First, known, unknown and/or unrecognized differences between study settings may obstruct generalizability of results.
There were significant differences in the targeted risk factors between study settings: North American studies were more likely to evaluate the economics of interventions addressing smoking, dietary intake and dyslipidemia, while studies assessing interventions within a European context more often addressed high blood pressure and glucose levels.
The comparability between all these studies is limited by differences in the study settings and health care systems resulting in different ICU admission policies and practices.
Study settings and population The study was implemented in two different settings, rural and urban.
While between-survey similarities/differences in study settings, design and respondent characteristics might explain the observed differences and similarities, the trend observed in the present survey may be due to the involvement of senior residents in mandatory dissertation-related research.
Our study findings contradicted this, with increased odds of LTFU among patients with better immune system indicators (higher CD4 cell count and less advanced WHO stage), and this could be due to methodological differences with respect to operational definitions and also differences between the study settings.
Heterogeneity in the studies we reviewed may arise from inherent differences between the study settings, as well as from differences in study designs and analysis methods.
Noticeably, the effect estimates in this study are large compared with those of other studies, perhaps because of the different climatic conditions between different study settings.
It is possible that differences between the study settings such as screening procedures for GDM, or due to variations in the content of cigarettes [ 72] or in the frequency of stopping smoking during pregnancy may explain this inconsistency.
