한국성인의 수면시간과 갑상샘 질환 사이의 관계성에 대한 성별차이

Sex Difference in the Association between Sleep Duration and Thyroid Disease among South Korean Adults

Article information

J Health Info Stat. 2021;46(3):337-343
Publication date (electronic) : 2021 August 31
doi : https://doi.org/10.21032/jhis.2021.46.3.337
1Undergraduate Student, Department of Healthcare Management, Eulji University, Sungnam, Korea
2Professor, Department of Healthcare Management, Eulji University, Sungnam, Korea
3Graduate Student, Department of Healthcare Management, Eulji University, Sungnam, Korea
안정현1, 남진영,2, 박수진3
1을지대학교 의료경영학과 학부생
2을지대학교 의료경영학과 교수
3을지대학교 의료경영학과 석사과정생
Corresponding author: Jin Young Nam 553 Sanseongdae-ro, Sujeong-gu, Seongnam 13135, Korea Tel: +82-31-740-7451, E-mail: jynam@eulji.ac.kr
Received 2021 July 12; Revised 2021 August 22; Accepted 2021 August 25.

Abstract

목적

본 연구는 한국 성인의 수면시간과 갑상샘 유병률의 관계성에 대해 성별 차이를 파악하고자 한다.

방법

본 단면연구는 2016년부터 2018년까지 국민건강영양조사에 참여한 성인 17,555명이 포함되었다. 수면시간은 3가지로 분류하였다(불충분한 수면, 7시간 미만; 정상 수면, 7-8시간; 장시간 수면, 9시간 이상). 일반적 특성을 측정하기 위해 카이제곱 검정을 실시하였다. 일반적 특성과 갑상샘 질환 유병률 간의 관계를 확인하기 위해 다중 로지스틱 회귀분석을 사용하였다. 하위그룹 분석에서, 다중 로지스틱 회귀분석은 성별에 따라 수면시간과 갑상샘 질환 유병률 간의 관계성을 알기 위해 시행되었다.

결과

불충분한 수면과 장시간의 수면을 취한 남성은 정상 수면과 비교하였을 때 갑상샘 질환의 위험성이 증가하였다(불충분한 수면: OR=1.85, 95% CI=1.19-2.87; 장시간 수면: OR=1.71, 95% CI=1.02-2.87).

결론

본 연구는 불충분하고 장시간의 수면을 취한 남성은 갑상샘 질환과 관련성이 있다. 추후 연구에서는 성별에 따른 수면시간과 갑상샘 질환의 관계성을 수면의 질과 함께 고려할 필요가 있다.

Trans Abstract

Objectives

The study aimed to investigate sex differences associated with sleep duration and the prevalence of thyroid disease among South Korean adults.

Methods

This cross-sectional study included 17,555 adults who participated in the Korea National Health and Nutrition Examination Survey from 2016 to 2018. Sleep duration was categorized into three groups (insufficient, < 7 hour; normal, 7-8 hour; prolonged, ≥ 9 hour). A chi-squared test was performed to assess baseline characteristics. Multiple logistic regression analysis was used to identify the association between general characteristic and the prevalence of thyroid disease. In subgroup analysis, multiple logistic regression analysis was performed to find the association between sleep duration and prevalence of thyroid disease by sex.

Results

For men, insufficient and prolonged sleep durations were increased risk of thyroid disease compared with normal sleep duration (insufficient sleep: odds ratio, OR = 1.85, 95% confidence interval, CI = 1.19-2.87; prolonged sleep: OR = 1.71, 95% CI = 1.02-2.87).

Conclusions

This study found that men with insufficient and prolonged sleep were associated with thyroid disease. Further studies are needed to identify the relationship between sleep duration, thyroid disease, and sleep quality by sex.

