XXXX and mortality: a systematic review of observational studies.

@entity1 @entity649 @entity2489 @entity130
OBJECTIVE: To determine the attributable mortality of @entity2489 in a systematic review and meta-analysis of observational studies. @entity2489 is generally believed to increase the mortality of @entity1 . This notion is predominantly based on the results of observational studies. DATA SOURCE: We performed a systematic search strategy using PubMed, Web of Science, and Embase from their inception through February 2007. In addition, a reference and related article search was performed. STUDY SELECTION: Studies were included if they reported mortality rates of @entity1 with and without @entity2489 . DATA EXTRACTION AND SYNTHESIS: Fifty-two studies with a total of 17,347 @entity1 met the inclusion criteria. Pooling of all studies resulted in relative risk of 1.27 (95% Confidence Interval = 1.15-1.39), but heterogeneity was considerable (I2 statistic = 69%). The origin of heterogeneity could not be explained by differences in study design, study quality, and diagnostic approach. However, heterogeneity was limited for studies investigating only @entity130 @entity1 (I2 = 1.3%) or @entity1 with acute @entity649 (I2 = 0%), with estimated relative risk of 1.09 (95% Confidence Interval = 0.87-1.37) among @entity130 @entity1 and 0.86 (95% Confidence Interval = 0.72-1.04) among @entity1 with acute @entity649 . CONCLUSIONS: There is no evidence of attributable mortality due to @entity2489 in @entity1 with @entity130 or acute @entity649 . However, in other nonspecified @entity1 groups, there is evidence for attributable mortality due to @entity2489 , but this could not be quantified due to heterogeneity in study results. More detailed studies, allowing subgroup analyses, are needed to determine the attributable mortality of @entity2489 in these @entity1 populations.
