Patients with both high waist circumference and low grip strength had the highest risk for developing type 2 diabetes in a large prospective UK Biobank study, although researchers cautioned that the clinical utility of combining the measures for risk prediction remains uncertain.
In findings published in BMC Medicine, patients with high waist circumference and low grip strength had a hazard ratio of 7.68 for incident type 2 diabetes compared with those with low waist circumference and high grip strength. Researchers reported that abdominal adiposity remained the dominant factor associated with diabetes risk, while lower grip strength provided additional but more modest risk stratification.
Researchers analyzed data from 483,578 UK Biobank participants aged 40 to 69 years who did not have type 2 diabetes at baseline between 2006 and 2010. To reduce potential reverse causation, investigators excluded patients who developed type 2 diabetes within the first 2 years of follow-up. According to the researchers, this was the first prospective study in a large European cohort to jointly examine waist circumference and grip strength in relation to incident type 2 diabetes.
Waist circumference was measured using World Health Organization thresholds, and grip strength was assessed with a hydraulic dynamometer and categorized into age- and sex-specific tertiles. Incident type 2 diabetes was identified through linked hospital inpatient records using ICD diagnostic codes. Over 13 years of follow-up totaling approximately 6.3 million person-years, 30,240 patients developed type 2 diabetes.
In separate mutually adjusted analyses, intermediate waist circumference was associated with approximately double the hazard of developing type 2 diabetes compared with low waist circumference, while high waist circumference was associated with more than a fivefold higher hazard. By comparison, low grip strength was associated with a 35% higher hazard relative to high grip strength.
Joint analyses showed a graded increase in diabetes risk across the nine-waist circumference and grip strength combinations. Patients with intermediate waist circumference and low grip strength had an HR of 3.05, while those with high waist circumference and high grip strength had an HR of 5.98, both compared with patients with low waist circumference and high grip strength.
Sex-specific analyses showed stronger waist circumference associations among women and somewhat stronger grip strength associations among men. High vs low waist circumference was associated with an HR of 7.72 among women compared with 4.48 among men. Women with both high waist circumference and low grip strength had an HR of 10.24 for type 2 diabetes, whereas men with the same phenotype had an HR of 6.47.
Age-stratified analyses suggested stronger associations among younger patients. Patients younger than 60 years with high waist circumference and low grip strength had an HR of 10.12 for type 2 diabetes compared with an HR of 6.04 among those aged 60 years or older.
The researchers reported evidence of additive interaction between abdominal adiposity and lower grip strength, although the magnitude was modest. Overall, approximately 9% of the excess risk associated with the combined phenotype was attributable to the interaction itself beyond the sum of the individual effects. They also identified a sub multiplicative interaction, meaning that low grip strength contributed proportionally less additional relative risk among patients who already had high waist circumference than among leaner patients.
Additional analyses adjusting for physical activity, height, and family history of diabetes produced similar findings. Results also remained consistent when investigators applied alternative grip strength definitions and multiple imputation methods.
The researchers emphasized that grip strength should be interpreted primarily as a marker of overall muscular fitness, lean mass, and metabolic reserve rather than a direct causal determinant of diabetes risk. They also noted that the study did not evaluate whether adding grip strength measurements improves diabetes prediction beyond established clinical risk models.
Several limitations were noted, including single baseline measurements of waist circumference and grip strength, potential residual confounding, and the observational design, which precludes causal inference. The proportional hazards assumption also showed modest violations, meaning the hazard ratios should be interpreted as average associations across the follow-up period rather than fixed long-term risk estimates. Generalizability may be limited because UK Biobank participants tend to be healthier and less socioeconomically diverse than the broader population.
“The combination of high waist circumference and low grip strength conferred the greatest risk,” wrote lead study author Johanna Wirler, of the University of Regensburg in Germany, and colleagues. The researchers added that combined assessment of waist circumference and grip strength “may contribute to diabetes risk stratification,” although formal evaluation of incremental predictive utility is still needed.
Disclosures: The researchers reported no competing interests. Funding sources included the World Cancer Research Fund and the German Research Foundation.
Source: BMC Medicine