INTRODUCTION

Sleep is an important component of health status. Although many people recognize that sleep is essential for life, they do not complete the required sleep duration due to social, leisure, or business-related activi-ties [1]. If the situation persists, it can negatively affect lifestyle and men-tal status and can lead to the occurrence of several diseases. In particular, insufficient sleep aggravates depression, physical health, immune, car-diovascular, and metabolic syndrome [2]. It affects patients with chronic pain and physical and psychological symptoms [3]. Sleep is related to an increased risk of mortality [4] and affects metabolic syndrome by sex [5]. Increased risk of all-cause mortality such as ischemic heart disease, other heart disease, cerebrovascular accidents, cancer, suicide and homicide were associated with short and long sleep duration [4]. Concerning met-abolic syndrome, men are associated with short sleep duration, and women are affected by long sleep duration [5]. Therefore, it is essential to sleep properly to maintain adequate sleep duration and prevent diseases.

There are many thyroid diseases such as autoimmune disease and Graves’ disease, which cause hyperthyroidism and Hashimoto's thyroid-itis, which results in hypothyroidism [6]. Based on the reference range of serum thyroid stimulating hormone (TSH) (0.62-6.68 mIU/L), the prev-alence of subclinical hypothyroidism and subclinical hyperthyroidism was 0.73% (0.40% men, 1.10% women) and 3.10% (2.26% men, 4.04% women), respectively, in Korea, from 2013-2015 [7]. Previous studies have investigated the association between sleep and thyroid diseases [8]. Sleep can affect hormone secretion, thyroid dysfunction, subclinical hyperthy-roidism, and subclinical hypothyroidism [8]. Insufficient sleep indicated a significantly increased risk of subclinical hyperthyroidism not hypo-thyroidism; however, prolonged sleep were elevated risk of subclinical hyperthyroidism and hypothyroidism [8]. A previous study indicated an increase in serum concentrations of fT3 and fT4 among individuals with sleep restriction compared to normal sleepers [9]. Furthermore, acute partial sleep deprivation has been shown to be influenced by en-docrine homeostasis, health, and wellbeing status [9].

Although numerous studies have shown the associations between sleep duration and thyroid hormones, little is known about whether sleep durations were associated with thyroid disease. Further, few studies have investigated the association between sleep duration and the preva-lence of thyroid disease according to sex. Thus, our study examined sleep duration and thyroid disease according to sex among South Kore-an adults, using data from the Korea National Health and Nutrition Ex-amination Survey (KNHANES) from 2016 to 2018.

METHODS

Study population and database information

The KNHANES is a national questionnaire designed to analyze the health and nutrition stations among Koreans and is often used as pri-mary data. The questionnaire provides objective and standardized sources while estimating the prevalence of diseases, conditions, and risk behaviors [10]. The study data were extracted from the seventh KNHANES, conducted from 2016-2018. First, 24,269 participants were identified from the KNHANES VII-3. We excluded the data collected from participants who were <19 years (n=4,880), cases with missing in-formation concerning the average sleep time per day during the weekday (n=1,116) and weekend (n=1), as well as cases involving no responses concerning average sleep time per day during the weekday (n=711) and the weekend (n=6). After excluding the data, 17,555 individuals (7,641 men, 9,914 women) were included in this study.

Definition of thyroid disease

Thyroid disease includes autoimmune disease, Graves’ disease, Hashi-moto's thyroiditis, hyperthyroidism, and hypothyroidism [6]. In this study, participants were classified as having thyroid diseases and not having thyroid disease. Thyroid disease was defined as participants who responded “ yes” to the following questions from the KNHANES: 1) Have you been diagnosed with thyroid disease by a physician? 2) Are you currently suffering from thyroid disease? Following these questions, individuals were defined as having thyroid disease diagnosed by a physi-cian and currently suffering from thyroid disease. Participants without thyroid disease were defined as individuals who answered “ no” to the above-mentioned questions.

Assessment of sleep duration

Sleep duration was assessed by the following questions: (1) On the week-day, what time did you go to sleep and wake up? (2) On the weekend, what time did you go to sleep and wake up? Using these questions, we calcu-lated the average sleep duration on weekdays and weekends. We classi-fied individuals into three groups according to previous research [11]: in-sufficient sleepers (<7 hour/day), normal sleepers (7-8 hour/day), and prolonged sleepers (≥9 hour/day).

