Gut microbiota changes associated with frailty in older adults: A systematic review of observational studies

Table 4 The Newcastle-Ottawa Scale assessment for the case-control study

Ref.	Selection				Comparability	Exposure			Scores
	Adequate definition of case	Representativeness of the case	Selection of controls	Definition of controls	Control for important factor	Ascertainment of exposure	Same method of ascertain for cases and controls	Non-responsese rate
Ticinesi et al[26], 2017	Yes	Yes	Yes	Yes	Yes	Yes, Yes		Yes	7

Yes is one point, the total number of stars represents a number of points.