Meta-analysis of Serum Vitamin B12 Levels and Diabetic Retinopathy in Type 2 Diabetes

BACKGROUND

Previous studies have shown an association between low serum vitamin B12 levels and the risk of diabetic retinopathy (DR) in type 2 diabetes, but the conclusions from various studies were inconsistent. Therefore, we collected relevant data from various databases to perform a meta-analysis and address the inconsistencies in these studies.

METHODS

We searched PubMed, Embase, Cochrane Library, CNKI, Wanfang and CQVIP for eligible studies published up to April 10, 2022, and performed a meta-analysis using Stata software to assess the association between serum vitamin B12 levels and DR.

RESULTS

A total of 15 studies were included in this meta-analysis. Statistical analysis showed that serum vitamin B12 levels were significantly reduced in patients with type 2 diabetic retinopathy ,WMD 95% CI = -68.91 (-76.76, -61.06) (p <0.00001, I² = 88.30%). In subgroup analyses by ethnicity, an association between low serum vitamin B12 levels and DR risk was found in East Asian, South Asian and mixed populations, but not in Caucasian populations.

CONCLUSIONS

This meta-analysis analyzed vitamin B12 in patients with type 2 diabetic retinopathy and emphasized the importance of monitoring serum vitamin B12 levels in patients with type 2 diabetic retinopathy, but this meta-analysis still has deficiencies and limitations, and more clinical studies are needed to confirm this conclusion in the future.

Active smoking among people with diabetes mellitus or hypertension in Africa: a systematic review and meta-analysis

The objective was to summarize existing data on the prevalence of active tobacco smoking among patients with hypertension or diabetes mellitus in Africa. We searched PubMed, EMBASE, and AJOL to include studies published from January 01, 2000 to August 23, 2017 reporting on the prevalence of active smoking in individuals aged ≥15 years with hypertension or diabetes mellitus residing inside Africa. We used a random-effects meta-analysis model to pool studies. The pooled prevalence of active smoking among patients with hypertension or diabetes was 12.9% (95%CI: 10.6–15.3; 50 studies; 16,980 patients) and 12.9% (95%CI: 9.6–16.6; 42 studies; 18,564 patients), respectively. For both conditions, the prevalence of active smoking was higher in males than in females (p < 0.001), and in Northern compared to sub-Saharan Africa (p < 0.001). There was no difference between urban and rural settings, and between community-based and hospital-based studies, except for patients with diabetes for whom the prevalence was higher in hospital-based studies (p = 0.032). The prevalence of active smoking is high among patients with hypertension or diabetes mellitus in Africa, with the heaviest burden in Northern Africa. Interventions for smoking prevention or cessation should be implemented in these high risk populations, targeting particularly the males.