Association of overtime work and obesity with needle stick and sharp injuries in medical practice

Table 1 Characteristics of study participants according to their medical specialty and professional grade

Variable	Totaln	NSIs			Female			Age		HBW			Moderate OT			Heavy OT
		n	%	P1	n	%	P1	mean ± SD	P2	n3	%	P1	n	%	P	n	%	P1
Profession groups
Doctors	104	8	7.7	a	28	26.9	c	40.9 ± 10.4	c	53	51.0	NS	31	29.8	b	17	16.3	c
Nurses	613	16	2.6		588	95.9		33.6 ± 8.3		354	57.8		147	24.0		28	4.6
Others	130	5	3.9		95	73.1		40.6 ± 7.1		64	49.2		15	11.5		0	0.0
Profession grade (doctor)
AP	71	1	1.4	b	14	19.7	a	45.5 ± 9.3	c	33	46.5	NS	22	31.0	b	6	8.5	b
RD	33	7	21.2		14	42.4		31.0 ± 2.9		20	60.6		9	27.3		11	33.3
Profession grade (nurse)
N	129	8	6.2	3	119	92.2	NS	25.3 ± 3.3	c	78	60.5	NS	42	32.6	a	6	4.7	NS
N1	134	1	0.8		128	95.5		29.0 ± 4.9b		70	52.2		35	26.1		3	2.2
N2	145	3	2.1		140	96.6		34.6 ± 6.7		84	57.9		24	16.6		9	6.2
N3	143	4	2.8		140	97.9		40.5 ± 6.5		86	60.1		29	20.3		6	4.2
N4	62	0	0		61	98.4		42.3 ± 4.8		36	58.1		17	27.4		4	6.5

^aP < 0.05.

^bP < 0.01.

^cP < 0.0001.

NS: Not significant.

¹Chi-square test or Fisher’s exact test.

²Moderate overtime work is 45–80 h/mo, and heavy overtime work is > 80 h/mo.

³Overweight/Obesity.

OT: Overtime; NSIs: Needle stick and sharps injuries.

Table 2 Main effects on needle stick and sharps injuries in different models for all participants

Main effect		ORs of NSIs for All participants				ORs of NSIs for doctors				ORs of NSIs for nurses
		N	n	M0	M1	N	n	M0	M2	N	n	M0	M2
Body weight level	HBW	471	11	0.5NS	0.5a	53	2	0.3	0.2a	354	7	0.6	0.5
	UHBW	376	18	1.0	1.0	51	6	1.0	1.0	259	9	1.0	1.0
OT work	Heavy	45	6	5.7b	4.3a	17	4	5.4a	2.0	28	2	3.7	3.8
	Moderate	193	7	1.4	1.2	31	1	0.6	0.5	147	5	1.7	1.4
	Mild	609	16	1.0	1.0	56	3	1.0	1.0	438	9	1.0	1.0
Type of medical personnel	Doctors	104	8	2.1	1.3	-	-	-	-	-	-	-	-
	Nurses	613	16	0.7	0.3a	-	-	-	-	-	-	-	-
	Others	130	5	1.0	1.0	-	-	-	-	-	-	-	-
Professional grade (Doctors)	RD	-	-	-	-	33	7	18.9b	17.3a	-	-	-	-
	AP	-	-	-	-	71	1	1.0	1.0	-	-	-	-
Professional grade (Nurses)	Junior	-	-	-	-	-	-	-	-	129	8	3.9b	3.9b
	experiencing	-	-	-	-	-	-	-	-	484	8	1.0	1.0

^aP < 0.05.

^bP < 0.01.

^cP < 0.0001.

NS: Not significant.

Odds ratio = 1.0 indicates the reference; ORs: Odds ratios; N: Participants; n: Participants for needle stick and sharps injuries; M₀: Model only including main effect; M₁: Model adjusted for sex, age, overtime work, and medical specialty; M₂: Model adjusted for sex (only doctors), overtime work, professional grade, and body weight; HBW: Healthy body weight; UHBW: Unhealthy body weight; OT: Overtime; NSIs: Needle stick and sharps injuries.

Table 3 Main effects on needle stick and sharps injuries in various models for resident doctors and junior nurses

Main effect		N	ORs for NSIs
			n	M0	M1	M2
Body weight level	HBW	95	3	0.1b	0.1b	0.1b
	UHBW	52	12	1.0	1.0	1.0
OT work	Heavy	13	4	4.5a	4.5a	1.9
	Moderate	46	5	1.6	1.6	1.7
	Mild	88	6	1.0	1.0	1.0
Professional subfield	RD	26	7	4.1a	12.7b	19.5a
	JN	121	8	1.0	1.0	1.0

^aP < 0.05.

^bP < 0.001.

Odds ratio = 1.0 indicates the reference. ORs: Odds ratios; N: Participants; n: Participants for needle stick and sharps injuries; M₀: Model only including the main effect; M₁: Model adjusted for sex and age; M₂: Model adjusted for sex, age, and main effects; RD: Resident doctor; JN: Junior nurse; HBW: Healthy body weight; UHBW: Unhealthy body weight; OT: Overtime; NSIs: Needle stick and sharps injuries.

Table 4 Main effects on needle stick and sharps injuries for experienced nurses

Main effect		Participants		ORs for NSIs
			n	M0	M1
Body weight level	HBW	276	5	1.3	1.2
	UHBW	208	3	1.0	1.0
OT work	Heavy	22	2	7.0a	6.6a
	Moderate	105	1	0.7	0.7
	Mild	357	5	1.0	1.0

^aP <0.05.

Odds ratio = 1.0 indicates the reference. ORs: Odds ratios; HBW: Healthy body weight; OT: Overtime; NSIs: Needle stick and sharps injuries; n: Participants for needle stick and sharps injuries; M₀: Model only including the main effect; M₁: Model adjusted for age, sex, body weight, and overtime work.

Table 5 Mediation effect of heavy overtime work and healthy body weight for needle stick and sharps injuries and the main effect

IV	Mediator factor
	Heavy OT work4							HBW5
	c	c’	a	sa	b	sb	Zm	c’	a	sa	b	sb	Zm
All participants
Doctors1	1.1a	0.8	1.6c	0.3	1.4b	0.5	2.5*	1.0a	-0.2	0.2	-0.7NS	0.4	0.8
Doctors effect
RD2	2.9b	2.6a	1.7b	0.6	1.1	0.8	1.2	3.3b	0.6	0.4	-1.8a	0.9	-1.1
Nurse effect
JN3	1.4b	1.4b	0	0.5	1.2	0.8	0	1.4b	0.1	0.2	-0.6	0.5	-0.4

^aP < 0.05.

^bP < 0.01.

^cP < 0.0001.

NS: Not significant.

¹Reference variable includes nurses and others.

²Reference variable is Aps.

³Reference variable is experienced nurses.

⁴Reference variable includes moderate overtime and slight overtime.

⁵Reference variable is unhealthy body weight.

IV: Independent variable; RD: Resident doctor; JN: Junior nurse; HBW: Healthy body weight.