Melatonin secretion was significantly associated with muscle strength in this elderly population. Further longitudinal studies are needed to ascertain the effect of melatonin levels on muscle strength.
Muscle strength and gait speed are related with functional limitations and disabilities and also predict cardiovascular and all-cause mortality. Nitric oxide (NO) plays an important role in regulating physiological process in skeletal muscles; however, the association between serum asymmetric dimethylarginine (ADMA) level, an endogenous competitive inhibitor of NO synthesis, and physical performance has not yet been studied. We investigated the associations of serum ADMA level with muscle strength and usual gait speed in a cross-sectional study of 550 elderly individuals (mean age, 71.2 AE 6.6 years). Mean ADMA level was 0.45 AE 0.06 mmol/L; mean grip and quadriceps strengths were 27.7 AE 8.4 kg and 165.1 AE 81.6 Nm, respectively; and mean gait speed was 1.37 AE 0.30 m/s. In multivariate linear regression analysis adjusted for potential confounding factors (age, gender, body weight, smoking and drinking status, household income, hypertension, diabetes, renal function, and physical activity), higher serum ADMA level was significantly associated with lower grip and quadriceps strengths and slower gait speed (grip strength: b, -1.257; 95% confidence interval [CI], -1.990 to -0.525; p ¼ 0.001; quadriceps strength: b, -11.730; 95% CI, -20.924 to -2.536; p ¼ 0.012; gait speed: b, -0.065; 95% CI, -0.108 to -0.022; p ¼ 0.003). Our findings indicate the significant association between serum ADMA level and physical performance among elderly individuals, which was independent of the important potential confounders.
Objectives: Prognostically, night-time blood pressure (BP) is more important than other BP parameters. Previous physiological studies suggested physical exercise continuously decreases subsequent BP levels, although the association between daytime physical activity and night-time BP has not been evaluated in large populations. Methods: This cross-sectional study of 1111 older adults (mean age, 71.8 years) measured physical activity using actigraphy and ambulatory BP parameters. Results: The mean night-time SBP and DBP were 115.9 mmHg (SD, 16.2) and 67 mmHg (8.6), respectively, and the mean average daytime physical activity was 299.2 counts/min (104.3). A multivariable linear regression analysis, adjusted for potential confounders, suggested greater average daytime physical activity was significantly associated with lower night-time SBP (regression coefficient per 100 counts/min increment, −1.18; 95% CI −2.10 to −0.26), and DBP (−0.69; 95% CI −1.17 to −0.17). Significant associations between time above activity thresholds and night-time SBP were consistently observed (≥500 counts/min: regression coefficient per log min increment, −1.61, 95% CI −3.14 to −0.08; ≥1000 counts/min: −1.00, 95% CI −1.97 to −0.03; ≥1500 counts/min: −1.13, 95% CI −2.11 to −0.14). A subgroup analysis without antihypertensive medications (n = 619) strongly associated time above activity thresholds with night-time SBP (≥500 counts/min: −2.94; 95% CI −5.20 to −0.68). These results were consistent in the analysis using dipping as a dependent variable. Conclusion: Objectively measured daytime physical activity was significantly and inversely associated with night-time BP in older adults. Further longitudinal studies would ascertain effects of physical activity on night-time BP.
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