Table 3. Hazard ratio and 95% confidence intervals of heart diseases according to the subgroup analysis.

Subgroup analysis was performed according to disease severity and duration.

		Univariate			Adjusted*
	Event/total	HR (95% CI)		P-value	HR (95% CI)		P-value
By disease severity
Control subjects	375/18850	1.00	(reference)		1.00	(reference)
Mild AA patients	89/3664	1.27	(0.97–1.53)	0.096	1.21	(0.96–1.52)	0.110
Severe AA patients	0/106	NA	NA	NA	NA	NA	NA
By disease duration
Control subjects	375/18850	1.00	(reference)		1.00	(reference)
Episodic AA patients	80/3342	1.23	(0.96–1.56)	0.099	1.22	(0.96–1.55)	0.113
Long-standing AA patients	9/419	0.90	(0.46–1.74)	0.746	0.89	(0.46–1.73)	0.738

AA, alopecia areata; CI, confidence interval; NA, not applicable

*Adjusted for the variables of significant difference in frequency by Chi square test.