Date Published: November 25, 2017
Publisher: Oxford University Press
Author(s): Antoneta Granic, Karen Davies, Carmen Martin-Ruiz, Carol Jagger, Thomas B L Kirkwood, Thomas von Zglinicki, Avan Aihie Sayer.
weak grip strength (GS) and chronic inflammation have been implicated in the aetiology of sarcopenia in older adults. Given the interrelationships between inflammatory biomarkers, a summary variable may provide better insight into the relationship between inflammation and muscle strength. This approach has not been investigated in very old adults (aged ≥85) who are at highest risk of muscle weakness.
we used mixed models to explore the prospective association between GS over 5 years in 845 participants in the Newcastle 85+ Study, and inflammatory components identified by principal component analysis (PCA). Cut-offs of ≤27 kg (men) and ≤16 (women) were used to define sub-cohorts with weak and normal GS at each assessment.
PCA identified three components, which explained 70% of the total variance in seven baseline biomarkers. Basal interleukin-6 (IL-6) and tumour necrosis factor (TNF-α) had the highest loadings on Component 1; stimulated IL-6 and TNF-α and homocysteine the highest on Component 2; high-sensitivity C-reactive protein (hsCRP) loaded positively and albumin negatively to Component 3. In adjusted mixed models, only Component 3 was associated with GS. One SD increase of Component 3 was associated with a 0.41 kg lower GS initially (P = 0.03) in all participants, but not with GS decline over time. Similar conclusions held for those in the weak and normal GS sub-cohorts.
an inflammatory profile including hsCRP and albumin was independently associated with baseline GS. Future studies linking inflammatory profiles and muscle strength are needed to corroborate these findings in older adults.
Weak grip strength (GS)—an indicator of upper-body and overall muscle strength decline , has been recognised as a powerful predictor of multi-morbidity , disability  and mortality , and is a key component of frailty  and sarcopenia [1, 6] in young old (aged ≥65) and very old adults (aged ≥85). Because of the increasing public health burden associated with low muscle strength and poor physical functioning , it is important to identify risk factors and biological mechanisms that underlie the relationship between advancing age and decline in muscle strength.
To the best of our knowledge, this is the first prospective evaluation of the relationship between summary variables of inflammation (produced by PCA) and GS decline in the very old (aged ≥85). Utilising data from the Newcastle 85+ Study, we found that three components could be used to summarise 7 inflammatory biomarkers (basal and stimulated IL-6 and TNF-α in PBMC, hsCRP, HCY and albumin) previously identified in the literature to be associated with low muscle strength (GS) in older adults. Only Component 3 (‘hsCRP-related component’) was inversely associated with GS initially but not with 5-year GS decline after adjustment for important confounders. The results suggest a role of the hsCRP-related but not the cytokine-related inflammatory component for muscle strength in very old adults.