The Relationship Between Primary Sleep Disorders and Temporomandibular Disorders: An 8-Year Nationwide Cohort Study in South Korea

Figures & data

Figure 1 Flow chart of identifying the study population from the National Health Insurance Service-Health Screening Cohort database of the Republic of Korea.

Table 1 Demographic and Clinical Characteristics of the Study Population According to the Presence of Primary Sleep Disorders

	No Sleep Disorder	Sleep Disorder	P value
Number of subjects, n, (%)	461,883 (98.5)	6,999 (1.5)
Number of TMD cases, n, (%)	1,171 (97.3)	33 (2.7)
Incidence rate, (95% CI) *	3.3 (2.9–3.8)	6.1 (5.4–7.1)	< 0.001
Age, years, mean (SD)	55.4 (9.5)	61.0 (10.1)	< 0.001
Sex, %
Male	53.5	41.6	< 0.001
Female	46.5	58.4
Household income, quartile, %
1st (highest)	15.3	16.7	< 0.001
2nd	21.8	22.7
3rd	29.0	27.4
4th (lowest)	33.9	33.2
Smoking status, %
Never	69.5	77.1	< 0.001
< 10 years	3.9	2.9
10–29 years	7.2	4.3
≥ 30 years	19.4	15.7
Alcohol consumption, per week, %
Never	58.7	71.0	< 0.001
< 3 times	30.4	20.6
≥ 3 times	10.9	8.4
Physical exercise, per week, %
Never	54.1	58.5	< 0.001
< 3 times	24.7	18.4
≥ 3 times	21.2	23.1
Hypertension, %
No	70.0	67.0	< 0.001
Yes	30.0	33.0
Diabetes mellitus, %
No	92.0	91.0	< 0.001
Yes	8.0	9.0
Hyperlipidemia, %
No	53.4	50.7	< 0.001
Yes	46.6	49.3
BMI, %
< 25	65.3	65.8	0.315
≥ 25	34.7	34.2
CCI, %
0	14.5	3.3	< 0.001
1	21.7	8.6
2	20.8	13.7
≥ 3	43.0	74.4

Notes: Continuous variables are expressed as mean (SD), and categorical variables as %. Analysis of variance for continuous variables and Chi-square test for categorical variables. *per 10⁴ person-years.

Abbreviations: SD, standard deviation; BMI, body mass index; CCI, Charlson Comorbidity Index; TMD, temporomandibular disorders; CI, confidence interval.

Figure 2 Kaplan–Meier survival curve for log survival probability according to primary sleep disorder on new events of temporomandibular disorders over 8 years follow-up.

Table 2 Hazard Ratios for Temporomandibular Disorders According to the Presence of Primary Sleep Disorders

Temporomandibular Disorders	Presence of Sleep Disorder
	No	Yes
Model 1
aHR (95% CI)	1.00 (reference)	*1.55 (1.09–2.19)
Model 2
aHR (95% CI)	1.00 (reference)	*1.56 (1.10–2.20)
Model 3
aHR (95% CI)	1.00 (reference)	*1.56 (1.10–2.21)
Model 4
aHR (95% CI)	1.00 (reference)	*1.44 (1.02–2.04)

Notes: Model 1 was adjusted for age and sex; model 2 was adjusted for variables included in model 1 and household income; model 3 was adjusted for variables included in model 2 and smoking status, alcohol consumption, and physical exercise; model 4 was adjusted for variables included in model 3 and hypertension, diabetes mellitus, hyperlipidemia, body mass index, and Charlson comorbidity index. *P indicates a significant difference.

Abbreviations: aHR, adjusted hazard ratio; CI, confidence interval.

Figure 3 Subgroup analysis of the association between primary sleep disorders and temporomandibular disorders by sex (A), age (B), and physical exercise (C). Bold indicates P < 0.05.