Effects of telephone call intervention on cardiovascular risk factors in T2DM: A meta-analysis

Background: Mobile health interventions utilising telephone calls are promising tools for diabetes management. However, there is still a lack of convincing evidence demonstrating their beneficial effects on cardiovascular risk factors. The aim of this meta-analysis of randomised controlled trials was to assess the effect of telephone calls on glycaemic control and other cardiovascular risk factors in type 2 diabetes mellitus patients.

Methods: Two independent reviewers searched three online databases (PubMed, the Cochrane Library and EMBASE) to identify relevant English-language randomised controlled trials up to September 2017. Randomised controlled trials that assessed the effects of telephone calls on glycaemic control and other cardiovascular risk factors in type 2 diabetes mellitus patients were included. Effect size was calculated for changes in glycosylated haemoglobin A1c, weight, blood pressure and lipid levels using fixed- or random-effects models.

Results: Eighteen studies involving 3954 patients were included in the meta-analysis. Compared with usual care, telephone calls significantly decreased glycosylated haemoglobin A1c, by 0.12% (95% confidence interval: -0.22% to -0.02%). Univariate regression analysis showed that none of the covariates (number of participants, baseline age, baseline glycosylated haemoglobin A1c, duration of diabetes, call maker, number of calls and duration of study) had an impact on glycosylated haemoglobin A1c. For other cardiovascular risk factors, telephone calls significantly reduced systolic blood pressure by 0.19 mm Hg (95% confidence interval: -0.34% to -0.03%) but non-significantly changed diastolic blood pressure, body mass index, low-density lipoprotein cholesterol, total cholesterol, triglyceride or high-density cholesterol levels.

Conclusions: This meta-analysis supports the hypothesis that telephone calls offer moderate benefits for glycosylated haemoglobin A1c and systolic blood pressure reduction among type 2 diabetes mellitus patients. However, the data remain insufficient regarding the association of telephone calls with lowered diastolic blood pressure, body mass index or improved lipoprotein profiles.