Covariates

The following covariates were obtained using a standardized question-naire in the KNHANES: sex, age, household income, education, marital status, current smoking, high-risk alcohol consumption, body mass in-dex, working hours, physical activity, and year. The participants were stratified by age into five groups: 19-29 years, 30-39 years, 40-49 years, 50-59 years, and ≥60 years of age. The participants were stratified by household income into four categories: low, low-moderate, moderate-high, high. The individuals were divided by education into four groups: ele-mentary school, middle school, high school, and college and above. Cur-rent smoking was defined as participants who smoked >100 cigarettes in their lifetime and current smokers [12]. High-risk alcohol consumption was defined as the consumption of more than 14 drinks per week for men and 10 drinks per week for women [11]. Body mass index (BMI) was stratified into three groups: underweight (BMI<18.5 kg/m2), normal (18.5 kg/m2 ≤BMI<25 kg/m2), and obese (BMI≥25 kg/m2) [13]. Working hours per week were classified into five groups: not working, <20, 20-39, 40-59, and ≥60 [14]. Physical activity was defined as moderate-in-tensity physical activity for more than 150 minutes per week, high level of physical activity for more than 75 minutes, or a mix of moderate-and high-intensity physical activity [15].

Statistical analysis

We assessed the association between sleep duration and the prevalence of thyroid disease according to sex. A chi-squared test was performed to assess baseline characteristics. Multiple logistic regression analyses were performed to calculate odds ratio (OR) and 95% confidence interval (CI) for general characteristic and thyroid disease. Sleep duration and thyroid disease according to sex were used for multiple logistic regression analy-ses. Statistical significance was set at p <0.05. SAS 9.4 (SAS Institute Inc., Cary, NC, USA) was used for all statistical analyses.

Ethical approval

The KNHANES VII was approved by the institutional review board of the Korea Centers for Disease Control and Prevention for the 3rd year (2018-01-03-P-A).

RESULTS

The general characteristics of the study population are summarized in Table 1. The study included 7,641 men and 9,914 women. There were 685 and 16,870 patients with and without thyroid disease, respectively. The prevalence of thyroid disease was 1.4% and 5.8% in men and women, re-spectively. Approximately, 4.1%, 3.8%, and 3.8% of the cases involving in-sufficient sleep, normal sleep, and prolonged sleep were associated with the prevalence of thyroid disease. Statistical significance was observed for sex, age, marital status, current smoking, and working hours among participants with thyroid disease (p-value <0.0001, respectively).

General characteristics of study population in the Korea National Health and Nutrition Examination Surveys 2016-2018

Table 2 shows that the association between general characteristic and thyroid disease among South Korean adults. Women were statistically significant for thyroid disease (OR=4.52, 95% CI=3.56-5.73). However, the prevalence of thyroid disease was not associated with sleep duration.

The association between general characteristic and prevalence of thyroid disease among Korean adults in the Korean National Health and Nutrition Examination Surveys 2016-2018

In the subgroup analysis, We compared sex differences in the association between sleep duration and the prevalence of thyroid disease among South Korean adults (Figure 1). Among men, insufficient sleep (OR=1.85, 95% CI=1.19-2.87) and prolonged sleep (OR=1.71, 95% CI=1.02-2.87) were associated with the prevalence of thyroid disease; however, the same was not observed for women.

Figure 1.

The sex difference in the association between sleep duration and prevalence of thyroid disease among South Korean adults. Results are demonstrated odds ratios and 95% confidence intervals. Adjusted for age, household income, education, marital status, current smoking, high-risk alcohol consumption, body mass index, working hours, physical activity, and sleep duration.

DISCUSSION

The results of the present study demonstrated that sleep duration was not associated with the prevalence of thyroid disease. However, we found that there was a sex difference between sleep duration and the preva-lence of thyroid disease. In subgroup analysis, insufficient and prolonged sleep was related to the risk of thyroid disease for men. However, no sta-tistically significant association was observed in women.

