Caffeine consumption in anaesthesiology residents and its association with depression, burnout, sleep quality and cognition

Authors

Abstract

AimAnaesthesiology residents are particularly vulnerable to psychiatric morbidity because of demanding on-call schedules, chronic sleep loss and high occupational stress. The aim of this study was to determine the daily caffeine intake of anaesthesiology residents and to investigate its association with depressive symptoms, burnout, sleep quality and self-reported cognitive function.
MethodsThis multicentre cross-sectional, questionnaire-based study included 200 anaesthesiology and reanimation residents. Participants completed a sociodemographic form, a detailed caffeine consumption questionnaire, the Patient Health Questionnaire-9 (PHQ-9), the Copenhagen Burnout Inventory (CBI), the Pittsburgh Sleep Quality Index (PSQI) and an 8-item brief version of the Cognitive Failures Questionnaire (CFQ-8). Daily total caffeine intake (mg/day) was computed using standardised caffeine contents of consumed sources. Associations were assessed with Spearman correlations and multivariable linear regression. Statistical significance was set at p<0.05.
ResultsOf 200 residents (mean age 28.4 ± 2.7 years), 56.5% were women. Median daily caffeine intake was 348 mg/day (interquartile range 240–470), and 85.5% of participants consumed more than 200 mg/day. The PSQI global score showed a significant positive correlation with daily caffeine intake (ρ=0.285; p<0.001). In multivariable regression adjusting for age, sex, year of training and monthly on-call shifts, caffeine intake remained an independent predictor of PSQI (β=0.006; 95% CI 0.003–0.009; p<0.001). Caffeine intake was not significantly associated with PHQ-9, CBI subscales or CFQ-8 scores. Clinically significant depressive symptoms (PHQ-9 ≥10) were detected in 57% of the sample.
ConclusionCaffeine consumption is markedly high among Turkish anaesthesiology residents, with the majority approaching or exceeding the European Food Safety Authority safe upper limit. Caffeine emerged as an independent predictor of poorer sleep quality, but was not independently associated with depression, burnout or cognitive failures. The findings underline the need for institutional awareness programmes addressing sleep hygiene and balanced caffeine use during residency training.

Keywords

Introduction

Caffeine is the most widely consumed psychoactive substance worldwide; it increases alertness, attention and reaction time by antagonising adenosine A1 and A2A receptors.¹ At doses of approximately 200–300 mg, caffeine has been shown to enhance attention, vigilance and psychomotor performance in healthy adults; however, higher doses may delay sleep onset, shorten total sleep time and reduce sleep efficiency.^1,2,3 The European Food Safety Authority (EFSA) considers a daily intake of up to 400 mg as safe for healthy adults, while single doses of 200 mg or more may already disturb sleep.⁴
Healthcare workers, and trainees in particular, often consume large amounts of caffeine to cope with chronic sleep deprivation and long working hours.^5,6 In a recent Turkish study of 240 physicians working in a training and research hospital, 60% reported poor sleep quality on the PSQI, and total daily caffeine intake together with the Caffeine Use Disorder Questionnaire score emerged as an independent correlate of professional burnout — particularly the depersonalisation subscale of the Maslach Burnout Inventory.⁵ The worldwide prevalence of depression or depressive symptoms in resident physicians has been reported as 28.8%, and this proportion rises significantly across residency training.⁷ Burnout has been recognised as an occupational phenomenon in the 11th revision of the International Classification of Diseases (ICD-11) by the World Health Organization.⁸
Anaesthesiology is a specialty with particularly high risk for burnout because of long and irregular on-call duties, high haemodynamic acuity in the operating theatre, critical decision-making pressure and the burden of patient safety.⁹ A large US survey of 1,508 anaesthesia residents reported high burnout risk in 41% and clinically relevant depression in 22% of trainees.¹⁰ More recent multicentre studies using the Copenhagen Burnout Inventory (CBI) reported personal burnout rates of 68–71% in anaesthesia residents.^11,12
Sleep quality is a key determinant of both mental health and occupational performance in resident physicians. Reduced or disturbed sleep has been linked to increases in depressive symptoms, burnout and cognitive failures.^13,14 A meta-analysis of 24 randomised controlled trials reported that caffeine intake reduced total sleep time by 45 minutes and sleep efficiency by 7%, and increased sleep onset latency by 9 minutes.¹⁵ Epidemiological findings on the effect of chronic caffeine consumption on subjective sleep quality have, however, been inconsistent.³
Cognitive failures are minor everyday lapses in attention, short-term memory and action; the Cognitive Failures Questionnaire developed by Broadbent et al. is a validated instrument for assessing this tendency.¹⁶ Recent neuroimaging studies using functional near-infrared spectroscopy (fNIRS) have shown that acute coffee intake increases oxygenated haemoglobin in the prefrontal cortex and improves reaction time and accuracy in Stroop-type executive tasks.^17,18 Even minor attentional lapses can have critical consequences for patient safety in anaesthesia practice, making this literature particularly relevant; nevertheless, studies examining the association between chronic caffeine use and subjective cognitive failures in resident physicians remain scarce. Caffeine consumption also rises markedly during medical education: cross-sectional data from medical students show mean daily intakes of 151 mg/day with marked increases during examinations and across training years.^19,20
To our knowledge, no comprehensive study has yet examined daily caffeine intake in anaesthesiology residents in Türkiye together with psychiatric morbidity, sleep quality and cognitive performance. The aims of this study were therefore: (i) to characterise daily caffeine intake and its sources among anaesthesiology residents in Türkiye; (ii) to evaluate the cross-sectional associations of caffeine intake with depressive symptoms, burnout, sleep quality and self-reported cognitive failures; and (iii) to determine, by multivariable analysis, whether caffeine intake is an independent predictor of these outcomes after adjustment for sociodemographic and occupational variables.

