Hyperglycemia predicted persistently lower muscle strength in patients as they age, but peripheral neuropathy may partly account for the effects, according to research published in Diabetes Care.

“The relationship of hyperglycemia with longitudinal impairments in muscle function may represent an early stage in the development of disability, frailty and potentially early mortality in persons with diabetes,” Rita Rastogi Kalyani, MD, of Johns Hopkins University, told Endocrine Today. “Further research is needed in this area.”

Rita Rastogi Kalyani

Kalyani and colleagues evaluated 984 patients aged 25 to 96 years involved in the Baltimore Longitudinal Study of Aging (2003–2011).

Patients had HbA1c, knee extensor strength (isokinetic dynamometer) and lean body mass (DXA) measured at baseline and repeated measurements up to 7.5 years later. Muscle quality was defined as knee extensor strength/leg lean mass.

The researchers categorized participants by HbA1c quartile (<5.5%, 5.5%-5.79%, 5.8%-6.09% and ≥6.1% or <37, 37-40, 40-43 and ≥43 mmol/mol). Mixed-effects regression models were used to assess muscle outcomes in relation to HbA1c.

Across all HbA1c quartiles, muscle strength and quality were reduced (P<.001 for both), without differences in muscle mass at baseline.

Strength was significantly lower in the highest vs. lowest HbA1c quartiles (–4.7 ± 2.3 Nm; P value trend=.02), with adjustments for age, race, sex, weight and height. Results remained unchanged after adjusting for physical activity (P value trend=.045), but borderline significance was seen with additional adjustment for peripheral neuropathy (P value trend=.05).

Muscle quality also was lower in the highest vs. lowest HbA1c quartiles (–0.32 ± 0.15 Nm/kg; P value trend=.02), with adjustments for demographics. However, the differences diminished after adjusting for weight and height (–0.25 ± 0.15 Nm/kg; P value trend=.07). Measures of muscle mass were similar across all HbA1c quartiles.

“Further interventional studies are needed to better investigate if improving hyperglycemia and/or insulin resistance can impact loss of muscle strength over time and also to better understand mechanisms underlying the observed associations,” Kalyani said. — by Allegra Tiver