Long working hours linked to underactive thyroid: Study

Adults who work long hours are more likely to have underactive thyroid, according to a study which may lead to better lifestyle and clinical recommendations for hyperthyroidism.

Earlier research has shown that hypothyroidism causes tiredness, depression, feeling cold, and weight gain.

The current study, published in the Journal of the Endocrine Society, found a higher risk of hypothyroidism with long working hours regardless of the workers' socioeconomic status or sex, even though this common thyroid disorder affects women more than men.

"Overwork is a prevalent problem threatening the health and safety of workers worldwide," said study co-author Young Ki Lee from the National Cancer Center in Goyang-si in South Korea.

"To our knowledge, this study is the first to show that long working hours are associated with hypothyroidism," Lee said.

In the study, the scientists assessed data from 2,160 adult full-time workers who participated in the Korea National Health and Nutrition Examination Survey from 2013 to 2015.

They identified hypothyroidism from records of the participants' thyroid blood analyses.

According to the study, hypothyroidism occurred at more than twice the rate in participants who worked 53 to 83 hours weekly versus those who worked 36 to 42 hours each week.

For each 10-hour increase in the workweek, the scientists said, individuals who worked longer hours had an increased odds for hypothyroidism compared with those who worked 10 hours less.

Lee cautioned that further studies are needed to determine whether long working hours cause hypothyroidism, which is a known risk factor for heart disease and diabetes.

"If a causal relationship is established, it can be the basis for recommending a reduction in working hours to improve thyroid function among overworked individuals with hypothyroidism," he said.

Lee added that screening for hypothyroidism could be easily integrated into workers' health screening programs using simple laboratory tests."