Effects of prolonged working hours on heart rate variability in internal medicine physicians | Scientific Reports - Nature.com

Prolonged moving implicit 24 h is not uncommon among physicians. This signifier could pb to slumber deprivation, emotional, and carnal accent which person been shown to impact enactment show and summation complaint of aesculapian errors¹. Not lone undermining patient’s safety, prolonged displacement enactment tin disturb sleep–wake cycle, eating patterns, societal life, and summation hazard of ischemic bosom disease². There were galore methods utilized to measure intelligence accent astatine work, specified arsenic ocular analog scale³, and Job Content Questionnaire⁴. Searching for the due appraisal tools to measurement intelligence and physiological accent astatine enactment whitethorn assistance understanding, and facilitate probe into accent simplification interventions which whitethorn amended short- and/or semipermanent outcomes for some patients and physicians.

Heart complaint variability (HRV) is the fluctuation successful the clip intervals betwixt adjacent heartbeats. HRV reflects regularisation of autonomic balance, cardiovascular, cardinal nervous, endocrine, and respiratory systems, circadian rhythm, baroreceptors, and chemoreceptors⁵. A steadfast bosom has beat-to-beat variations which indicates the flexibility successful adapting to biology oregon biopsychosocial challenges. HRV tin beryllium measured successful ultra-short-term (< 5 min), short-term (< 24 h), and 24-h investigation and tin beryllium described arsenic time-domain, frequency-domain, and non-linear measurements. Studies person been shown that debased HRV is associated with precocious occupation strain⁶, nighttime shift⁷, oregon 24-h shift^8,9, and is besides a marker of accrued cardiovascular risks^10,11.

Most of the information among physicians and wellness unit were constricted to HRV monitored during 24-h displacement oregon less. The information regarding HRV during prolonged moving hours beyond 24 h are scarce. Therefore, we aimed to measurement HRV successful physicians who were the interior medicine grooming during extended moving hours beyond 24-h call, arsenic compared to their regular 8-h moving day. In addition, we sought to find the imaginable factors associated with the HRV alterations successful this population. The prevalence of cardiac arrhythmias during mean moving hours and aft prolonged moving hours was besides examined.

Study plan and participants

This is simply a cross-sectional study. The volunteered interior medicine residents, interns, externs (age 18–35 years) who had 32-h moving periods successful Maharaj Nakorn Chiang Mai Hospital, Chiang Mai, Thailand, were enrolled successful the survey during a play from June 2020 to June 2022. We excluded the participants who utilized alcohol, caffeine, stimulant drug, oregon baccy wrong 8 h anterior to the enrollment. Those with underlying diseases were besides excluded.

Data collection

All subjects underwent Holter ECG monitoring (24-h Holter GE Seer Light Extend, GE Medical Systems, Suzuken Company, Limited, Nagoya, Aichi, Japan) for HRV appraisal utilizing MARS® Holter Analysis Workstation. In the interior medicine training, a regular workday starts astatine 8am to 4 pm. An on-call work starts astatine 4 pm to 8am the adjacent morning. At the extremity of on-call duty, the doctors indispensable proceed a regular workday from 8 americium to 4 pm. Therefore, connected the time of on-call duty, the doctors are compelled to continuously enactment for a full of 32 h (8am to 4 pm connected the adjacent day). In the contiguous study, we compared betwixt the HRV of an 8-h regular workday (8am to 4 pm) earlier on-call work (pre-call HRV) and the 8-h workday aft 24-h on-call work (post-call HRV) arsenic shown successful Fig. 1. Clinical information were utilized, including age, gender, duration of moving hours and duration of sleeping hours.

Figure 1

Flow of survey comparing 8-h HRV connected the time earlier and aft on-call duty.

Definitions

Heart complaint variability

Time-domain and frequency-domain analyses were performed according to the modular guidelines. Time-domain HRV indexes were analyzed utilizing statistical methods. The quadrate basal of the mean squared differences of successive normal-to-normal (NN) intervals (RMSSD), the modular deviation (SD) of each NN intervals (SDNN), the SD of the mean NN intervals calculated implicit 5-min periods of the full signaling (SDANN), and the proportionality of adjacent NN intervals differing by > 50 ms (pNN50) were measured.

Frequency-domain HRV were analyzed utilizing autoregressive powerfulness spectral investigation applied to the RR interval clip series. The pursuing spectral bands were identified: debased frequence (LF) (0.04–0.15 Hz), and precocious frequence (HF) (0.15–0.4 Hz). Total powerfulness (0–0.5 Hz) and the areas beneath each highest was calculated successful implicit units (ms²). Total powerfulness (TP) is the sum of the vigor successful the precise debased frequence (VLF), LF, and HF bands for HRV signaling little than 24 h, and represents the planetary autonomic activity¹².

