Limitations
Several limitations should be addressed when interpreting our results. First, our analysis consists of observational, non-randomized studies, which have inherent flaws in terms of selection bias and unmeasured confounders. Second, the current meta-analysis is based on study-level data; lack of patient level data precludes further subgroup analysis. Third, the lack of clinical outcomes limits conclusions regarding the long-term implications of this association. Fourth, there was significant heterogeneity among studies for many end point definitions such as OSA definition, severity, echocardiographic definition of DD. Fifth, the number of studies examining the correlation between DD and severity of sleep apnea were limited therefore definitive conclusions with regards to the association between DD and OSA severity would be precarious. In spite these limitations, the results of the present study can be used to inform future studies.