Effects of vitamin D supplementation on glycated haemoglobin and fasting glucose levels in hypertensive patients: a randomized controlled trial

AIM

To investigate the efficacy of vitamin D supplementation on glycaemic control.

METHODS

The Styrian Vitamin D Hypertension Trial was a single-centre, double-blind, placebo-controlled study conducted between 2011 and 2014 at the Medical University of Graz, Austria. We enrolled 200 people with arterial hypertension and 25-hydroxyvitamin D [25(OH)D] concentrations <30 ng/mL. Study participants were randomized to receive either 2800 IU of vitamin D or placebo per day for 8 weeks. The present study was a post hoc analysis that incorporated an analysis of covariance (ancova) approach, while adjusting for baseline differences.

RESULTS

A total of 185 participants [mean ± standard deviation age, 60.1 ± 11.3 years; 47% women; mean 25(OH)D 21.2 ± 5.6 ng/mL, mean glycated haemoglobin (HbA1c) 44.8 ± 11.8 mmol/mol and mean body mass index 30.4 ± 5.4 kg/m(2) ] completed the trial. ancova showed a mean treatment effect [95% confidence interval (CI)] on HbA1c of -3.52 (-6.7 to -0.34) mmol/mol (p = .045). There was no difference in fasting glucose -4.7 mg/dL (95% CI -16.3 to 6.9; p = .426).

CONCLUSIONS

Vitamin D supplementation in obese hypertensive patients with low 25(OH)D reduces HbA1c levels. This finding warrants further investigation into potential vitamin D effects on glucose homeostasis.

Resting heart rate and the risk of type 2 diabetes: A systematic review and dose--response meta-analysis of cohort studies

BACKGROUND

High resting heart rate has been associated with increased risk of type 2 diabetes in several studies, but the available data are not consistent and it is unclear if there is a dose-response relationship between resting heart rate and type 2 diabetes risk. We aimed to clarify this association by conducting a systematic review and meta-analysis of published studies.

METHODS AND RESULTS

PubMed, Embase and Ovid Medline databases were searched for prospective studies published up until October 11th, 2013. Summary relative risks were estimated using a random effects model. Ten cohort studies with >5628 cases and 119,915 participants were included. The summary RR for high vs. low resting heart rate was 1.83 (95% CI: 1.28-2.60, I(2) = 88%, n = 7), and in the dose-response analysis the summary RR was 1.20 (95% CI: 1.07-1.34, I(2) = 93%, n = 9) for an increase of 10 beats per minute. The heterogeneity was to a large degree explained by two studies. There was evidence of nonlinear associations between resting heart rate (pnonlinearity < 0.0001) and risk of type 2 diabetes.

CONCLUSION

The current meta-analysis indicates a strong positive association between high resting heart rate and the risk of type 2 diabetes. As a non-invasive marker of type 2 diabetes risk, resting heart rate may have potential in the clinical setting, especially for interventions aimed at lowering the risk of type 2 diabetes. Additional studies are needed to clarify the mechanisms that may be responsible for the assoiation between resting heart rate and type 2 diabetes.