Number of papers

Number of materials after duplication

Number of materials after review (based on the purpose of paper)

Number of materials after abstraction

Number of selected papers

PubMed

17

13

10

4

3

The Journal of frailty & aging

1

1

1

1

1

Elsevier

2

2

2

1

1

PMC

2

2

2

1

1

Medline

3

1

1

1

0

BMJ journals

2

2

1

1

1

Total

27

21

17

9

7