Most previous studies have confirmed the effects of sleep on various diseases and mortality, including cardiometabolic health [1], depression [16], chronic pain [3], increased risk of death [17], myriad adverse behav-ioral consequences [2] and metabolic syndrome [5]. Based on those studies, our study defined 7-8 hours as adequate sleep duration which was found to be preventive factor for thyroid disease. However, few studies have investigated the influence of sleep on thyroid function by sex, and there is a lack of information concerning the topic.

In previous studies, subclinical thyroid disease was associated with short and long sleep durations [8]. Based on this study, short sleep was increased in hyperthyroidism; however, the same was not observed in hypothyroidism. Further, short sleep was associated with a high proba-bility of TSH suppression. Long sleep duration was associated with in-creased TSH secretion and subclinical hypothyroidism. In addition, both short sleep and long sleep are increased in hyperthyroidism [8].

Although there are few studies detailing sleep duration and thyroid disease, several studies have shown that changes in serum concentrations of thyroid stimulating hormone (TSH), free triiodothyronine (fT3), and free thyroxine (fT4) were controlled by circadian rhythm and partial sleep and they impacted secretory activity and thyroid function [9,1820]. Several studies have evaluated the influence of sleep on TSH, fT3, and fT4, which are affected by thyroid and other diseases [9]. In previous studies, women were higher 24 h-fT4 concentrations than men. In both men and women, partial sleep loss was related to a decline in free T4 and TSH; however, the results indicated that women had a statistically signif-icant association [20]. Ferdinand [19] showed that elderly men had lower average nocturnal TSH levels compared to young individuals. In these sleep loss studies, sleep restriction for two consecutive nights among young men influenced the thyrotrophic axis [9]. Serum concentrations of fT3 and fT4 were increased, and serum TSH levels were slightly ele-vated in the evening hours [9]. Additionally, studies of thyrotropin secretion profiles demonstrated that TSH concentrations were slightly higher in men than in women at night [18].

According to our results, sleep duration was not associated with the prevalence of thyroid disease compared to a previous study [8]. A previous study explained that sleep duration exerted an influence on subclinical hyperthyroidism and subclinical hypothyroidism with thyroid hormone [8]. Further, our study indicated a statistical significance for men, when the correlation between insufficient sleep and prevalence of thyroid dis-ease was analyzed by sex. Our study data from KNHANES 2016-2018 were not investigated for serum concentrations of TSH, fT3, and fT4. We could not confirm the mechanism underlying the association between sleep duration and the prevalence of thyroid disease. Therefore, our study is based on several previous studies. Thus, more studies are required to examine the influence of sleep duration on thyroid disease by sex, sleep quality, large population, and nationally representative data.

This study had several strengths. First, this study used a nationally representative sample with a large population compared to previous studies. To our knowledge, this is the first study detailing sex difference between sleep duration and the prevalence of thyroid disease. Second, various covariables were used in our studies and defined as thyroid dis-ease with physician diagnosis and current prevalence to ensure precise measurement. Third, we investigated the wakeup time and bedtime on weekdays and weekends, respectively, using KNHANES questionnaires. Using these individuals'sleep time, we calculated the average sleep duration on weekdays and weekends.

However, there are some limitations to our study. First, sleep quality was not analyzed in the present study. The sleep quality and sleep duration affected thyroid disease [2124], so it should be included in future studies. Second, there was no information about TSH, fT4, and fT3 in the KNHANES from 2016 to 2018. Therefore, thyroid hormones could not be measured. However, we could provide exact measurements as we used the KNHANES questionnaires for information concerning physi-cian diagnosis and the prevalence of thyroid disease. Third, hyperthy-roidism, hypothyroidism, thyroid positive nodules and Hashimoto thy-roiditis were included thyroid disease in KNHANES. This study was not investigated in detail, such as the relationship between hyperthyroidism and sleep duration.

CONCLUSIONS

In conclusion, sex differences showed a relationship between sleep du-ration and thyroid disease. We propose to add thyroid hormones in gen-eral health examination blood tests and include thyroid cancer in the national cancer examination for examination once every two years for men and women. Additional studies are needed to confirm the association of sleep duration and thyroid disease with sleep quality according to sex and analyses with other interesting variables.

Notes

No potential conflict of interest relevant to this article was reported.

