers: 100 o Fixed night-shift workers: 35 o Rotating shift workers: 65 Shift work was defined as regular occupational activity outside conventional daytime hours, including night or rotating duties. Eligibility Criteria Adult healthcare workers employed at the selected tertiary care teaching centre, having an established work schedule and willing to provide written informed consent, were eligible. Individuals unable or unwilling to complete study procedures and those with conditions substantially affecting circadian rhythm or metabolic parameters independently of occupational exposure could be excluded according to the approved protocol. Pregnancy and medications substantially influencing glucose or lipid metabolism were also considered during eligibility assessment. Data Collection A structured study proforma was designed to collect demographic, occupational, behavioural, sleep-related, anthropometric, clinical, and biochemical information. Occupational variables included designation, department, duration of employment, number of night duties per month, consecutive night duties, frequency of shift rotation, duration of each shift, and cumulative years of night-shift exposure. Sleep assessment included average sleep duration, sleep timing, difficulty initiating or maintaining sleep, frequent awakenings, daytime sleepiness, and subjective sleep quality. Validated instruments such as the Pittsburgh Sleep Quality Index could be used according to the final approved protocol. Anthropometric Measurements Body weight was measured using a calibrated weighing scale, and height was measured using a standardized stadiometer. Body mass index was calculated as: BMI = weight (kg)/height² (m²). Waist circumference was measured using a non-stretchable measuring tape at a standardized anatomical location. Blood Pressure Participants rested for at least five minutes before blood-pressure assessment. Measurements were obtained in the seated position using an appropriate cuff. At least two measurements could be obtained, with the average used for analysis. Biochemical Investigations Venous blood samples were collected after approximately 8–12 hours of overnight fasting. Biochemical assessment included: • Fasting plasma glucose • HbA1c • Total cholesterol • Triglycerides • HDL cholesterol • LDL cholesterol For shift workers, blood-sampling times were standardized as far as practicable to reduce acute variation attributable to recent meals and work schedules. Assessment of Metabolic Syndrome Metabolic syndrome was evaluated using predefined internationally recognized harmonized criteria. The components included central obesity, elevated triglycerides, reduced HDL cholesterol, elevated blood pressure, and elevated fasting glucose or treatment for the corresponding abnormality.[16] Ethnicity-appropriate waist-circumference thresholds were intended to be applied. Statistical Analysis Continuous variables were summarized as mean±standard deviation or median and interquartile range as appropriate. Categorical variables were expressed as frequencies and percentages. Independent-samples t-tests or appropriate non-parametric tests were planned for continuous variables, while chi-square or Fisher's exact tests were used for categorical variables. Correlation analysis evaluated associations between duration of shift exposure and continuous metabolic parameters. Multivariable logistic regression was planned to determine whether shift work was independently associated with metabolic syndrome after accounting for potential confounders including age, sex, BMI, physical activity, smoking, dietary pattern, and sleep duration. Statistical significance was set at p<0.05. Ethical Considerations The study protocol requires Institutional Ethics Committee approval before recruitment. Written informed consent is to be obtained from all participants, and confidentiality is to be maintained using coded study information.

Important publication note: All numerical findings below are derived from the protocol's explicitly labelled illustrative dataset and must be replaced or verified against the actual participant dataset before journal submission.

A total of 200 healthcare workers were represented, comprising 100 daytime and 100 shift workers. Among shift workers, 35% had fixed night schedules and 65% rotating schedules. Mean duration of shift-work exposure was 5.6±3.2 years.

Table 1. Comparison of anthropometric and blood-pressure parameters

Shift workers demonstrated higher BMI and waist circumference than daytime workers. Increased waist circumference occurred in 54% compared with 31%, while elevated blood pressure/hypertension was reported in 34% compared with 18%.

Table 2. Comparison of biochemical parameters

The illustrative biochemical profile was consistently less favourable among shift workers. Fasting glucose, HbA1c, total cholesterol, triglycerides, and LDL cholesterol were higher, whereas HDL cholesterol was lower.

Table 3. Metabolic abnormalities and metabolic syndrome

*Illustrative p-value as provided in the source protocol.

Metabolic syndrome occurred in 38% of shift workers compared with 18% of daytime workers in the illustrative analysis. All five individual metabolic abnormalities were also more frequent among shift workers.

Table 4. Illustrative multivariable logistic regression for predictors of metabolic syndrome

In the illustrative adjusted analysis, shift workers had approximately 2.4-fold higher odds of metabolic syndrome. BMI, age, and short sleep duration also demonstrated independent associations.

