Overtime work and prevalence of diabetes in Japanese employees: Japan epidemiology collaboration on occupational health study.
OBJECTIVE
Epidemiologic evidence on long working hour and diabetes has been conflicting. We examined the association between overtime work and prevalence of diabetes among Japanese workers.


METHODS
The subjects were 40,861 employees (35,170 men and 5,691 women), aged 16 to 83 years, of 4 companies in Japan. Hours of overtime were assessed using self-reported questionnaires. Diabetes was defined as a fasting plasma glucose ≥126 mg/dl (7.0 mmol/l), hemoglobin A1c ≥6.5% (48 mmol/mol), or current use of anti-diabetic drug. Multiple logistic regression analysis was used to calculate odds ratio of diabetes for each category of overtime.


RESULTS
After adjustment for age, sex, company, smoking, and BMI, there was a suggestion of U-shaped relationship between overtime work and prevalence of diabetes (P for quadratic trend = 0.07). Compared with those who worked <45 hours of overtime per month, the adjusted odds ratios (95% confidence interval) of diabetes were 0.86 (0.77-0.94), 0.69 (0.53-0.89), and 1.03 (0.72-1.46) for those who worked 45-79, 80-99, and ≥100 hours of overtime per month, respectively. In one company (n = 33,807), where other potential confounders including shift work, job position, type of department, alcohol consumption, sleep duration, leisure time physical activity, and family history of diabetes was additionally adjusted for, similar result was obtained (P for quadratic trend = 0.05).


CONCLUSIONS
Long hours of overtime work may not be associated with increased prevalence of diabetes among Japanese workers.
Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
Keisuke
K
Kuwahara
Azbil corporation, Tokyo, Japan.
Teppei
T
Imai
Azbil corporation, Tokyo, Japan.
Akiko
A
Nishihara
Hitachi, Ltd., Ibaraki, Japan.
Tohru
T
Nakagawa
Hitachi, Ltd., Ibaraki, Japan.
Shuichiro
S
Yamamoto
Hitachi, Ltd., Ibaraki, Japan.
Toru
T
Honda
Nippon Steel & Sumitomo Metal Corporation Kimitsu Works, Chiba, Japan.
Toshiaki
T
Miyamoto
Furukawa Electric Corporation, Tokyo, Japan.
Takeshi
T
Kochi
Furukawa Electric Corporation, Tokyo, Japan.
Masafumi
M
Eguchi
YAMAHA CORPORATION, Shizuoka, Japan.
Akihiko
A
Uehara
The University of Tokyo, Tokyo, Japan.
Reiko
R
Kuroda
Mitsubishi Heavy Industries, Ltd., Aichi, Japan.
Daisuke
D
Omoto
Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
Kayo
K
Kurotani
Department of Epidemiology, Faculty of Public Health, Thai Nguyen University of Medicine and Pharmacy, Thai Nguyen Province, Vietnam.
Ngoc Minh
NM
Pham
Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
Akiko
A
Nanri
Furukawa Electric Corporation, Tokyo, Japan.
Isamu
I
Kabe
Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
Tetsuya
T
Mizoue
National Institute of Public Health, Saitama, Japan.
Naoki
N
Kunugita
Mitsui Chemicals, Inc., Tokyo, Japan.
Seitaro
S
Dohi
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003920:Diabetes Mellitus / Q000453:epidemiology* / Q000209:etiology*; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016272:Occupational Health; D016017:Odds Ratio; D015995:Prevalence; D012307:Risk Factors; D014940:Work Schedule Tolerance; D016526:Workload; D055815:Young Adult