Table 1.

Sample attrition table

Attrition criterion	N
Total number of de-identified patients in the Humedica database available for this research from January 1, 2011–December 31, 2012	9,318,581
Patients aged ≥18 years in 2011	7,696,733
And enrolled in integrated delivery network	4,192,869
And with ≥1 encounter with a health care provider in 2011 and 2012	720,912
Patients with cancer diagnosis (exclusion)	109,094
Patients with transplantation (exclusion)	5,163
Patients with nursing home (exclusion)	5,099
Patients with FM diagnosis prior to 2012 (exclusion)	20,026
Excluding patients with cancer diagnosis, transplantation, in nursing home, or FM diagnosis prior to 2012	132,574
Patients meeting all inclusion and exclusion criteria	588,338
Missing sex value	377
Total patients in analysis population	587,961
≥2 ICD-9 codes for FM (729.1) at least 30 days apart during 2012	4,296
Number of patients in no-FM cohort	583,665

Abbreviations: FM, fibromyalgia; ICD-9, International Classification of Diseases, Ninth Revision.