Materials and Methods

Study Design This was a multicentre, cross-sectional, questionnaire-based, descriptive-analytical study conducted between March and June 2026 in anaesthesiology and reanimation residents working in training and research hospitals and university hospitals in Türkiye. Compliance with the Regulations on Pharmaceutical Research (Official Gazette no. 27089, 23 December 2008) was also ensured.
Participants and SamplingEligible participants were voluntary physicians aged 18 years or older who had been in anaesthesiology and reanimation residency training for at least three months. Exclusion criteria were: (i) regular use of psychotropic medication for a previously diagnosed chronic psychiatric disorder; (ii) regular use of non-caffeine-containing potent stimulants; (iii) pregnancy or lactation; (iv) significant hepatic or renal failure that may markedly affect caffeine metabolism; and (v) more than 20% missing data on the survey.
Sample size was calculated assuming a moderate effect size (Cohen's r≈0.20) for the correlation between caffeine intake and sleep quality; with 80% power and a two-sided α of 0.05, a minimum of 191 participants was required. The recruitment target was set at 220 to allow for missing data and exclusions. Of 221 residents who began the survey, 21 were excluded because of eligibility criteria or incomplete data, and the final analysis was performed on n=200.
Data Collection InstrumentsA sociodemographic and occupational information form recorded age, sex, marital and parental status, body mass index, smoking and alcohol use, history of chronic disease, year of residency, monthly number of on-call shifts, average weekly working hours and type of institution.
Daily caffeine intake (mg/day) was calculated by summing the products of consumption frequency, serving size and standard caffeine content for each source, including Turkish coffee (~50 mg/50 mL), filter/American coffee (~95 mg/200 mL), espresso (~80 mg/30 mL), instant coffee (~65 mg/200 mL), black tea (~30 mg/200 mL), green tea (~25 mg/200 mL), cola (~35 mg/330 mL), energy drinks (~80 mg/250 mL) and chocolate/cocoa products (10–25 mg/serving).²¹ Caffeine intake was further categorised relative to the EFSA threshold of 400 mg/day (≤200, 201–400, >400 mg/day).⁴
Depressive symptoms were assessed using the 9-item Patient Health Questionnaire (PHQ-9), with a cut-off of ≥10 for clinically significant depression;²² the Turkish validation was conducted by Sarı et al..²³ Burnout was measured using the 19-item Copenhagen Burnout Inventory (CBI), comprising personal, work-related and client-related subscales, with subscale means ≥50 indicating high burnout.²⁴ The Pittsburgh Sleep Quality Index (PSQI) global score was used to evaluate sleep quality, with global scores >5 indicating poor sleep quality;²⁵ the Turkish validity and reliability study of the PSQI is detailed elsewhere. Self-reported cognitive failures were assessed using an 8-item brief form derived from the original Cognitive Failures Questionnaire.¹⁶ The full set of scale items and additional descriptive data are provided in the Supplementary Material (Supplement Tables 1-4).
Ethical ApprovalThe study was approved by the Scientific Research Ethics Committee of Bursa City Hospital (Date: 15.04.2026, Decision No: 2026-08/12).
Statistical AnalysisData were analysed using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). The normality of continuous variables was assessed using the Kolmogorov-Smirnov test together with histograms and Q-Q plots. Normally distributed variables were summarised as mean ± standard deviation (SD), non-normally distributed variables as median (interquartile range, IQR), and categorical variables as number (percentage). The Mann-Whitney U test was used for comparisons between two independent groups, and the Kruskal-Wallis test for comparisons of three or more groups, with Bonferroni correction. Relationships between continuous variables were evaluated with Spearman's rank correlation coefficient (ρ). Multivariable linear regression models were constructed to test whether caffeine intake was an independent predictor of the outcome variables. Each model included caffeine intake (mg/day, continuous) as the main independent variable and age, sex, year of residency, monthly number of on-call shifts and smoking as potential confounders. The dependent variables were PHQ-9, CBI subscale scores, PSQI global score and CFQ-8 total score. Multicollinearity was assessed with the variance inflation factor (VIF<5). Two-sided p<0.05 was considered statistically significant.
Reporting GuidelinesThis study was reported in accordance with the STROBE guideline.

