A new study provides further health concerns for the estimated 20 million Americans who sleep during the daytime because of their work schedule. The symptoms of untreated obstructive sleep apnea may be worse for shift workers, a new study reports.

The study compared a group of 31 shift workers to ten daytime workers. Members in both groups were previously diagnosed with sleep apnea and had similar ages, weights and sleep lengths.

Daytime and nighttime polysomnograph results show that the shift workers had more frequent breathing pauses in breathing and higher oxygen desaturation levels. Both measures show that shift workers had more severe symptoms of sleep apnea.

The authors of the study caution that patients with untreated sleep apnea should avoid nighttime work. The Sleep Education Blog urges workers with sleep apnea to take that warning one step further and never let sleep apnea go untreated. Sleep apnea has been linked to heart disease, diabetes, dementia and other serious health problems.

Shift work also can also harm your health. Some workers may struggle with shift work disorder, which causes your internal body clock to go awry. Workers with shift work disorder may be severely tired but unable to sleep. Loss of sleep length and quality may affect job performance and put workers at risk for injury.

Read more about obstructive sleep apnea and shift work disorder.