carcinoma [41], and so on. Our meta-analysis has obtained
consistent results with these studies.
Our study has some limitations. First, as a meta-analysis of
observational studies, we cannot rule out that individual studies
may have failed to control for potential confounders, which may
introduce bias in an unpredictable direction. Second, the association
was only significant in case–control studies but not in
cohort studies. Most studies included in this meta-analysis were
case–control studies. Overstated association may be expected
from the case–control studies because of recall or selection bias,
and early symptoms in patients may have resulted in a change in
dietary habits. Thus, further cohort studies are warranted to
confirm the results. Third, measurement errors are important in
the assessment of meat consumption, which can lead to overestimation
of the range of consumption and underestimation of
the magnitude of the relationship between meat consumption
and cancer risk [42]. Fourth, between-study heterogeneity was
found in some subgroup analysis in this meta-analysis, but the
between-study heterogeneity was not successfully explained by
meta-regression. However, other genetic and environment variables
may well be potential contributors to this disease–effect
unconformity. In this respect, the lack of relevant study-level
covariates in the reported articles precluded a more robust
assessment of sources of this heterogeneity. Fifth, we may not
have found a significant association between red meat consumption
and risk for glioma because a limited number of
studies were included. Further studies should be conducted to
assess the association between red meat and glioma risk. Finally,
publication bias could be of concern in meta-analysis because of
the small number of studies included [32,33]. Nevertheless, we
found no evidence of publication bias.