Relationship Between Rotating Night Shift Work and Anthropometric Markers of Overall and Central Adiposity

Figures & data

Table 1 Sociodemographic Characteristics and Health-Related Behaviors of the Studied Workers (n=647)

Characteristic	Frequency		95% CI^^
	No.	%
Age (years)
<30	97	15.0	(12.1, 17.8)
30-<40	376	58.1	(54.4, 62.1)
40-<50	131	20.2	(17.2, 23.5)
≥ 50	43	6.6	(4.7, 8.6)
Residence
Urban	480	74.2	(70.8, 77.5)
Rural	167	25.8	(22.5, 29.2)
Level of education
Never been to school	9	1.4	(0.6, 2.3)
Basic primary education	45	7.0	(5.0, 8.9)
High school	396	61.2	(57.4, 65.0)
Higher education	197	30.4	(26.8, 33.9)
Marital status
Never married	93	14.4	(11.6, 17.3)
Married	533	82.4	(79.5, 85.3)
Divorced	21	3.2	(2.0, 4.7)
Smoking status
Never been smoker	230	35.5	(31.8, 39.5)
Ex-smoker	56	8.7	(6.5, 10.8)
Current smoker	361	55.8	(51.7, 59.9)
Smoking intensity^#
Light	175	48.5	(43.5, 53.2)
Moderate	114	31.6	(26.6, 36.2)
Heavy	72	19.9	(15.9, 24.6)
Physical activity
No	602	93.0	(90.9, 94.9)
Yes	45	7.0	(5.1, 9.1)
Self-rated health
Poor	7	1.1	(0.3, 2.0)
Fair	136	21.0	(17.8, 24.3)
Good	482	74.5	(71.0, 77.8)
Very good	22	3.4	(2.1, 4.8)

Notes: ^{^}CI, confidence interval of the percent, ^#Intensity of smoking was determined by calculating the smoking index (SI) among current smokers (n=361), by multiplying the number of cigarettes smoked per day by the number of smoking years, then, categorized into: light (SI <200), moderate (SI: 200–400), and heavy (SI >400).

Table 2 Occupational Characteristics and Anthropometric Markers of Overall and Central Adiposity Among the Studied Workers (n=647)

Characteristic	Frequency		95% CI^^
	No.	%
Occupational characteristics
Job duration (years)^#
<10	507	78.4	(75.2, 81.6)
10-<20	97	15.0	(12.3, 18.1)
≥20	43	6.6	(4.8, 8.5)
Job nature
Blue collar	526	81.3	(78.4, 84.5)
White collar	111	17.2	(14.0, 20.1)
Pink collar	10	1.5	(0.6, 2.6)
Work schedule
Daytime work	174	26.9	(23.3, 30.4)
RNS	473	73.1	(69.6, 76.7)
Years of RNS
0	174	26.9	(23.5, 30.7)
1–5	169	35.7	(31.5, 40.0)
6–9	213	45.0	(40.7, 49.5)
≥ 10	91	19.2	(15.7, 22.9)
Anthropometric markers of adiposity
BMI (kg/m^2)
Underweight (<18.5)	2	0.3	(0.0, 0.8)
Normal (18.5 to 24.9)	68	10.5	(8.1, 12.8)
Overweight (25 to 29.9)	283	43.7	(39.9, 47.2)
Obese (≥ 30)	294	45.4	(41.7, 49.3)
Waist circumference (cm)
Adequate	255	39.4	(35.8, 43.4)
Increased^$	392	60.6	(56.6, 64.2)

Notes: ^{^}CI, confidence interval of the percent, ^#Job duration refers to the whole duration of employment. ^$Waist circumference ≥ 94 cm for men.

Abbreviation: RNS, rotating night shift.