The contiguous survey was registered astatine thaiclinicaltrials.org and the recognition fig is TCTR20210903003. This survey was approved by the Faculty of Medicine Ethical Committee with the support fig 268/2564. The probe was performed according to the Declaration of Helsinki. Informed consent was obtained from each participants.

Statistical analysis

Sample size calculation

We estimated the illustration size utilizing the estimation of a two-sample paired-means trial to comparison the quality of HRV parameters utilizing SDNN during 8-h earlier on-call work and during 8-h aft on-call duty. The presumption is based connected a erstwhile survey by Borchini and colleagues¹³ which recovered that the prolonged precocious occupation strain colonisation had SDNN of 128.3 ± 30.7 ms during the moving time and 142.4 ± 28.5 ms during the resting day. We acceptable alpha arsenic 0.05 and the powerfulness of the trial arsenic 90% (beta = 0.10). With this regard, the calculated illustration size was 50 subjects. We anticipated that 20% of Holter ECG information whitethorn person been uninterpretable by method error. Therefore, the estimated illustration size was 60 patients.

Data analysis

Results were expressed arsenic mean ± SD unless different specified. The numerical information were compared by utilizing paired T-test method. The comparisons of HRV parameters betwixt groups were adjusted according to imaginable confounding variables. Multivariate analyses were performed utilizing the aggregate linear regression. Each variables included successful the aggregate linear regression were checked for independency utilizing Eta directional measures oregon Pearson correlation to debar multicollinearity. Mann–Whitney U trial and Wilcoxon signed-rank trial were utilized if information were not usually distributed. We utilized two-way repeated measures investigation of variance (ANOVA) with pre- and post-call arsenic within-subject factor, and full slumber clip quartile arsenic between-subject factor. If the covariance matrix does not look to person compound symmetry, we analyzed information utilizing generalized estimating equation (GEE). P values of < 0.05 were considered statistically significant. Statistical bundle bundle SPSS mentation 21 was utilized for analysis.

Ethics support and consent to participate

Effects of prolonged moving hours connected bosom complaint variability successful interior medicine physicians was approved by the morals committee of the Faculty of Medicine, Chiang Mai University, support fig 268/2564. The investigations were carried retired successful accordance with the Declaration of Helsinki, including written informed consent of each participants.

Baseline characteristics

A full of 60 physicians successful the interior medicine grooming were enrolled successful the study. Baseline objective characteristics and objective information are shown successful Table 1. The mean property of the wide colonisation was 26.0 ± 2.5 years. Majority were females (53.3%). The mean tallness was 165.5 ± 9.1 cm. The mean assemblage value was 61.1 ± 14.6 kg. The mean assemblage wide scale (BMI) was 22.1 ± 3.6 kg/meters². The mean humor unit was 116.6 ± 11.4/72.6 ± 8.6 mmHg. The mean bosom complaint was 78.0±10.7 /min. The mean full slumber clip was 238.9 ± 88.3 min. The mean full awake per nighttime was 3 ± 2 times. Of the 60 physicians, 15 (25%) were externs, 10 (17%) were interns, and 35 (48%) were residents.

The HRV pre-call time and post-call day

Table 2 shows the examination betwixt pre- and post-call time successful wide volunteers. We demonstrated that some time- and frequency-domain HRV parameters did not disagree betwixt pre- and post-call day.

Factors associated with pre- and post-call HRV alterations

We included gender, BMI, full slumber time, and mean HR into the aggregate linear regression model. The SBP, age, and occupation relation were excluded from the exemplary due to the fact that of interdependence with BMI and full slumber time. Interestingly, we identified full slumber clip during connected telephone arsenic an autarkic origin associated with SDNN, SDANN, LF, HF, and LF/HF ratio (Table 3).

In Table 4, two-way repeated measures ANOVA and GEE demonstrated statistically important enactment betwixt full slumber clip and assorted pre/post telephone HRV parameters, including SDNN, SDANN, pNN50, LF, HF, and LF/HF ratio. This suggests that antithetic full slumber clip could impact pre-/post- telephone HRV alterations differently. When divided full slumber clip into 4 quartiles, determination were 18 physicians successful the 1st quartile (total slumber time ≤ 180 min) and 15 physicians successful the 4th quartile (total slumber time ≥ 307.5 min). Baseline pre-call HRV parameters betwixt 1st and 4th quartile was not statistically different. The physicians successful the 1st quartile had important summation successful post-call SDNN, pNN50, HF, and alteration successful LF/HF ratio arsenic compared to pre-call values (Table 4). While the physicians successful the 4th quartile had wholly other results, with important alteration successful RMSSD, pNN50, LF, HF, and summation successful mean HR arsenic compared to pre-call values (Table 4).

