Supplementary Table 1.

Risk of bias in retrospective studies using modified Newcastle-Ottawa scale.

Study	Selection			Comparability	Outcome
	Representative treatment group	Representative control group	Ascertainment of diagnosis		Assessment of outcome	Adequate follow-up
Gao 2015	Yes	Yes	NIDDK*	Comparable for baseline symptom scores**, urinary frequency, age, and gender	Yes	Yes

^*NIDDK – National Institute of Diabetes and Digestive and Kidney Diseases;

^**Symptom scores included O’Leary-Saint score, the 0–10 Visual Analog Scale score, and quality of life score.