Table 3 Anthropometric Markers of Overall and Central Adiposity Among the Studied Workers Stratified by the Work Schedule (n=647)

Adiposity Markers	Work Schedule								P-value^a
	Daytime Workers (n=174)		RNS Workers (n=473)^&
			1–5 Years of RNS (n= 169)		6–9 Years of RNS (n= 213)		≥10 Years of RNS (n= 91)
	No.	% (95% CI)	No.	% (95% CI)	No.	% (95% CI)	No.	% (95% CI)
BMI (kg/m^2)
<30	98	56.3 (49.5, 64.4)	103	60.9 (53.3, 68.2)	105	49.3 (42.9, 56.0)	47	51.6 (41.0, 61.4)	0.125
≥ 30	76	43.7 (35.6, 50.5)	66	39.1 (31.8, 46.7)	108	50.7 (44.0, 57.1)	44	48.4 (38.6, 59.0)
Waist circumference
Adequate	65	37.4 (30.0, 44.1)	81	47.9 (40.6, 56.0)	77	36.2 (30.0, 42.9)	32	35.2 (25.3, 44.7)	0.068
Increased^#	109	62.6 (55.9, 70.0)	88	52.1 (44.0, 59.4)	136	63.8 (57.1, 70.0)	59	64.8 (55.3, 74.7)

Notes: ^#Waist circumference ≥ 94 cm for men. ^&RNS workers (n=473) were classified according to the total number of years of RNS during career into three groups: 1–5 years; 6–9 years; and 10 years or more of working RNS. ^aMonte Carlo test.

Abbreviations: RNS, rotating night shifts; BMI, body mass index; CI, confidence interval of the percent.

Table 4 Univariate Logistic Regression of Overall Adiposity (BMI ≥ 30 Kg/m²) Associated with the Work Schedule Among the Studied Workers (n=647)

Work Schedule	Overall Adiposity				OR^# (95% CI)	P-value
	Yes (n=577)		No (n=70)
	No.	%	No.	%
Daytime work^^	76	25.9	98	27.8	Ref.	-
1–5 years of RNS	66	22.4	103	29.2	0.82 (0.53, 1.27)	0.385
6–9 years of RNS	108	36.7	105	29.7	1.32 (0.88, 1.98)	0.169
≥ 10 years of RNS	44	15.0	47	13.3	1.20 (0.72, 2.01)	0.468

Notes: ^#Univariate logistic regression was conducted to compute the odds of overall adiposity (BMI ≥ 30 kg/m²) (dependent variable) associated with the work schedule (independent variable). ^{^}Reference category.

Abbreviations: BMI, body mass index; RNS, rotating night shifts; OR, odds ratio; CI, confidence interval.

Table 5 Multivariate Logistic Regression of Independent Predictors of Increased BMI (≥ 25 Kg/m²) Among the Studied Workers (n=647)

Variables	Coefficient	Adjusted OR^†	95% CI	P-value
Work schedule
Daytime work^^	Ref.	Ref.	Ref.	Ref.
1–5 years of RNS	−0.181	0.835	(0.38, 1.82)	0.650
6–9 years of RNS	−0.585	0.557	(0.26, 1.17)	0.126
≥ 10 years of RNS	2.016	7.512	(0.93, 60.67)	0.059
Age (years)
<30^^	Ref.	Ref.	Ref.	Ref.
30-<40	0.961	2.613	(1.35, 5.05)	0.004**
40-<50	1.102	3.011	(1.19, 7.56)	0.019*
≥ 50	0.861	2.366	(0.57, 9.82)	0.236
Education
Unschooling or basic education	−0.376	0.687	(0.28, 1.76)	0.435
High school or higher education^^	Ref.	Ref.	Ref.	Ref.
Residence
Urban area	−1.063	0.346	(0.16, 0.74)	0.007**
Rural urea^^	Ref.	Ref.	Ref.	Ref.
Physical activity^#
No	−0.421	0.656	(0.23, 1.86)	0.430
Yes^^	Ref.	Ref.	Ref.	Ref.
Smoking
Never been smoker	0.765	2.149	(1.12, 4.11)	0.021*
Ex-smoker	−0.665	0.514	(0.22, 1.15)	0.107
Current smoker^^	Ref.	Ref.	Ref.	Ref.
Job nature^&
Pink-collar	−0.596	0.551	(0.08, 3.6)	0.538
Blue-collar	0.538	1.712	(0.81, 3.59)	0.156
White-collar^	Ref.	Ref.	Ref.	Ref.