Cardiac arrhythmia

There was nary important arrhythmia observed successful our population.

There were 3 main findings from our study: 1) In wide population, determination were nary statistically important quality successful SDNN, SDANN, RMSSD, pNN50, LF, HF, LF/HF, TP, and mean HR betwixt pre-call and post-call; 2) Total slumber clip is an autarkic origin associated with pre and post-call HRV alterations; and 3) Physicians successful the interior medicine grooming who slept ≤ 180 min had antithetic post-call HRV alteration signifier arsenic compared to the physicians who slept ≥ 307.5 min.

Although our colonisation were each physicians successful interior medicine grooming with the aforesaid on-call duration (24 + 8 h), they whitethorn person somewhat antithetic roles depending connected the level of training, and varying full slumber clip depending connected fig of caller admissions and patient’s condition. Dutheil and colleagues measured HRV during the displacement and showed that exigency physicians who worked a 24-h displacement had importantly higher carnal strain, higher intelligence fatigue, and little parasympathetic enactment (reflected by little RMSSD) than ones who worked a 14-h shift⁹. Therefore, differing existent moving clip among individuals whitethorn person obscured the existent effects connected HRV successful our population.

We recovered full slumber clip an autarkic origin associated with pre and post-call HRV alterations. This is accordant with Bourdillon et al. survey which showed a important interaction of slumber deprivation connected HRV parameters¹⁴.

Not lone is full slumber clip during the displacement affecting the HRV, but besides the measuring play is crucial. Activities (rest astatine home, during shift, regular workday), clip of the time (day oregon night), and signaling duration (range from 2 min to 24 h) each could impact HRV results. It is important to stress that our survey is antithetic from astir erstwhile studies which measured HRV during < 24-h displacement work. Instead, we measured HRV connected post-call time aft physicians worked a 24-h telephone and had to proceed moving connected post-call time for further 8 h (24 + 8).

Among the physicians who were categorized successful the 4th quartile of full slumber clip (> 307.5 min), the PNN50, LF, HF were importantly decreased and mean HR was importantly accrued during post-call arsenic compared to pre-call workday. Nevertheless, determination was a nonsignificant inclination toward accrued LF/HF ratio during post-call arsenic compared to pre-call workday. This reflected the greater simplification of HF than LF successful those with longer slumber time. LF/HF ratio has been reported to estimation sympathovagal balance. A debased LF/HF ratio reflects greater parasympathetic enactment comparative to sympathetic activity, portion a precocious LF/HF ratio whitethorn bespeak higher sympathetic activity⁵. HF and pNN50 are intimately correlated with parasympathetic tense strategy (PNS) activity, and full vagal blockade has been shown to destruct HF oscillations¹⁵. LF set could beryllium influenced by some the PNS and sympathetic tense system(SNS) with assorted grade depending connected activities and conditions⁵. Therefore, the physicians successful the agelong slumber radical whitethorn person had an summation successful SNS enactment and PNS withdrawal. This corresponded with the summation successful the post-call mean HR successful this radical of physicians. As a result, TP worth successful 4th quartile slumber radical whitethorn look unchanged owed to other absorption of SNS and PNS activity. Our results successful the 4th quartile radical (more slumber time) lucifer the results from respective studies among residents, surgeons, and exigency physicians which showed little LF, little HF, little HRV, and higher mean HR during on-call day^6,7,9. In summation to little HRV, immoderate studies revealed either higher LF/HF ratio oregon urine noradrenaline, suggesting predominant SNS enactment during connected telephone day^7,9,16. Pichot et al. reported a alteration successful pNN50, LF, HF, and an summation successful HR arsenic a parasympathetic withdrawal signifier from cumulated carnal fatigue astatine the workplace¹².

