0137 Self-Reported Sleep Quality is Associated with Central Hemodynamics in Healthy Individuals

Introduction

Insufficient sleep is associated with arterial stiffness and elevated cardiovascular disease risk. Central hemodynamics are influenced by arterial stiffness, yet independently predict cardiovascular risk. Relationships between sleep characteristics and central hemodynamic parameters are largely unexplored. We aimed to characterize the relationship between self-reported sleep quality and central hemodynamics in healthy individuals. To explore the hypothesis that impairments in glucose metabolism, resulting from lack of sleep, may underlie relationships between sleep and central hemodynamic variables, we also examined associations between self-reported sleep quality and fasting blood glucose values.

Methods

Thirty-one healthy subjects (14 females /17 males; 20–69 years) that were free from metabolic or cardiovascular disease, and that did not take sleep medication were included in the study. Relationships between self-reported sleep quality, obtained using the Pittsburgh Sleep Quality Index (PSQI), with central hemodynamic profiles(systolic and diastolic blood pressures, pulse and augmentation pressures, augmentation index) estimated from oscillometric pulse wave analysis, and fasting blood glucose values were assessed.

Results

Central pulse pressure was significantly elevated (P<0.05) in poor (PSQIscore >5) compared to normal (PSQI score 0–5) self-reported sleepers. Linear regression models, adjusted for age, gender, and body mass index, demonstrated PSQI score to be an independent predictor (P<0.05) of both central pulse (β=0.469) and augmentation (β=0.364) pressures. Global PSQI scores were not related to fasting blood glucose values (r=0.045; P>0.05).

Conclusion

Significant relationships between central pulse and augmentationpressures and self-reported sleep quality highlight the importance of considering sleep when examining lifestyle contributors to central hemodynamics.

Support

No funding.

Circulating Interleukin-6 Is Associated with Skeletal Muscle Strength, Quality, and Functional Adaptation with Exercise Training in Mobility-Limited Older Adults

BACKGROUND

Human aging is characterized by a chronic, low-grade inflammation suspected to contribute to reductions in skeletal muscle size, strength, and function. Inflammatory cytokines, such as interleukin-6 (IL-6), may play a role in the reduced skeletal muscle adaptive response seen in older individuals.

OBJECTIVES

To investigate relationships between circulating IL-6, skeletal muscle health and exercise adaptation in mobility-limited older adults.

DESIGN

Randomized controlled trial.

SETTING

Exercise laboratory on the Health Sciences campus of an urban university.

PARTICIPANTS

99 mobility-limited (Short Physical Performance Battery (SPPB) ≤9) older adults.

INTERVENTION

6-month structured physical activity with or without a protein and vitamin D nutritional supplement.

MEASUREMENTS

Circulating IL-6, skeletal muscle size, composition (percent normal density muscle tissue), strength, power, and specific force (strength/CSA) as well as physical function (gait speed, stair climb time, SPPB-score) were measured pre- and post-intervention.

RESULTS

At baseline, Spearman's correlations demonstrated an inverse relationship (P<0.05) between circulating IL-6 and thigh muscle composition (r = -0.201), strength (r = -0.311), power (r = -0.210), and specific force (r = -0.248), and positive association between IL-6 and stair climb time (r = 0.256; P<0.05). Although the training program did not affect circulating IL-6 levels (P=0.69), reductions in IL-6 were associated with gait speed improvements (r = -0.487; P<0.05) in "higher" IL-6 individuals (>1.36 pg/ml). Moreover, baseline IL-6 was inversely associated (P<0.05) with gains in appendicular lean mass and improvements in SPPB score (r = -0.211 and -0.237, respectively).

CONCLUSIONS

These findings implicate age-related increases in circulating IL-6 as an important contributor to declines in skeletal muscle strength, quality, function, and training-mediated adaptation. Given the pervasive nature of inflammation among older adults, novel therapeutic strategies to reduce IL-6 as a means of preserving skeletal muscle health are enticing.

Lower-Extremity Torque Capacity and Physical Function in Mobility-Limited Older Adults

OBJECTIVES

Skeletal muscle weakness and an increase in fatigability independently contribute to age-related functional decline. The objective of this study was to examine the combined contribution of these deficiencies (i.e., torque capacity) to physical function, and then to assess the functional implications of progressive resistance training (PRT) mediated-torque capacity improvements in mobility-limited older adults.

DESIGN

Randomized controlled trial.

SETTING

Exercise laboratory on the Health Sciences campus of an urban university.

PARTICIPANTS

Seventy mobility-limited (Short Physical Performance Battery (SPPB) ≤9) older adults (~79 yrs).

INTERVENTION

Progressive resistance training or home-based flexibility 3 days/week for 12 weeks.

MEASUREMENTS

Torque capacity was defined as the sum of peak torques from an isokinetic knee extension fatigue test. Relationships between torque capacity and performance-based and patient-reported functional measures before and after PRT were examined using partial correlations adjusted for age, sex, and body mass index.

RESULTS

Torque capacity explained (P<0.05) 10 and 28% of the variance in six-minute walk distance and stair climb time, respectively. PRT-mediated torque capacity improvements were paralleled by increases (P<0.05) in self-reported activity participation (+20%) and advanced lower extremity function (+7%), and associated (P<0.05) with a reduction in activity limitations (r=0.44) and an improved SPPB score (r=0.32).

CONCLUSION

Skeletal muscle torque capacity, a composite of strength and fatigue, may be a proximal determinant of physical function in mobility-limited older individuals. To more closely replicate the musculoskeletal demands of real-life tasks, future studies are encouraged to consider the combined interaction of distinct skeletal muscle faculties to overall functional ability in older adults.