Notes: Model X² =47.15 (p <0.001). Nagelkerke’s R²=0.14; Cox & Snell R²= 0.07; Hosmer & Lemeshow X²=7.433 (p=0.491). ^#Physical activity was reported according to the WHO recommendation of at least 150–300 minutes of moderate-intensity, or 75–150 minutes of vigorous-intensity physical activity each week. ^&White-collar jobs, including supervisory and managerial, professional or semiprofessional, and business owner roles; pink-collar jobs, including hospitality and administration roles, retail workers, office clerks, and salesperson roles; and blue-collar jobs, including laborer and skilled trade roles. ^†OR adjusted for all variables in the above table ^{^}Reference category. *p value ≤ 0.05. **p value ≤ 0.01.

Abbreviations: RNS, rotating night shifts; OR, odds ratio; CI, confidence interval.

Table 6 Univariate Logistic Regression of Central Adiposity (Wait Circumference ≥ 94 Cm) Associated with the Work Schedule Among the Studied Workers (n=647)

Work Schedule	Central Adiposity				OR^# (95% CI)	P-value
	Yes (n=392)		No (n=255)
	No.	%	No.	%
Daytime work^^	109	27.8	65	25.5	Ref.	-
1–5 years of RNS	88	22.4	81	31.8	0.64 (0.42, 0.99)	0.048
6–9 years of RNS	136	34.7	77	30.2	1.05 (0.69, 1.59)	0.807
≥ 10 years of RNS	59	15.1	32	12.5	1.09 (0.64, 1.86)	0.725

Notes: ^#Univariate logistic regression was conducted to compute the odds of central adiposity (waist circumference ≥ 94 cm) (dependent variable) associated with the work schedule (independent variable). ^{^}Reference category.

Abbreviations: RNS, rotating night shifts; OR, odds ratio; CI, confidence interval.

Table 7 Multivariate Logistic Regression of Independent Predictors of Increased Waist Circumference (≥ 94 Cm) Among the Studied Workers (n=647)

Variables	Coefficient	Adjusted OR^†	95% CI	P-value
Work schedule
Daytime work^^	Ref.	Ref.	Ref.	Ref.
1–5 years of RNS	0.045	1.046	(0.64, 1.70)	0.856
6–9 years of RNS	0.288	1.334	(0.83, 2.14)	0.233
≥ 10 years of RNS	−0.070	0.932	(0.51, 1.68)	0.816
Age (years)
<30^^	Ref.	Ref.	Ref.	Ref.
30-<40	1.084	2.955	(1.80, 4.83)	<0.001***
40-<50	1.598	4.945	(2.64, 9.25)	<0.001***
≥ 50	1.905	6.718	(2.73, 16.48)	<0.001***
Education
Unschooling or basic education	0.243	1.275	(0.66, 2.46)	0.469
High school or higher education^^	Ref.	Ref.	Ref.	Ref.
Residence
Urban area	0.134	1.144	(0.78, 1.67)	0.491
Rural urea^^	Ref.	Ref.	Ref.	Ref.
Physical activity^#
No	−0.232	0.793	(0.40, 1.54)	0.497
Yes^^	Ref.	Ref.	Ref.	Ref.
Smoking
Never been smoker	0.198	1.219	(0.84, 1.75)	0.286
Ex-smoker	0.049	1.050	(0.57, 1.91)	0.873
Current smoker^^	Ref.	Ref.	Ref.	Ref.
Job nature^&
Pink-collar	−0.555	0.574	(0.13, 2.37)	0.443
Blue-collar	−0.361	0.697	(0.42, 1.14)	0.157
White-collar^	Ref.	Ref.	Ref.	Ref.

Notes: Model X² =43.396 (p <0.001). Nagelkerke’s R²=0.08; Cox & Snell R²= 0.06; Hosmer & Lemeshow X²=5.99 (p=0.541). ^#Physical activity was reported according to the WHO recommendation of at least 150–300 minutes of moderate-intensity, or 75–150 minutes of vigorous-intensity physical activity each week. ^&White-collar jobs, including supervisory and managerial, professional or semiprofessional, and business owner roles; pink-collar jobs, including hospitality and administration roles, retail workers, office clerks, and salesperson roles; and blue-collar jobs, including laborer and skilled trade roles. ^†OR adjusted for all variables in the above table ^{^}Reference category. ***p value ≤ 0.001.

Abbreviations: RNS, rotating night shifts; OR, odds ratio; CI, confidence interval.