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Background: Previous studies have reported an association between sarcopenia and type 2 diabetes mellitus (T2DM), but causation was prone to confounding factors. A more robust research approach is urgently required to investigate the causal relationship between sarcopenia and T2DM. Methods: The bi-directional two-sample MR study was carried out in two stages: Sarcopenia-related traits were investigated as exposure while T2DM was investigated as an outcome in the first step, whereas the second step was reversed. The GWAS summary data for hand-grip strength (n = 256,523), appendicular lean mass (ALM, n = 450,243), and walking pace (n = 459,915) were obtained from the UK Biobank. T2DM data were obtained from one of the biggest case-control studies on diabetes (DIAGRAM; n = 180,834 cases and 492,191 controls), which was published in 2022. The inverse-variance weighted (IVW) approach was used to obtain MR estimates, and various sensitivity analysis was also performed. Results: Low hand-grip strength had a potential causal relationship with an increased incidence of T2DM (OR = 1.109; 95% CI, 1.008-1.222; p = 0.0350). T2DM risk was reduced by increasing ALM and walking pace: A 1 kg/m² increase in ALM decreased the risk of T2DM by 10.2% (OR = 0.898; 95% CI, 0.830-0.952; p < 0.001). A1 m/s increase in walking pace decreased the risk of T2DM by 90.0% (OR = 0.100; 95% CI, 0.053-0.186; p < 0.001). The relationship was bidirectional, with T2DM as a causative factor of sarcopenia-related traits (p < 0.05) except for ALM (β = 0.018; 95% CI, -0.008 to -0.044; p = 0.168). Conclusions: Hand-grip strength and T2DM had a potential bidirectional causal relationship, as did walking pace and T2DM. We suggest that sarcopenia and T2DM may mutually have a significant causal effect on each other. [ABSTRACT FROM AUTHOR]

Objective: To provide an example of a new methodology for using multiple characteristics in the study of population aging and to assess its usefulness. Method: Using the English Longitudinal Study of Aging (ELSA), we investigate three characteristics of each person 60 to 85 years old, by level of education, hand-grip strength in 2004 (measured in kilos), chair rise speed in 2004 (measured in rises per minute), and whether the person survived from 2004 to 2012. Because the three characteristics are measured in different units, we convert them into a common metric, called alpha-ages. Results: We find that the average of the alpha-age differentials in the measures of upper body and lower body strength predicts educational differentials in subsequent survival better than either physical measure alone. Discussion: This result demonstrates the benefit of combining characteristics, using alpha-ages to convert incommensurate observations into a common metric. [ABSTRACT FROM AUTHOR]