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

We read with interest the excellent review by Scott and colleagues1 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.2 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).3 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.2