Associação dos metabólitos da cafeína na urina e ácido úrico sérico com a força muscular: Dados do National Health and Nutrition Examination Survey (NHANES) 2011 – 2012 & 1999 – 2002

Abstract

Background: Both oxidative stress and hyperglycemia are implicated in the decline of muscle strength. Compounds with antioxidant properties, such as certain caffeine metabolites and uric acid (UA), have shown potential in mitigating this decline. However, the specific association of these compounds with muscle strength in different age groups and glycemic statuses remains unclear. Aim: The first study aimed to investigate whether caffeine metabolites in urine are associated with muscle strength in both young and older adults. The second study, in turn, aimed to examine whether there is an association between serum uric acid levels and muscle strength in the older adults, stratified by glycated hemoglobin levels. Methods: Two cross-sectional studies were conducted using data from the National Health and Nutrition Examination Survey (NHANES). The first study, utilizing data from the 2011-2012 biennium, included 1,145 individuals aged over 20 years and evaluated the association between caffeine metabolites in urine and muscle strength using linear regression analysis. The second study, using data from the 1999-2000 and 2001-2002 biennia, involved 2,380 individuals aged 50 to 85 years, examining the relationship between serum uric acid levels and muscle strength according to glycemic status, also employing linear regression analysis. Linear regression analyses in both studies were adjusted for confounders. Results: In the first study, positive associations were observed between caffeine metabolites and muscle strength, such as 7-methyluric acid (β = 0.029; p = 0.021), 1,3-dimethyluric acid (β = 0.008; p = 0.004), 3,7-dimethyluric acid (β = 0.645; p = 0.012), 3-methylxanthine (β = 0.020; p = 0.002), 7-methylxanthine (β = 0.020; p = 0.006), 1,3-dimethylxanthine (theophylline) (β = 0.030; p = 0.004), and 3,7-dimethylxanthine (theobromine) (β = 0.035; p = 0.029) in older adults. In contrast, none of these associations were observed in young individuals. In the second study, the tertile of uric acid levels showed a positive association with peak strength in individuals with hyperglycemia (p-trend = 0.013), but not in those with normoglycemia (p-trend = 0.077). Additionally, continuous uric acid values were positively associated with muscle strength in elderly individuals with hyperglycemia (β = 5.2; (IC = 0.6; 9.8); p = 0.027), while no association was observed in those with normal glycemia (β = 2.4 (IC =−2.1; 6.9); p = 0.282). Conclusion: The first study indicates a positive association between certain caffeine metabolites in urine and muscle strength in older adults, but not in younger individuals. Conversely, the second study observed that serum UA shows a positive association with muscle strength in older adults with hyperglycemia; however, this association is not observed in individuals with normal glucose levels. The findings from both studies suggest that antioxidants, such as caffeine metabolites and uric acid, play an important role in maintaining muscle strength in populations where strength loss is associated with oxidative stress, such as older adults and individuals with hyperglycemia