Shift work aggravates metabolic syndrome development among early-middle-aged males with elevated ALT.
OBJECTIVE
To examine whether shift work accelerates metabolic syndrome (MetS) development among early middle-aged males with elevated alanine aminotransferase (e-ALT).


METHODS
A retrospective, observational follow-up study on MetS development at a 5-year interval was conducted using health examination data. Nine hundred and ninety six male employees not fulfilling MetS criteria at screening were enrolled. Age, MetS-components, liver enzymes, serological markers for viral hepatitis, abdominal ultrasound, insulin resistance status, lifestyles, and workplace factors were analyzed.


RESULTS
The prevalence of elevated serum ALT (> 40 U/L, e-ALT) at baseline was 19.1%. There were 381 (38.3%) workers with long-term exposures to day-night rotating shift work (RSW). 14.2% of subjects developed MetS during follow-up. After 5 years, the workers with e-ALT had significantly unfavorable changes in MetS-components, and higher rates of MetS development, vs subjects with normal baseline ALT levels. Workers with both baseline e-ALT and 5-year persistent RSW (pRSW) exposure had the highest rate of MetS development. Also, e-ALT-plus-pRSW workers had a significant increase in MetS-components at follow-up, compared with the other subgroups. After controlling for potential confounders, e-ALT-plus-pRSW workers posed a significant risk for MetS development (odds ratio, 2.7; 95% confidence interval, 1.4-5.3, vs workers without baseline e-ALT nor pRSW).


CONCLUSIONS
We suggest that all early middle-aged male employees with e-ALT should be evaluated and managed for MetS. Particularly in terms of job arrangements, impacts of long-term RSW on MetS development should be assessed for all male employees having baseline e-ALT.
Lin
Yu-Cheng
YC
Institute of Occupational Medicine and Industrial Hygiene, College of Public Health, National Taiwan University, Taipei, Taiwan, China.
Hsiao
Tun-Jen
TJ
Chen
Pau-Chung
PC
D000328:Adult; D000410:Alanine Transaminase / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D005500:Follow-Up Studies; D006801:Humans; D008019:Life Style; D008099:Liver / Q000000981:diagnostic imaging / Q000201:enzymology; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood / Q000503:physiopathology; D008875:Middle Aged; D016272:Occupational Health; D012189:Retrospective Studies; D018570:Risk Assessment; D011795:Surveys and Questionnaires; D014463:Ultrasonography; D014937:Work; D014940:Work Schedule Tolerance
D015415:Biomarkers; D000410:Alanine Transaminase