Mahbub MH

Purpose: We investigated sex differences in heart rate variability (HRV; a non-invasive indicator of autonomic nervous system) and its frequency-specific responses to whole-body vibration (WBV) at three distinct frequencies among elderly subjects. Methods: Data from 11 males and 13 females were analyzed across four randomized sessions of exposure: WBV at 15, 20, or 25 Hz with a 4 mm peak-to-peak displacement, or control (0 Hz) condition comprising three bouts of 1-minute exposure with 1-minute between-bout rests. HRV measurements were taken before and during the exposure. Results: At baseline, low-frequency power/LF (ms^{2}) were significantly lower in females than males (P < 0.05). During exposure, LF (ms^{2}), high-frequency power (ms^{2}), standard deviation of normal-to-normal intervals, root mean square of successive differences between RR intervals, standard deviation of the Poincaré plot perpendicular to the line-of-identity, and standard deviation of the Poincaré plot along the line-of-identity significantly increased at 20 Hz for males and 25 Hz for females (P < 0.05 to 0.005) compared to respective baselines. Conclusions: Elderly females tend to exhibit reduced autonomic nervous system function compared to males. Furthermore, our results indicate that WBV at 20 Hz for males and 25 Hz for females may be considered beneficial for enhancing HRV in the elderly.

Objective: The objective was to explore the potential existence and nature of the relationship between serum of uric acid (SUA) and serum uric acid to serum creatinine ratio (SUA/SCr) with reduced estimated glomerular filtration rate (eGFR) in patients with non-alcoholic fatty liver disease (NAFLD). Methods: A cross-sectional study was conducted among apparently healthy subjects with NAFLD (n=485). The association between tertiles of SUA and SUA/SCr with reduced eGFR (n=56) were investigated after adjustments for potentially relevant confounders. Also, the diagnostic performances of SUA and SUA/SCr were evaluated with the receiver operating characteristic (ROC) curve analysis. Results: In the adjusted models, SUA showed a significant positive association with reduced eGFR in the highest tertile (OR 5.65, 95% CI 2.48-12.86, p<0.001), and SUA/SCr, in the lowest tertile (4.21, 95% CI 1.76-10.07, p=0.001). The ROC curve analysis did not reveal any significant difference between the corresponding values of area under the curve for SUA and SUA/SCr (0.70 and 0.67, respectively; p=0.521). Conclusions: We revealed significant and independent associations of elevated SUA and reduced SUA/SCr with kidney function decline in NAFLD. However, the clinical utility of these two biomarkers seemed to be limited for the mentioned purpose and needs further investigations.

Abstract Purpose: The purpose of this study was to investigate the effects of two different postures (sitting and standing) and three different ambient temperatures (10℃, 20℃, and 30℃) on heart rate variability (HRV) among healthy young adults. Methods: Twelve young adult volunteers (males 6, females 6) were recruited. Following acclimatization to any the room temperature (10℃, 20℃ or 30℃), 5-min measurements of HRV were conducted in sitting and standing postures of the subjects. Results: Compared to the sitting posture, measurements obtained in the standing posture revealed a significant decrease in high-frequency power/HF, root mean square of successive differences between RR intervals, standard deviation of Poincaré plot perpendicular to the line-of-identity or SD1 and SD1/standard deviation of Poincaré plot along the line-of-identity or SD2, and a significant increase in lowfrequency power/LF and LF/HF under all experimental conditions (p<0.05 to 0.005). Majority of HRV parameters showed significant differences while the values obtained under 10℃ were compared with 20℃ and 30℃ conditions, respectively (p<0.05 to 0.001). Conclusions: Our findings suggest the predominance of sympathetic tone in the standing compared with sitting posture. Furthermore, colder conditions caused a predominance of the parasympathetic activity in both sitting and standing postures, and such effects of ambient temperature on the sympathovagal balance were stronger in the latter posture.