Sarcopenia: a potential cause and consequence of type 2 diabetes in Australia's ageing population?

Letter to the Editor: We read with interest the excellent review by Scott and colleagues on the contribution of sarcopenia to type 2 diabetes in the ageing Australian population. In a prospective Australian cohort of community‐dwelling men, we recently found that muscle grip strength and muscle quality, but not muscle mass, were associated with incident type 2 diabetes at 5 years follow‐up. These associations were not mediated by serum interleukin 6 or tumour necrosis alpha.As we did not examine sarcopenia, nor appendicular lean mass adjusted for body mass index (ALM‐BMI), we have undertaken further analysis in 1180 participants with valid sarcopenia data. Their mean age was 56.9 years (standard deviation [SD] ± 10.9), mean ALM‐BMI at baseline was 0.950 (SD ± 0.135) and mean peak hand grip strength at baseline was 48.7 kg (SD ± 9.9 kg). At 5 years follow‐up, incident type 2 diabetes occurred in 119 participants (10.1%).Baseline ALM‐BMI of less than 0.789 occurred in 9.2% of patients (n = 109) and baseline grip strength of less than 26 kg occurred in 1.4% of patients (n = 16), thus only six participants (0.5%) had sarcopenia as defined by the Foundation for the National Institutes of Health Biomarkers Consortium Sarcopenia Project (both ALM‐BMI < 0.789 and peak hand grip strength < 26 kg). Hence, in our middle‐aged Australian cohort of men, the prevalence of sarcopenia was very low. Moreover, while there was an unadjusted association between baseline ALM‐BMI of less than 0.789 and incident type 2 diabetes (odds ratio [OR] 2.54; 95% CI, 1.49–4.17; P < 0.001), this attenuated to non‐significance after adjustment for age, subcohort, income, fasting plasma glucose, physical activity, family history of diabetes, triglycerides and hypertension (OR 1.73; 95% CI, 0.95–3.05; P = 0.06). However, when analysing ALM‐BMI as a continuous variable, the adjusted association was significant (OR per 0.1 unit decrease: 1.33; 95% CI, 1.13–1.58; P < 0.001). Overt sarcopenia may not have a large contribution to type 2 diabetes in community‐dwelling Australians. Rather, reduction of skeletal muscle strength, ALM‐BMI and muscle quality across the spectrum of healthy values may have greater population level significance. Our previous population‐attributable fraction calculations suggest that a substantial proportion of incident type 2 diabetes may be prevented if muscle strength in the Australian community was generally increased.