Physiological and psychological impacts on male medical interns during on-call duty

Figures & data

Figure 1.  Study design. Participants were aware of this study's intention to obtain objective and subjective evaluations of their performance (CPT), autonomic functioning (HRV), sleepiness (ESS; SSS), and emotional state (HADS). The on-call day comprised routine work from 7:30 to 17:00, followed by OCD for 15 h. The on-call phase lasted for 3 days, one cycle after another; these were the pre-call day, the on-call day, and post-call day. Measurements were obtained during the third month of the internal medicine course. After 3 months, the tests were repeated during the third month of a duty-free course and this was used as a self-control group.

Table I.  Regression coefficients and SD resulting from the construction of a linear mixed-effect model of the HRV among all participants during the awake period.

	Dependent variable
Independent variable	RR (ms)	HF [ln(ms^2)]	LF [ln(ms^2)]	LF/HF [ln(ratio)]
Intercept	487.3(15.2)	3.53(0.153)	6.03(0.119)	2.51(0.086)
Internal medicine course vs. duty-free course	54.2(13.7)*	0.224(0.140)	0.126(0.109)	0.080(0.079)
Duty night work vs. on-call daytime work	− 4.09(14.7)	0.253(0.153)	0.046 (0.120)	− 0.230(0.086)*
Post-call vs. on-call daytime work	− 20.0 (16.1)	0.054(0.165)	− 0.012(0.129)	− 0.092(0.093)
Pre-call vs. on-call daytime work	− 24.4(14.9)	− 0.285(0.156)	− 0.253(0.123)*	0.028(0.087)
ln (activity)	− 55.7(2.15)**	− 0.346(0.024)**	− 0.149(0.020)**	0.201(0.013)**

Note: RR, R–R interval from electrocardiogram; HF, high-frequency; LF, low-frequency components from fast Fourier transformation. *P < 0.05; **P < 0.001.

Table II.  Regression coefficients and SD resulting from the construction of a linear mixed-effect model of the HRV among all participants during the sleep period.

	Dependent variable
Independent variable	RR (ms)	HF [ln(ms^2)]	LF [ln(ms^2)]	LF/HF [ln(ratio)]
Intercept	548.4(39.9)	4.69(0.327)	9.23(0.383)	4.77(0.318)
Internal medicine course vs. duty-free course	22.4(18.4)	− 0.127(0.144)	− 0.234(0.102)*	− 0.332(0.117)*
on-call vs. pre-call	− 33.6(18.7)	0.249(0.151)	− 0.009(0.120)	− 0.133(0.130)
Post-call vs. pre-call	8.36(18.7)	0.555(0.149)*	0.192(0.113)	− 0.048(0.125)
ln (activity)	− 72.1(6.25)**	− 0.249(0.052)**	0.386(0.065)**	0.658(0.053)**

Note: RR, R–R interval from electrocardiogram; HF, high-frequency; LF, low-frequency components from fast Fourier transformation. *P < 0.05; **P < 0.001.

Table III.  Comparison of the sleep time and CPT results across the different time points.

	NOC	PreO	OCD	PostO
Sleep time (h) (n = 13)	6.12 ± 0.917	6.67 ± 1.18	5.04 ± 0.776*	6.31 ± 1.69
CPT (n = 8)
Omissions (times)	1.00 ± 1.25	7.00 ± 17.8	1.38 ± 1.51	0.625 ± 1.06
Commissions (times)	12.9 ± 7.50	26.1 ± 6.51**	21.3 ± 11.0	22.8 ± 5.75
Hit RT (ms)	313.0 ± 29.8	275.3 ± 19.9**	308.4 ± 74.6	295.2 ± 30.6
Preservation (times)	0.125 ± 0.232	0.625 ± 0.744	1.50 ± 2.73	2.75 ± 5.01
Hit RT block change	0.008 ± 0.014	0.004 ± 0.019	0.005 ± 0.016	0.008 ± 0.019
Hit RT ISI change	0.041 ± 0.022	0.056 ± 0.019	0.043 ± 0.024	0.046 ± 0.014

Note: NOC, non-on-call, PreO, pre-call, OCD, on-call duty, PostO, post-call; Hit RT, hit reaction time; Block, change across duration of test; ISI, inter-stimulus interval. Results are expressed as mean ± SD. *P < 0.05 compared with NOC; **P < 0.01 compared with NOC by Dunn's multiple comparison test.

Figure 2.  ESS and SSS scores for internal medicine and duty-free course. (A) ESS scores for the NOC and OCD phases. (B) SSS scores for control noon (NOC-D), pre-call noon (PreO-D), on-call noon (OCD-D), on-call night (OCD-N), post-call morning (PostO-M), and post-call noon (PostO-D). The results are expressed as Mean ± SD. ††P < 0.01 compared with NOC by Wilcoxon signed rank test, n = 9. *P < 0.05 compared with NOC-D; **P < 0.01 compared with NOC-D; #P < 0.05 compared with PreO-D by Dunn's multiple comparison test, n = 9. The SSS data for NOC duty and pre-call noon were the average of day 1 and day 4 during the internal medicine course and the average of day 1 and day 2 during duty-free course, respectively.

Figure 3.  HADS scores and subscale scores for internal medicine and duty-free course. (A) HADS scores, (B) HADS-anxiety [HADS (A)] subscale scores, (C) HADS-depression [HADS (D)] subscale scores for NOC, pre-call (PreO), on-call (OCD), and post-call (PostO) duty. Results are expressed as Mean ± SD. *P < 0.05 compared with NOC; ***P < 0.001 compared with NOC; #P < 0.05 compared with PreO; ##P < 0.01 compared with PreO by Dunn's multiple comparison test, n = 11.

Figure 4.  Commissions and Hit RT of CPT for internal medicine and duty-free course. (A) Commissions, which were made when a response is given to a nontarget, as measured by the CPT, (B) Hit RT, the average speed of the correct responses for the entire test, as measured by the CPT for NOC, pre-call (PreO), on-call (OCD), and post-call (PostO) duty. The results are expressed as Mean ± SD. **P < 0.01 compared with NOC by Dunn's multiple comparison test; n = 8.