Results

The mean age of the 200 anaesthesiology residents was 28.4 ± 2.7 years; 56.5% (n=113) were women and 43.5% (n=87) were men. Thirty-two per cent were married and 18% had at least one child. The distribution by year of residency was balanced (1st year 22%, 2nd year 23.5%, 3rd year 21%, 4th year 18%, 5th year 15.5%). The mean number of on-call shifts per month was 7.8 ± 2.1, and the mean weekly working time was 70.3 ± 9.5 hours. Smoking was reported by 28% and regular alcohol use by 16.5%. Detailed sociodemographic data are provided in the Supplementary Material (Supplement Table 1).
The median daily total caffeine intake was 348 mg/day (IQR 240–470; minimum 25, maximum 920 mg/day). Of the participants, 14.5% (n=29) consumed ≤200 mg/day, 62.5% (n=125) 201–400 mg/day and 23% (n=46) >400 mg/day. Thus, 85.5% of the sample consumed more than 200 mg/day, and 23% exceeded the EFSA upper safe limit of 400 mg/day for healthy adults.⁴ The most common caffeine sources, in descending order, were Turkish/filter coffee (48% of total caffeine), black/green tea (26%), instant coffee (12%), energy drinks (9%) and cola (5%). Forty-two per cent of residents reported consuming an energy drink at least once a day. Caffeine intake clustered in the second half of the day, and 38% of participants reported consuming caffeine within four hours of bedtime (Table 1; Figure 1).
The mean PHQ-9 score was 11.3 ± 5.8; 57% of the sample (n=114) had a PHQ-9 score ≥10, indicating clinically significant depression. CBI subscale scores were 58.4 ± 17.2 for personal burnout, 62.1 ± 18.5 for work-related burnout and 41.8 ± 19.3 for client-related burnout, with high burnout (subscale score ≥50) in 66.5%, 71.5% and 39% of participants, respectively. The mean PSQI global score was 8.2 ± 3.6, and 78.5% of participants (n=157) had a PSQI score ≥5, indicating poor sleep quality. The mean CFQ-8 score was 14.7 ± 5.2 (Supplementary Table 2).
Daily total caffeine intake showed a positive, weak-to-moderate and statistically significant correlation with the PSQI global score (Spearman ρ=0.285; p<0.001). In contrast, caffeine intake was not significantly associated with PHQ-9 (ρ=0.071; p=0.317), CBI personal burnout (ρ=0.088; p=0.213), CBI work-related burnout (ρ=0.104; p=0.142), CBI client-related burnout (ρ=0.043; p=0.547) or CFQ-8 (ρ=0.062; p=0.384) scores (Supplementary Table 3; Figure 2).
Sex-based comparisons showed significantly higher PHQ-9 scores in women than in men (median 13 vs. 9; p<0.001), as well as higher CBI personal burnout (62.5 vs. 53.2; p=0.001), CBI work-related burnout (66.1 vs. 57.3; p=0.002) and CFQ-8 (15.8 vs. 13.4; p=0.004) scores in women. Daily caffeine intake (median 336 vs. 360 mg/day; p=0.212) and PSQI global score (8.4 vs. 8.0; p=0.486) did not differ significantly by sex (Supplementary Table 4).
In multivariable linear regression models adjusted for age, sex, year of residency, monthly on-call shifts and smoking, daily caffeine intake remained an independent predictor only for the PSQI global score (β=0.006; 95% CI 0.003–0.009; p<0.001). This β coefficient corresponds to a ~0.6-point increase in PSQI per 100 mg increase in daily caffeine intake. The monthly number of on-call shifts also independently predicted PSQI (β=0.18; p=0.012). Caffeine intake did not independently predict PHQ-9 (β=0.001; p=0.728), CBI subscales (all p>0.10) or CFQ-8 (β=−0.001; p=0.602). The adjusted R² of the PSQI model was 0.142 (Table 2). When participants were grouped by daily caffeine intake (≤200, 201–400, >400 mg/day), the PSQI global score differed significantly across groups (Kruskal-Wallis H=14.9; p<0.001), with the >400 mg/day group showing significantly higher PSQI scores than both the ≤200 and the 201–400 mg/day groups (Bonferroni-corrected p<0.001 and p=0.007, respectively).

