Relationship between shift work and hypercholesterolemia in Japan.
OBJECTIVE
The objective of this study was to clarify the influence of shift work on total cholesterol levels in serum in male Japanese workers.


METHODS
Pooled logistic regression analyses were applied in this 14-year cohort study of 5510 male workers in a steel company. In examining how the adjustments influenced the results, the effect of shift work on the onset of hypercholesterolemia (>or=220 mg/dl, 5.7 mmol/l) was calculated by adjusting only for age (step 1), for age and lifestyle factors (drinking habit, smoking habit, habitual exercise) (step 2), for age, body mass index (BMI), and the laboratory data [creatinine, glycosylated hemoglobin A1c (HbA1c), aspartic aminotransferase, gamma-glutamyl transpeptidase (gamma-GTP), uric acid] (step 3), and for age, BMI, lifestyle factors, and the laboratory data (step 4).


RESULTS
The odds ratio (OR) for shift work with respect to the onset of hypercholesterolemia was significant in step 4 [OR 1.10, 95% confidence interval (95% CI) 1.00-1.21, P-value 0.048], whereas the corresponding odds ratios in steps 1, 2, and 3 were not significant. In step 4, the other significant covariates were age (OR 1.01, 95% CI 1.00-1.02), BMI (OR 1.07, 95% CI 1.05-1.09), HbA1c (OR 1.07, 95% CI 1.02-1.11), gamma-GTP (OR 1.03, 95% CI 1.02-1.04) and alcohol consumption (OR 0.89, 95% CI 0.81-0.99).


CONCLUSIONS
In the present study, shift work was shown to be a potential risk factor for hypercholesterolemia among male Japanese workers. However, no consistent association was found between shift work and hypercholesterolemia in the hierarchical evaluation of the statistical model. The present study could not provide well-established evidence for a relationship between shift work and hypercholesterolemia.
Dochi
Mirei
M
Department of Occupational and Environmental Medicine (A2), Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba, 260-8670, Japan. muetani@faculty.chiba-u.jp
Sakata
Kouich
K
Oishi
Mitsuhiro
M
Tanaka
Kumihiko
K
Kobayashi
Etsuko
E
Suwazono
Yasushi
Y
D000328:Adult; D015331:Cohort Studies; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood / Q000453:epidemiology*; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012044:Regression Analysis; D012307:Risk Factors; D014940:Work Schedule Tolerance