References

1. St-Onge MP, Grandner MA, Brown D, Conroy MB, Jean-Louis G, Coonset M, et al. Sleep duration and quality: impact on lifestyle behav-iors and cardiometabolic health: a scientific statement from the Amer-ican Heart Association. Circulation 2016;134(18):e367–e386. DOI: 10.1161/CIR.0000000000000444.
2. Czeisler CA. Impact of sleepiness and sleep deficiency on public health— utility of biomarkers. J Clin Sleep Med 2011;7(5 Suppl):S6–S8. DOI: 10.5664/JCSM.1340.
3. Keilani M, Crevenna R, Dorner TE. Sleep quality in subjects suffering from chronic pain. Wien Klin Wochenschr 2018;130(1-2):31–36. DOI: 10.1007/s00508-017-1256-1.
4. Kripke DF, Garfinkel L, Wingard DL, Klauber MR, Marleret MR. Mor-tality associated with sleep duration and insomnia. Arch Gen Psychia-try 2002;59(2):131–136. DOI: 10.1001/archpsyc.59.2.131.
5. Kim CE, Shin S, Lee HW, Lim J, Lee JK, Shin A, et al. Association be-tween sleep duration and metabolic syndrome: a cross-sectional study. BMC Public Health 2018;18(1):720. DOI: 10.1186/s12889-018-5557-8.
6. Merrill SJ, Mu Y. Thyroid autoimmunity as a window to autoimmunity: an explanation for sex differences in the prevalence of thyroid autoim-munity. J Theor Biol 2015;375:95–100. DOI: 10.1016/j.jtbi.2014.12.015.
7. Kim WG, Kim WB, Woo G, Kim H, Cho Y, Kim TY, et al. Thyroid stimulating hormone reference range and prevalence of thyroid dysfunction in the Korean population: Korea National Health and Nutrition Examination Survey 2013 to 2015. Endocrinol Metab (Seoul) 2017;32(1):106–114. DOI: 10.3803/EnM.2017.32.1.106.
8. Kim W, Lee J, Ha J, Jo K, Lim DJ, Lee JM, et al. Association between sleep duration and subclinical thyroid dysfunction based on nationally representative data. J Clin Med 2019;8(11):2010. DOI: 10.3390/jcm-8112010.
9. Schmid SM, Hallschmid M, Jauch-Chara K, Kück MC, Lehnert H, Schultes B. Partial sleep restriction modulates secretory activity of thy-rotropic axis in healthy men. J Sleep Res 2013;22(2):166–169. DOI: 10.1111/jsr.12004.
10. Kim Y. The Korea National Health and Nutrition Examination Survey (KNHANES): current status and challenges. Epidemiol Health 2014;36:e2014002. DOI: 10.4178/epih/e2014002.
11. Lee DH, Nam JY, Kwon S, Keum N, Lee JT, Shin MJ, et al. Lifestyle risk score and mortality in Korean adults: a population-based cohort study. Sci Rep 2020;10(1):10260. DOI: 10.1038/s41598-020-66742-y.
12. Song JE, Kim JM, Lee MY, Jang HJ, Park KH. Effects of consumption of alcohol on intraocular pressure: Korea National Health and Nutrition Examination Survey 2010 to 2011. Nutrients 2020;12(8):2420. DOI: 10.3390/nu12082420.
