Table 2.

Summary of the studies analyzing the prevalence of CA in Episodic Migraine (EM) vs. Chronic Migraine (CM) (in %) and those identifying CA as a risk factor for migraine chronification (NA, Not Applicable; TTH, Tension Type Headache; HTTH, Chronic Tension Type Headache).

References	Year	Number of patients	Country	CA as a risk factor for chronification	Type of migraine	CA prevalence in EM %	CA prevalence in CM %
Russo et al. (55)	2020	50	Italy	YES	Migraine	NA	NA
Mathew et al. (19)	2016	44	U.S.	YES	CM	–	~90%
Louter et al. (26)	2013	3,029	Netherlands	YES	Migraine	–	–
Tietjen et al. (34)	2009	1,413	U.S.	NA	Migraine	–	–