Temporal changes in the epidemiology of diabetes mellitus in Turkey: A systematic review and meta-analysis

OBJECTIVE
Diabetes mellitus (DM) is a serious public health problem. Despite various epidemiological studies reporting prevalence of DM in Turkey, there is no meta-analysis or systematic review evaluating these studies as a whole and assessing temporal changes in the prevalence of DM. In this meta-analysis, the studies that have been conducted in the last 15 years and which provide information on the prevalence of DM in our country are examined.

METHODS
Epidemiological studies on cardiovascular risk factors in adult Turkish population that had been conducted within the last 15 years and having the capacity of either representating or potentially representing the country, were searched through Ovid, Medline and Web of Science Core Collection the Turkish Academic Network and Information Center (ULAKBIM) databases. Additionally, websites of Ministry of Health and related societies were investigated for additional studies. Random effects model was used in meta-analysis of low bias risk studies. Meta-regression was performed to evaluate the temporal change in DM prevalence.

RESULTS
There were 8 studies which provided information with regard to DM prevalence (n=84656). Four of these studies (n=56853) had low bias risk and four had high bias risk (n=27803). When compared with low bias risk studies, those with high bias risk had very large variation of DM prevalence (between 4% to 15%). Meta-analysis of the low bias risk group yielded a crude DM prevalence of 13.5% (95% CI: 11.6-15.5%) in the whole group, 14.2% (95% CI: 12.3-16.2%) in females, 12.6% (95% CI: 10.5-14.9%) in males. In meta-regression analysis of low bias risk group, mean age difference among the studies and the time period in which the study was undertaken were partially able to explain the inter-study heterogeneity (R2 values were 52% and 78%).

CONCLUSION
This meta-analysis shows that DM is a highly prevalent public health problem in our country. Contrary to studies, which compare the recent studies with previous ones and report an increasing prevalence of DM, the present meta-analysis–despite its limitations-provides findings that the temporal increase of DM prevalence is at least paused over time. This situation underlines the need for new studies.