The present study examined the relationship between occupational circadian rhythm disruption and metabolic health among healthcare workers. The illustrative analysis showed a consistent pattern in which shift workers had higher BMI, greater waist circumference, higher blood pressure, less favourable glycaemic and lipid profiles, and a greater prevalence of metabolic syndrome than daytime workers. One of the prominent findings was the difference in adiposity. Shift workers had a mean BMI of 26.1 kg/m² compared with 23.8 kg/m² among daytime workers. Increased waist circumference was observed in 54% of shift workers compared with 31% of daytime workers. These findings are consistent with the meta-analysis by Sun et al., which demonstrated an association between shift work and obesity, particularly abdominal obesity.[4] Several mechanisms could explain this relationship. Night work alters the timing of sleep and food intake and may increase opportunities for consumption of energy-dense foods. Sleep restriction can additionally alter appetite regulation, while circadian misalignment may modify energy expenditure and substrate metabolism.[2,3] The combination may facilitate progressive weight gain and visceral adiposity. Blood pressure was also higher among shift workers. Mean systolic and diastolic blood pressure values were increased, and elevated blood pressure/hypertension was nearly twice as prevalent among shift workers. Circadian disruption can affect sympathetic activity, cortisol secretion, sleep-related cardiovascular recovery, and the physiological nocturnal decline in blood pressure. Healthcare-related occupational stress may further contribute to this relationship. Glycaemic abnormalities represented another important finding. Shift workers demonstrated higher fasting glucose and HbA1c. This is biologically plausible because glucose tolerance and insulin sensitivity exhibit circadian variation and tend to deteriorate during the biological night. Consumption of meals during night duty may therefore impose a metabolic load at a physiologically less favourable time.[1,2] The results are consistent with evidence associating shift work with type 2 diabetes. Xie et al. reported increased type 2 diabetes incidence among night-shift workers in a cohort-based meta-analysis.[5] Wang et al. also reported an association between shift work and increased diabetes risk and altered metabolic biomarkers.[6] The lipid profile demonstrated a similarly adverse pattern. Shift workers had higher triglycerides, total cholesterol, and LDL cholesterol and lower HDL cholesterol. Circadian regulation of hepatic lipid metabolism, together with differences in diet, physical activity, body composition, and insulin sensitivity, may contribute to these abnormalities. Of particular clinical importance was the clustering of metabolic abnormalities. Central obesity, elevated blood pressure, hypertriglyceridaemia, reduced HDL cholesterol, and elevated fasting glucose were all more frequent among shift workers. Consequently, metabolic syndrome was present in 38% of shift workers compared with 18% of daytime workers in the illustrative dataset. The source protocol also indicates that metabolic syndrome occurred more frequently among rotating than fixed night workers—43.1% versus 28.6%, respectively. Repeated transitions between daytime and nighttime activity may prevent stable circadian adaptation and generate recurrent misalignment. Nevertheless, such findings require cautious interpretation because shift type interacts with age, duration of employment, sleep, diet, physical activity, and other potential confounders. A possible exposure-response relationship was also apparent. The protocol's illustrative results showed increasing metabolic-syndrome prevalence with increasing duration of shift work. Furthermore, duration of shift work correlated positively with BMI, waist circumference, fasting glucose, triglycerides, and systolic blood pressure. These findings support the possibility that cumulative circadian disruption contributes to progressive metabolic risk. Sleep may represent an important mediator. The illustrative data demonstrated shorter mean sleep duration among shift workers, with substantially more workers reporting less than six hours of sleep. Participants sleeping fewer than six hours also showed a higher prevalence of metabolic syndrome than those obtaining at least seven hours. The multivariable model further supported this interconnected relationship. Shift work retained an illustrative adjusted odds ratio of 2.41 for metabolic syndrome after adjustment for selected confounding variables. Short sleep duration also remained associated with metabolic syndrome. These findings suggest that occupational schedule and insufficient sleep could potentially make partially independent contributions to metabolic risk.

Important publication note: All numerical findings below are derived from the protocol's explicitly labelled illustrative dataset and must be replaced or verified against the actual participant dataset before journal submission.

A total of 200 healthcare workers were represented, comprising 100 daytime and 100 shift workers. Among shift workers, 35% had fixed night schedules and 65% rotating schedules. Mean duration of shift-work exposure was 5.6±3.2 years.

Table 1. Comparison of anthropometric and blood-pressure parameters

Shift workers demonstrated higher BMI and waist circumference than daytime workers. Increased waist circumference occurred in 54% compared with 31%, while elevated blood pressure/hypertension was reported in 34% compared with 18%.

Table 2. Comparison of biochemical parameters

The illustrative biochemical profile was consistently less favourable among shift workers. Fasting glucose, HbA1c, total cholesterol, triglycerides, and LDL cholesterol were higher, whereas HDL cholesterol was lower.

Table 3. Metabolic abnormalities and metabolic syndrome

*Illustrative p-value as provided in the source protocol.

Metabolic syndrome occurred in 38% of shift workers compared with 18% of daytime workers in the illustrative analysis. All five individual metabolic abnormalities were also more frequent among shift workers.

