The independent association of other factors with DM risk in the expected directions validate the assessment of DM and HbA1c: age (OR = 1.05, 95% CI: 1.04–1.08), being male (OR = 1.42, 95% CI: 0.89–2.00), highest socio-economic status (OR = 1.70, 95% CI: 1.08–2.67), ever smoker (OR = 1.89, 95% CI: 1.22–2.92), and exhibiting high Hb concentration (OR = 1.02, 95% CI: 1.15–1.25), and high BMI (OR = 1.20, 95% CI: 1.15–1.25). This evidence concerns the gene GSTM1 and diabetes mellitus.