Association between relative handgrip strength and glycemic control among male automobile manufacturing workers using vibration tools in South Korea

Background: Although the association between handgrip strength and glycemic control has been reported, studies conducted exclusively within specific occupational groups remain limited. To explore the association between handgrip strength and metabolic health in industrial settings, this study examined the relationship between relative handgrip strength and glycated hemoglobin (HbA1c) among male automobile manufacturing workers using vibration tools in South Korea.Methods: Using 66,212 occupational health examination records collected at Inha University Hospital between January 2024 and April 2025, a total of 3,365 workers with HbA1c and handgrip strength measurements were identified. After excluding duplicates (n = 1,536), female workers (n = 2), and records without Hb and estimated glomerular filtration rate, 1,823 male participants were included in the final analysis. Relative handgrip strength was calculated as the maximum value of bilateral grip strength divided by body mass index. Multiple linear regression analyses were conducted to assess the association between relative handgrip strength and HbA1c, adjusting for age, smoking status, alcohol consumption, current hypertension, current dyslipidemia, current hypoglycemic-agents use, family diabetes history, leisure-time physical activity, and resistance exercise.Results: Relative handgrip strength was inversely associated with HbA1c levels (B: –0.060; 95% confidence interval CI: −0.081 to −0.039; p < 0.001). The association was strongest among normoglycemic participants (B: −0.185; 95% CI: −0.305 to −0.065; p = 0.003). Effect size was reduced but significantly associated among individuals with prediabetes (B: −0.115; 95% CI: −0.180 to −0.050; p < 0.001) and further attenuated to a borderline significance in individuals with diabetes (B: −0.023; 95% CI: −0.050 to 0.003; p = 0.082). These findings indicate that greater muscle strength relative to body size is related to better glycemic control.Conclusions: Handgrip strength was associated with HbA1c levels in industrial workers. This study suggests that handgrip strength may provide complementary information on metabolic health in occupational settings.