Study by

Year

Number of patients

Hazard ratio

95% CI

Kwan et al. [78]

1997 - 2000

1945

0.67

0.39, 1.13

Ahern et al. [21]

1996 - 2003

18,769

0.7

0.57, 0.86

Chae et al. [20]

1999 - 2005

703

0.4

0.24, 0.67

Nickels et al. [79]

2001 - 2005

3024

0.83

0.54, 1.24

Boudreau et al. [80]

1990 - 2008

4216

0.82

0.62, 1.08