Interestingly, we recovered the divergent results among the 1st quartile full slumber clip radical (≤ 180 min). There was a important summation successful SDNN, pNN50, HF, and alteration successful LF/HF, which whitethorn person reflected the higher PNS activity⁵. These findings were successful opposition to immoderate studies that reported a alteration successful HF, LF⁷, and summation successful LF/HF ratio^7,9 among physicians during connected call, accordant with a sympathetic dominance. This whitethorn beryllium explained by antithetic on-call duration (< 24 h successful different studies vs 24 + 8 h successful our study), and antithetic signaling conditions (during < 24 h connected telephone successful different studies vs during other 8 moving hours station 24-h call). Langelotz et al. measured HRV successful surgeons during a 24-h displacement and demonstrated akin findings to our survey that SDNN, RMSSD, pNN50, LF, and HF accrued astatine the extremity of the 24-h shift⁸. This differing HRV effect besides seen successful 1 survey who reported a simplification successful PNS enactment (RMSSD) aft low-intensity cycling, arsenic opposed to an summation successful PNS enactment aft high-intensity cycling¹⁷. The enactment betwixt SNS and PNS is complex. While an summation successful SNS enactment tin suppress PNS, higher oregon overwhelming SNS enactment whitethorn pb to PNS reactivity oregon “parasympathetic rebound⁵”. This improvement whitethorn explicate our findings of accrued SNS and suppressed PNS enactment among much slumber radical (> 5 h), arsenic compared to parasympathetic rebound among little slumber radical (< 3 h). Total powerfulness successful little slumber radical had an expanding inclination post-call time which could beryllium owed to PNS activation. Parasympathetic rebound measured by HRV was antecedently described successful long-distance motortruck drivers and it was associated with sleepiness portion driving¹⁸. We are the archetypal to study HRV successful physicians portion moving an other 8 h aft a 24-h displacement work. The results were intriguing particularly a PNS rebound among physicians who slept little than 3 h during connected call. Whether this uncovering is simply a marker of sleepiness oregon exceeding body’s limits needs further investigations. In aesculapian field, sleepiness successful physicians has been shown to associated with accrued aesculapian errors¹⁹. Moreover, nighttime displacement works adversely affected temper profiles (vigor-activity, anger-hostility, and fatigue-inertia) among residents²⁰.

The strengths of our survey are: 1) There were studies connected HRV successful surgeons, exigency physicians, and mixed specialties residents. We specifically looked astatine physicians successful the interior medicine training; 2) Most studies recorded HRV among physicians during 24-h displacement but we are the archetypal to grounds HRV alteration aft the extended 24-h shift. Therefore, providing accusation regarding effects of prolonged moving hr connected HRV; 3) We compared HRV betwixt pre- and post-call time from 8 to 4 pm which eliminated the differing power of carnal activities connected the circadian changes successful bosom complaint and humor pressure^21,22, fixed that the 2 signaling periods had akin carnal activities; and 4) We recorded HRV during 8-h moving period. Therefore, it provided a focused HRV accusation lone during work, and excluded during remainder oregon sleep.

Limitations see but not constricted to: 1) We did not measurement HRV during 24-h telephone to enactment the proposal of SNS overactivity that yet pb to parasympathetic rebound; 2) We did not measurement short-term objective effects of HRV alterations, specified arsenic affectional distress, carnal stress, sleepiness score, cognitive function, oregon aesculapian mistake incidence; 3) We did not execute further autonomic relation assessments to enactment the circumstantial correlation betwixt each HRV parameters and autonomic tense strategy activity. However, information connected idiosyncratic HRV metrics corresponding to autonomic tense strategy dynamics has been antecedently described successful literatures⁵; 4) Sleep clip was not measured directly, hence expanding hazard of self-report and callback bias. We attempted to trim these biases with nary request oregon desirable characteristics, prospective design, in-person interview, and abbreviated magnitude of callback play (immediate station call); and 5) We conducted a pre-post survey plan that had a azygous limb and was considered arsenic a self-controlled study. We could not wholly exclude the effects from confounding factors which occurred astir the aforesaid clip arsenic the involution (on call). However, by utilizing the aforesaid instruments measured lone 1 time isolated successful the aforesaid moving play (8am-4 pm) and environments, the observed post-call HRV changes were mostly attributed to the on-call intervention.

References

Authors and Affiliations

1. Division of Cardiology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand

   Teerapat Nantsupawat, Pongsatorn Tungsuk, Siriluck Gunaparn, Arintaya Phrommintikul & Wanwarang Wongcharoen

Contributions

T.N. performed the statistical analyses, evaluated the results and drafted the paper. P.T. and S.G. recruited patients and collected data. A.P. contributed substantially to information mentation and prime assurance. W.W. designed study, participated successful the conception and plan of the survey revised the insubstantial for important world content. All authors person work and approved the last manuscript.

Corresponding author

Correspondence to Wanwarang Wongcharoen.

Competing interests

The authors state nary competing interests.

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