Comorbidities	Randomized controlled trials	Observational studies	Retrospective, insurance database studies	Registries	Mixed methods
Prevalence (%)
Previous spine surgery	-	9.0 - 25.0 [24,40,46,75,87]	4.9 - 6.8 [8,36,102]	17.0 - 19.4 [23,47,92,93]	6.6 - 22.6 [22,45]
Symptom duration, years: mean (SD)/median [IQR]	-	15.8 (13.9) [43]	1.4, [103] 1.6 (1.7) [77]	-	3.3 [106]
	-	1 (0.8) [49]	11.2 [55]	-	7 [22]
	-	1.3 [75]	-	-	-
	-	2.1 [0-42], 1.9 [0-13]a[24]	-	-	-
Specified symptom duration, n (%)	105 (26.3)b[51]	182 (60.7),c[46] 194 (87.4)d[82]	-	3983 (52.1)e, 3009 (39.4)f[47]	-
Obesity (BMI>30)	41.2 - 43.6 [41,68]	15.8 -54.9 [24,40,46,84,89]	7.0 - 49.8 [54,55,57,80,101]	23.0 [92]	-
Hypertension	43.6 - 45.9 [41,59,[69], [70], [71]]	-	7.8 - 71.6 [56,61,78,80,98,103,105]	-	-
Diabetes	7.8 - 22.5 [41,51,59,[67], [68], [69], [70], [71]]	10.8 - 14.5 [40,53,82]	4.2 - 37.1 [[54], [55], [56],60,61,77,78,80,98,101,103,105]	-	3.0 - 14.4 [22,45,106]
Smoking	7.5 - 14.3 [41,51,59,67,[69], [70], [71]]	7.0 - 24.7 [24,40,43,46,48,49,82,94]	8.1 - 61.6 [54,77,80]	11.7 - 24.3 [42,44,47,92,93]	16.2 [106]
Cardiovascular disease
All, not specified	-	59.9 [27]	43.1 [61]	-	6.6 [22]
Arrhythmia	-	-	3.3 – 4.2 [56,103]	-	-
Coronary artery disease (CAD)	-	5.7 - 7.3 [53,83]	7.1 – 23.6 [54,56,103,105]	-	-
Heart failure	-	5.0 - 6.0 [53,83]	2.1 - 10.3 [54,60,103]	-	-
CAD/heart failure	-	6.3 [46]	-	-	-
CAD/heart disease	-	-	17.8 [78]	-	-
Heart disease	19.6 - 26.3 [41,59,[69], [70], [71]]	-	4.8 [80]	4.4 [42]	-