Table 4. Illustrative multivariable logistic regression for predictors of metabolic syndrome

In the illustrative adjusted analysis, shift workers had approximately 2.4-fold higher odds of metabolic syndrome. BMI, age, and short sleep duration also demonstrated independent associations.

The present study examined the relationship between occupational circadian rhythm disruption and metabolic health among healthcare workers. The illustrative analysis showed a consistent pattern in which shift workers had higher BMI, greater waist circumference, higher blood pressure, less favourable glycaemic and lipid profiles, and a greater prevalence of metabolic syndrome than daytime workers. One of the prominent findings was the difference in adiposity. Shift workers had a mean BMI of 26.1 kg/m² compared with 23.8 kg/m² among daytime workers. Increased waist circumference was observed in 54% of shift workers compared with 31% of daytime workers. These findings are consistent with the meta-analysis by Sun et al., which demonstrated an association between shift work and obesity, particularly abdominal obesity.[4] Several mechanisms could explain this relationship. Night work alters the timing of sleep and food intake and may increase opportunities for consumption of energy-dense foods. Sleep restriction can additionally alter appetite regulation, while circadian misalignment may modify energy expenditure and substrate metabolism.[2,3] The combination may facilitate progressive weight gain and visceral adiposity. Blood pressure was also higher among shift workers. Mean systolic and diastolic blood pressure values were increased, and elevated blood pressure/hypertension was nearly twice as prevalent among shift workers. Circadian disruption can affect sympathetic activity, cortisol secretion, sleep-related cardiovascular recovery, and the physiological nocturnal decline in blood pressure. Healthcare-related occupational stress may further contribute to this relationship. Glycaemic abnormalities represented another important finding. Shift workers demonstrated higher fasting glucose and HbA1c. This is biologically plausible because glucose tolerance and insulin sensitivity exhibit circadian variation and tend to deteriorate during the biological night. Consumption of meals during night duty may therefore impose a metabolic load at a physiologically less favourable time.[1,2] The results are consistent with evidence associating shift work with type 2 diabetes. Xie et al. reported increased type 2 diabetes incidence among night-shift workers in a cohort-based meta-analysis.[5] Wang et al. also reported an association between shift work and increased diabetes risk and altered metabolic biomarkers.[6] The lipid profile demonstrated a similarly adverse pattern. Shift workers had higher triglycerides, total cholesterol, and LDL cholesterol and lower HDL cholesterol. Circadian regulation of hepatic lipid metabolism, together with differences in diet, physical activity, body composition, and insulin sensitivity, may contribute to these abnormalities. Of particular clinical importance was the clustering of metabolic abnormalities. Central obesity, elevated blood pressure, hypertriglyceridaemia, reduced HDL cholesterol, and elevated fasting glucose were all more frequent among shift workers. Consequently, metabolic syndrome was present in 38% of shift workers compared with 18% of daytime workers in the illustrative dataset. The source protocol also indicates that metabolic syndrome occurred more frequently among rotating than fixed night workers—43.1% versus 28.6%, respectively. Repeated transitions between daytime and nighttime activity may prevent stable circadian adaptation and generate recurrent misalignment. Nevertheless, such findings require cautious interpretation because shift type interacts with age, duration of employment, sleep, diet, physical activity, and other potential confounders. A possible exposure-response relationship was also apparent. The protocol's illustrative results showed increasing metabolic-syndrome prevalence with increasing duration of shift work. Furthermore, duration of shift work correlated positively with BMI, waist circumference, fasting glucose, triglycerides, and systolic blood pressure. These findings support the possibility that cumulative circadian disruption contributes to progressive metabolic risk. Sleep may represent an important mediator. The illustrative data demonstrated shorter mean sleep duration among shift workers, with substantially more workers reporting less than six hours of sleep. Participants sleeping fewer than six hours also showed a higher prevalence of metabolic syndrome than those obtaining at least seven hours. The multivariable model further supported this interconnected relationship. Shift work retained an illustrative adjusted odds ratio of 2.41 for metabolic syndrome after adjustment for selected confounding variables. Short sleep duration also remained associated with metabolic syndrome. These findings suggest that occupational schedule and insufficient sleep could potentially make partially independent contributions to metabolic risk.

The illustrative findings suggest that occupational circadian rhythm disruption associated with night and rotating shift work may be linked to adverse metabolic health among healthcare workers. Shift workers demonstrated higher adiposity, blood pressure, fasting glucose, HbA1c, triglycerides and LDL cholesterol, lower HDL cholesterol, and a greater prevalence of metabolic syndrome than daytime workers.

Longer shift-work exposure and insufficient sleep also appeared to be associated with greater metabolic risk. These observations support the importance of circadian and occupational health in healthcare institutions.

Before publication, however, all illustrative numerical results must be replaced or validated against the actual study dataset. Prospective multicentre studies incorporating objective circadian measurements are warranted to clarify causality and determine whether modification of shift schedules, sleep timing, and meal timing can reduce cardiometabolic risk.