13. Han DH, Khang YH, Jung-Choi K, Lim S. Association between shift work and periodontal health in a representative sample of an Asian population. Scand J Work Environment & health 2013;:559–567.
14. Jeon J, Lee W, Choi WJ, Ham S, Kang SK. Association between working hours and self-rated health. Int J Environ Res Public Health 2020;17(8):2736. DOI: 10.3390/ijerph17082736.
15. Craig CL, Marshall AL, Sjöström M, Bauman AE, Booth ML, Ainsworth BE, et al. International physical activity questionnaire: 12-country reli-ability and validity. Med Sci Sports Exerc 2003;35(8):1381–1395. DOI: 10.1249/01.MSS.0000078924.61453.FB.
16. Yu J, Rawtaer I, Fam J, Jiang MJ, Feng L, Kua EH, et al. Sleep correlates of depression and anxiety in an elderly Asian population. Psychogeri-atrics 2016;16(3):191–195. DOI: 10.1111/psyg.12138.
17. Kurina LM, McClintock MK, Chen JH, Waite LJ, Thisted RA, Lauder-dale DS. Sleep duration and all-cause mortality: a critical review of measurement and associations. Ann Epidemiol 2013;23(6):361–370. DOI: 10.1016/j.annepidem.2013.03.015.
18. Roelfsema F, Pereira AM, Veldhuis JD, Adriaanse R, Endert E, Fliers E, et al. Thyrotropin secretion profiles are not different in men and wom-en. J Clin Endocrinol Metab 2009;94(10):3964–3967. DOI: 10.1210/jc.2009-1155.
19. Roelfsema F, Boelen A, Kalsbeek A, Fliers E. Regulatory aspects of the human hypothalamus-pituitary-thyroid axis. Best Pract Res Clin En-docrinol Metab 2017;31(5):487–503. DOI: 10.1016/j.beem.2017.09.004.
20. Kessler L, Nedeltcheva A, Imperial J, Penevet PD. Changes in serum TSH and free T4 during human sleep restriction. Sleep 2010;33(8):1115–1118. DOI: 10.1093/sleep/33.8.1115.
21. La J, Wang TS, Hammad AY, Burgardt L, Doffek K, Carr AA, Shaker JL, et al. Parathyroidectomy for primary hyperparathyroidism improves sleep quality: a prospective study. Surgery 2017;161(1):25–34. DOI: 10. 1016/j.surg.2016.05.047.
22. He Y, Meng Z, Jia Q, Hu F, He X, Tan J, et al. Sleep quality of patients with differentiated thyroid cancer. PLoS One 2015;10(6):e0130634. DOI: 10.1371/journal.pone.0130634.
23. Song L, Lei J, Jiang K, Lei Y, Tang Y, Zhu J, et al. The association between subclinical hypothyroidism and sleep quality: a population-based study. Risk Manag Healthc Policy 2019;12:369–374. DOI: 10.2147/RMHP. S234552.
24. Lou X, Wang H, Tu Y, Tan W, Jiang C, Sun J, et al. Alterations of sleep quality and circadian rhythm genes expression in elderly thyroid nod-ule patients and risks associated with thyroid malignancy. Sci Rep 2021;11(1):13682. DOI: 10.1038/s41598-021-93106-x.

