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Links between shift work, metabolic risk factors inconsistent across studies
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Adults who perform shift work are at increased risk for weight gain, overweight and impaired glucose tolerance; however, a systematic review found insufficient evidence to link shift work to other metabolic outcomes, according to research in the American Journal of Preventive Medicine.
Karin I. Proper, PhD, of the National Institute for Public Health and the Environment and VU University Medical Center in Amsterdam, and colleagues analyzed data from 39 articles on 22 longitudinal studies conducted between 1995 and March 2015 that examined body weight, glucose metabolism, lipid metabolism and blood pressure in adults who performed shift work vs. a nonshift working group. Studies that examined the relationship between shift work and metabolic syndrome, diabetes or cardiovascular disease were excluded. Researchers summarized data qualitatively per metabolic risk factor using a best-evidence synthesis; consistency was defined as at least 75% of the studies showing a similar result. Sample sizes ranged from fewer than 85 workers to 107,663 workers; occupational groups and shift work definitions varied.
Among the included studies, 17 examined the relationship between shift work and body weight-related outcomes; eight of those studies found a positive relationship between shift work and body weight or BMI, and seven studies found shift work to be a significant predictor of overweight. Due to mixed results, evidence for a relationship between shift work and waist circumference was inconsistent.
Nine of the studies examined the relationship between shift work and glucose metabolism; 75% of high-quality studies found shift work was a predictor for IGT. However, due to study inconsistencies, researchers found insufficient evidence to link shift work to increased total cholesterol or hypertension.
The researchers noted that some study inconsistencies could be attributed to poor scoring of shift work measurement and description; information about type and duration of shift work was missing in some studies.
“It is important to characterize the shift work schedule in as much detail as possible,” the researchers wrote. “Not just night shifts disturb sleep; in some cases, morning shifts disturb sleep patterns even more so than night shifts, because difficulty is experienced in initiating sleep early enough to obtain adequate sleep.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
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