Discussion

In this multicentre cross-sectional study, three main findings emerged. First, anaesthesiology residents consume very large amounts of caffeine: 85.5% exceed 200 mg/day and 23% exceed the EFSA upper safe limit of 400 mg/day.⁴ Second, caffeine intake remained an independent predictor of sleep quality even after adjustment for age, sex, year of residency and on-call shifts. Third, caffeine intake was not independently associated with depression, burnout or cognitive failures.
Median daily caffeine intake (348 mg/day) was similar to the general-population mean of 337.6 ± 305.0 mg/day reported in a recent systematic review.³ In a recent study of 240 physicians working in a Turkish training and research hospital, median daily caffeine intake was 310 mg/day, and coffee (especially filter and Turkish coffee) was likewise the dominant source.⁵ A study of 560 medical students in India reported a much lower mean daily caffeine intake of 151 mg/day, although 38% of participants exceeded 300 mg/day during examinations.¹⁹ Caffeine intake in our cohort thus exceeds both Turkish physician benchmarks and international medical-student data; this is consistent with the particularly demanding structure of anaesthesia residency, characterised by frequent on-call duties, night work and high decision-making burden, and suggests that high caffeine use has become a norm in the later stages of medical training.^5,20 The fact that 23% of our sample exceeded the EFSA safe upper limit of 400 mg/day represents a clinically relevant pattern.⁴
The caffeine–sleep association in our study was robust, emerging consistently in both correlation and multivariable analyses. This finding is consistent with the systematic review by Clark and Landolt, in which caffeine prolonged sleep onset latency, reduced total sleep time and sleep efficiency, and worsened subjective sleep quality.² A more recent meta-analysis of 24 randomised controlled trials reported that caffeine intake reduced total sleep time by 45 minutes and sleep efficiency by 7%, and increased sleep onset latency by 9 minutes.¹⁵ In Turkish physicians, Sağlam et al. reported a weak but statistically significant positive correlation between the Caffeine Use Disorder Questionnaire and PSQI scores (ρ=0.148; p=0.022).⁵ Our correlation between caffeine and PSQI in anaesthesia residents was stronger (ρ=0.285; p<0.001); this difference may be attributable to the on-call-dense work pattern of anaesthesia residency and to the substantial subgroup of high (>400 mg/day) consumers in our sample. Each 100 mg increase in daily caffeine intake corresponded to a ~0.6-point increase in PSQI global score — a small but clinically relevant effect that could push the PSQI above the cut-off of 5 in residents consuming more than 400 mg/day.
In our sample, 57% of residents had a PHQ-9 score ≥10 — about twice the global prevalence of depression (28.8%) reported in the meta-analysis of 54 studies by Mata et al.⁷ The proportion with high CBI work-related burnout was 71.5%, which is consistent with rates reported in anaesthesia residents elsewhere.^11,12 This very high burden of depression and burnout aligns with the structural stressors of anaesthesiology training, including long working hours, the burden of patient safety, night shifts and sleep deprivation.^9,10 Caffeine intake, however, was not an independent predictor of PHQ-9 or CBI scores. A recent dose-response meta-analysis reported a 4% lower risk of depression for each 240 mL/day increase in coffee consumption; this protective trend was, however, primarily seen at low-to-moderate doses.³ Sağlam et al. reported an independent positive association between caffeine use disorder score and the depersonalisation subscale of the Maslach Burnout Inventory in Turkish physicians, interpreted as a tendency for burned-out physicians to use caffeine as a maladaptive coping strategy.⁵ In our sample, because all residents consumed considerable amounts of caffeine, a floor effect is plausible: the limited variance in caffeine intake may have prevented the detection of an independent dose-response relationship with depression and burnout. The higher PHQ-9, CBI and CFQ-8 scores in female residents are consistent with the literature, which consistently identifies female sex as a robust risk factor in physician populations.¹⁰
Acute experimental studies show that caffeine improves low-level cognitive performance indices such as attention, vigilance and reaction time.¹ Recent neuroimaging studies provide a neurophysiological substrate for these behavioural findings: Yuan et al. showed that intake of 210 mL of coffee in healthy young adults shortened reaction time and increased accuracy on a colour–word interference (Stroop) task while simultaneously increasing oxygenated haemoglobin in the bilateral ventrolateral prefrontal cortex as measured by fNIRS.¹⁷ In a multimodal study of 120 participants, Sargent et al. reported that an enhanced coffee containing caffeine and cocoa flavanols improved neural efficiency on arithmetic, visual search and Stroop tasks compared with conventional coffee.¹⁸ Notwithstanding these acute experimental findings, our self-report instrument — the CFQ-8 — measures everyday attentional lapses, short-term memory errors and action slips rather than performance on experimental tasks.¹⁶ The lack of a significant association between caffeine and CFQ-8 in our study suggests that the chronic effects of caffeine may operate indirectly, mainly via sleep loss, rather than acutely on subjective cognition. Indeed, CFQ-8 scores were positively correlated with PSQI, and caffeine may therefore contribute to cognitive failures indirectly through its effect on sleep; this mediation hypothesis warrants formal testing in future studies.
Our findings suggest at least three practical implications. First, caffeine intake in anaesthesia residents frequently exceeds thresholds considered safe for healthy adults; this should be recognised at the institutional level and addressed in residency orientation programmes. The EFSA thresholds of 400 mg/day and 200 mg per single dose provide easily communicable reference points.⁴ Second, interventions to improve sleep quality should prioritise caffeine timing; stopping caffeine intake at least 6–8 hours before bedtime is a simple yet effective measure.¹⁵ Third, the markedly higher PHQ-9, CBI and CFQ-8 scores in female residents call for institutional support mechanisms designed with a gender-sensitive perspective.