Article information Continued

Table 1.

General characteristics of study population in the Korea National Health and Nutrition Examination Surveys 2016-2018

Variables Prevalence of thyroid disease p-value
Total No Yes
n % n % n %
Sleep duration (h)             0.630
 Insufficient (<7) 5,423 30.9 5,200 95.9 223 4.1  
 Normal (7-8) 8,116 46.2 7,807 96.2 309 3.8  
 Prolonged (≥9) 4,016 22.9 3,863 96.2 153 3.8  
Sex             <0.000
 Men 7,641 43.5 7,531 98.6 110 1.4  
 Women 9,914 56.5 9,339 94.2 575 5.8  
Age (y)             <0.000
 19-29 2,121 12.0 2,093 98.7 28 1.3  
 30-39 2,770 15.8 2,681 96.8 89 3.2  
 40-49 3,223 18.4 3,101 96.2 122 3.8  
 50-59 3,339 19.0 3,150 94.3 189 5.7  
 ≥60 6,102 34.8 5,845 95.8 257 4.2  
Household income             0.152
 Lowest 3,365 19.2 3,241 96.3 124 3.7  
 Low-moderate 4,247 24.3 4,068 95.8 179 4.2  
 Moderate-high 4,803 27.4 4,637 96.5 166 3.5  
 Highest 5,094 29.1 4,880 95.8 214 4.2  
 Missing 46            
Education             0.206
 Elementary school 3,626 20.7 3,474 95.8 152 4.2  
 Middle school 1,778 10.1 1,698 95.5 80 4.5  
 High school 5,609 32.0 5,389 96.1 220 3.9  
 ≥College 6,521 37.2 6,289 96.4 232 3.6  
 Missing 21            
Marital status             <0.000
 Married 14,600 83.2 13,963 95.6 637 4.4  
 Unmarried 2,955 16.8 2,907 98.4 48 1.6  
Current smoking             <0.000
 No 14,363 82.0 13,748 95.7 615 4.3  
 Yes 3,148 18.0 3,080 97.8 68 2.2  
 Missing              
High-risk alcohol consumption             0.000
 No 15,490 88.4 14,857 95.9 633 4.1  
 Yes 2,024 11.6 1,975 97.6 49 2.4  
 Missing 41            
Body mass index             0.080
 Underweight 654 3.7 638 97.6 16 2.5  
 Normal 10,738 61.4 10,299 95.9 439 4.1  
 Obesity 6,104 35.0 5,875 96.3 229 3.8  
 Missing 59            
Working hours per week             <0.000
 Not working 5,491 31.3 5,203 94.8 288 5.2  
 <20 1,674 9.5 1,610 96.2 64 3.8  
 20-39 2,910 16.6 2,805 96.4 105 3.6  
 40-59 6,043 34.4 5,865 97.1 178 3.0  
 ≥60 6,928 39.5 6,590 95.1 338 4.9  
 Missing 25            
Physical activity             0.691
 No 9,968 56.9 9,573 96.0 395 4.0  
 Yes 7,542 43.1 7,252 96.2 290 4.0  
 Missing 45            
Total 17,555 100.0 16,870 96.1 685 3.9  

Table 2.

The association between general characteristic and prevalence of thyroid disease among Korean adults in the Korean National Health and Nutrition Examination Surveys 2016-2018

Variables Prevalence of thyroid disease
OR 95% CI p-value
Sleep duration (h)        
 Insufficient (<7) 1.00 0.84 1.20 0.804
 Normal (7-8)   Reference  
 Prolonged (≥9) 1.05 0.86 1.29 0.605
Sex        
 Men   Reference  
 Women 4.52 3.56 5.73 <0.000
Age (y)        
 19-29   Reference  
 30-39 2.08 1.24 3.49 0.339
 40-49 2.43 1.44 4.11 0.585
 50-59 3.88 2.29 6.58 <0.000
 ≥60 3.30 1.91 5.70 0.001
Household income        
 Lowest   Reference  
 Low-moderate 1.21 0.94 1.55 0.221
 Moderate-high 1.02 0.78 1.33 0.245
 Highest 1.23 0.94 1.61 0.153
Education        
 Elementary school   Reference  
 Middle school 1.24 0.92 1.65 0.820
 High school 1.40 1.07 1.82 0.153
 ≥College 1.47 1.10 1.97 0.062
Marital status        
 Married 1.19 0.80 1.77 0.402
 Unmarried   Reference  
Current smoking        
 No   Reference  
 Yes 1.15 0.86 1.54 0.342
High-risk alcohol consumption        
 No   Reference  
 Yes 1.00 0.73 1.38 0.986
Body mass index        
 Underweight 0.64 0.38 1.07 0.078
 Normal   Reference  
 Obesity 1.02 0.86 1.21 0.098
Working hours per week        
 Not working 1.26 1.02 1.56 0.334
 <20 1.05 0.77 1.42 0.062
 20-39 0.94 0.73 1.21 0.007
 40-59   Reference  
 ≥60 1.19 0.85 1.66 0.281
Physical activity        
 No 0.92 0.78 1.08 0.281
 Yes   Reference  

OR, Odds ratio; CI, confidence interval.

Adjusted for sex, age, household income, education, marital status, current smoking, high-risk alcohol consumption, body mass index, working hours, physical activity, and sleep duration.

Figure 1.

The sex difference in the association between sleep duration and prevalence of thyroid disease among South Korean adults. Results are demonstrated odds ratios and 95% confidence intervals. Adjusted for age, household income, education, marital status, current smoking, high-risk alcohol consumption, body mass index, working hours, physical activity, and sleep duration.