Efficacy and safety of Z-substances in the management of insomnia in older adults: a systematic review for the development of recommendations to reduce potentially inappropriate prescribing

Table 3 Risk of bias of case-control and case-crossover studies

Study	Clear focus of research	Appropriate method of measurement	Acceptable recruitment of cases	Acceptable selection of controls	Accurate measurement of exposure	Equal treatment of groups	Identification and consideration of confounding factors	Size of treatment effect	Precision of estimate	Believability of results	Local application	Confirms available research
Berry 2013	Yes	Yes	Yes	Unknown	Yes	Yes	Yes	OR 1.47	CI95* 1.24–1.74	Yes	Unknown	Yes
Chang 2011	Yes	Yes	Yes	No	Yes	Yes	No	OR 2.38	CI95 1.04–5.43	No	Unknown	Yes
Kang 2012	Yes	Yes	Yes	Unknown	Yes	Yes	Yes	OR 1.84	CI95 1.47–2.3	Yes	Unknown	Partially
Lai 2015	Yes	Yes	Yes	No	Yes	Yes	No	OR 3.87	CI95 2.71–5.53	No	Unknown	Yes
Pierfitte 2001	Yes	Yes	Yes	No	Yes	Yes	No	OR 1.3	CI95 0.7–2.5	Yes	Yes	Yes
Tang 2015	Yes	Yes	Yes	Unknown	Yes	Yes	Yes	OR 1.23	CI95 1.06–1.44	Yes	Unknown	Yes
Tom 2016	Yes	Yes	Yes	Unknown	Yes	Yes	Yes	OR 1.87	CI95 1.56–2.25	Yes	Unknown	Yes
Wang 2001	Yes	Yes	Yes	No	Yes	Yes	No	OR 2.26	CI95 1.28–3.97	No	Unknown	Yes
Zint 2010	Yes	Yes	Yes	No	Yes	Yes	No	RR 1.48	CI95 1.32–1.66	No	Yes	Yes

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