More hypothyroidism seen among adults with longer workweeks
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Hypothyroidism was more than 2.5 times more prevalent among Korean adults who worked between 53 and 83 hours per week than those who worked between 36 and 42 hours per week.
Additionally, those who worked longer hours increased their likelihood for hypothyroidism by 46% for each additional 10 hours they worked per week, according to data accepted for presentation at the Endocrine Society Annual Meeting and published in Thyroid.
“The adverse health impact of long working hours has been well established regarding cardiovascular diseases,” Young Ki Lee, MD, a specialist in the division of endocrinology and metabolism in the department of internal medicine at the National Cancer Center in Goyang, South Korea, told Healio. “There is increasing epidemiologic evidence that long working hours are also associated with adverse metabolic and mental health outcomes, such as diabetes mellitus, obesity, metabolic syndrome, fatigue and depressive symptoms. Hypothyroidism is associated with many other diseases, including atherosclerotic cardiovascular disease, congestive heart failure, diabetes mellitus, obesity, metabolic syndrome, fatigue and depression, which have large overlaps with overworkrelated health outcomes.”
Lee and colleagues assessed data on work hours and thyroid function from 2,160 nonpregnant adults (mean age, 42.4 years; age range, 33-52.1 years; 69.9% men) who worked between 36 and 83 hours per week and who had no history of thyroid disease or thyroid peroxidase antibodies. Data were from the Korea National Health and Nutrition Examination Survey collected between 2013 and 2015. A serum thyroid-stimulating hormone level between 0.62 mIU/L and 6.86 mIU/L with a free thyroxine level between 0.89 ng/mL and 1.76 ng/mL was considered euthyroid.
Hypothyroidism was more than 2.5 times more prevalent among Korean adults who worked between 53 and 83 hours per week than those who worked between 36 and 42 hours per week.
Most of the study population was euthyroid (94.94%); 0.05% had overt hypothyroidism, 2.1% had subclinical hypothyroidism, 2.75% had subclinical hyperthyroidism and 0.16% had overt hyperthyroidism. The median workweek was 47.1 hours with 15.4% of the cohort doing shift work. About half of the cohort were college graduates (46.4%), 43.4% were office workers, 18.7% were service workers and 37.8% were manual workers.
Workers with hypothyroidism accrued more hours per week than euthyroid workers (P = .032), and a greater percentage of workers with hypothyroidism (64.8%) had a workweek longer than 48 hours vs. euthyroid workers (43.2%) and those with hyperthyroidism (52.4%; P = .024). Among those with hypothyroidism, 3.6% worked between 53 and 83 hours per week, whereas 1.4% worked between 36 and 42 hours per week. The adjusted OR for hypothyroidism and longer work hours was 1.46 (95% CI, 1.12-1.9) per 10-hour increase per week. Hyperthyroidism was not significantly associated with number of work hours. Results were consistent for groups based on sex, occupation, income level and education, according to the researchers.
“Many epidemiological studies have investigated the deleterious effects of overwork on workers’ health. However, laboratory assays were limited in many previous epidemiologic studies. We think that this may be the reason why the relationship between working hours and thyroid function was not reported,” Lee said. “The results of our study suggest that it may be helpful to consider the possibility of hypothyroidism while assessing the health of individuals working long hours.”
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