Ling classification describes endoscopic progressive process of achalasia and successful peroral endoscopy myotomy prevents endoscopic progression of achalasia

Table 2 Comparison of symptom duration, lower esophageal sphincter pressure, and dysphagia score among Ling classifications

Ling type	I	IIa	IIb	IIc	III	P value
n	119	106	60	60	14
Onset age (yr), mean	35.3	38.9	36.1	36.4	32.9	> 0.05
Age at time of diagnosis (yr), mean	38.5	42.8	43.8	46.4	45.4	< 0.05
Sex (female/male)	65/54	60/46	32/28	35/25	5/9	> 0.05
Duration (mo), median	24	36	60	72	120	< 0.05
LESP (mmHg), mean	35	34.7	32.8	28.9	16.9	< 0.05

LESP: Lower esophageal sphincter pressure.