Table 3. Joint effect between dry eye syndrome and comorbidity in association with chronic fatigue syndrome in study population.

Variables		N	Event	Adjusted HR (95% CI)	p for interaction
DES	Comorbidity‡				0.44
No	No	1699	17	1.00
No	Yes	1837	37	1.89 (1.05–3.39)*
Yes	No	258	3	1.18 (0.35–4.04)
Yes	Yes	626	25	3.77 (2.02–7.04)***

Abbreviation: DES, dry eye syndrome; HR, hazard ratio; CI, confidence interval.

Adjusted HR: adjusted for gender and age in multiple logistic regression models.

^‡ Patients with any one of cancers, systemic lupus erythematosus, rheumatoid arthritis, Sjogren syndrome, depression, anxiety, sleep disturbance, irritable bowel syndrome, and fibromyalgia were classified as the comorbidity group.

^* p < 0.05, ^*** p < 0.001.