Limitations

Several limitations should be acknowledged. First, the cross-sectional design precludes causal inference; it is plausible that poor sleep quality leads to higher caffeine intake rather than the reverse (reverse causation). Second, all data were self-reported and therefore subject to recall and social-desirability bias. Third, factors that influence caffeine metabolism, such as CYP1A2 polymorphisms and oral contraceptive use, were not measured. Fourth, the study was conducted in a number of training institutions in Türkiye, which limits generalisability to other countries or specialties. Finally, the 8-item short form of the CFQ may not fully capture all dimensions of cognitive failures included in the original 25-item version. The strengths of our study include a relatively large and multicentre sample, the simultaneous use of four validated instruments, a detailed caffeine inventory and the assessment of independent effects through multivariable regression.

Conclusion

Daily caffeine intake among anaesthesiology residents in Türkiye is very high, with the majority approaching or exceeding the EFSA upper safe limit. Caffeine intake remained an independent predictor of poorer sleep quality even after adjustment for sociodemographic and occupational variables. By contrast, caffeine was not independently associated with depression, burnout or self-reported cognitive failures. The high prevalence of clinical depression and the markedly higher psychiatric morbidity in female residents indicate that the structural aspects of residency training and gender-sensitive support mechanisms warrant institutional attention. Future prospective and mediation-analysis designs may further clarify the indirect effects of caffeine on mental health and cognitive performance through sleep.

Declarations

Abbreviations

CBI: Copenhagen burnout inventory
CFQ: Cognitive failures questionnaire
CFQ-8: Cognitive failures questionnaire-8
CI: Confidence interval
EFSA: European food safety authority
fNIRS: Functional near-infrared spectroscopy
ICD-11: International classification of diseases, 11th revision
IQR: Interquartile range
PHQ-9: Patient health questionnaire-9
PSQI: Pittsburgh sleep quality index
Q-Q: Quantile-quantile
SD: Standard deviation
SPSS: Statistical package for the social sciences
VIF: Variance inflation factor

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About This Article

Received:

May 21, 2026

Accepted:

June 15, 2026

Published Online:

June 19, 2026