Functional Impact of 10 Days of Bed Rest in Healthy Older Adults

Bed rest induces significant loss of leg lean mass in older adults. Systemic and tissue inflammation also accelerates skeletal muscle loss, but it is unknown whether inflammation is associated to inactivity-induced muscle atrophy in healthy older adults. We determined if short-term bed rest increases toll-like receptor 4 (TLR4) signaling and pro-inflammatory markers in older adult skeletal muscle biopsy samples. Six healthy, older adults underwent seven consecutive days of bed rest. Muscle biopsies (vastus lateralis) were taken after an overnight fast before and at the end of bed rest. Serum cytokine expression was measured before and during bed rest. TLR4 signaling and cytokine mRNAs associated with pro- and anti-inflammation and anabolism were measured in muscle biopsy samples using Western blot analysis and qPCR. Participants lost ∼4% leg lean mass with bed rest. We found that after bed rest, muscle levels of TLR4 protein expression and interleukin-6 (IL-6), nuclear factor-κB1, interleukin-10, and 15 mRNA expression were increased after bed rest ( P < 0.05). Additionally, the cytokines interferon-γ, and macrophage inflammatory protein-1β, were elevated in serum samples following bed rest ( P < 0.05). We conclude that short-term bed rest in older adults modestly increased some pro- and anti-inflammatory cytokines in muscle samples while systemic changes in pro-inflammatory cytokines were mostly absent. Upregulation of TLR4 protein content suggests that bed rest in older adults increases the capacity to mount an exaggerated, and perhaps unnecessary, inflammatory response in the presence of specific TLR4 ligands, e.g., during acute illness.

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Neuromuscular Electrical Stimulation Combined with Protein Ingestion Preserves Thigh Muscle Mass But Not Muscle Function in Healthy Older Adults During 5 Days of Bed Rest

Rejuvenation Research ◽

10.1089/rej.2017.1942 ◽

2017 ◽

Vol 20 (6) ◽

pp. 449-461 ◽

Cited By ~ 26

Author(s):

Paul T. Reidy ◽

Alec I. McKenzie ◽

Preston Brunker ◽

Daniel S. Nelson ◽

Katherine M. Barrows ◽

...

Keyword(s):

Older Adults ◽

Electrical Stimulation ◽

Muscle Mass ◽

Muscle Function ◽

Neuromuscular Electrical Stimulation ◽

Bed Rest ◽

Thigh Muscle ◽

Healthy Older Adults ◽

Protein Ingestion

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Ceramide Biomarkers Predictive of Cardiovascular Disease Risk Increase in Healthy Older Adults After Bed Rest

The Journals of Gerontology Series A ◽

10.1093/gerona/glaa072 ◽

2020 ◽

Vol 75 (9) ◽

pp. 1663-1670 ◽

Cited By ~ 2

Author(s):

Jonathan J Petrocelli ◽

Alec I McKenzie ◽

Ziad S Mahmassani ◽

Paul T Reidy ◽

Gregory J Stoddard ◽

...

Keyword(s):

Older Adults ◽

Time Course ◽

Disease Risk ◽

Cardiovascular Disease Risk ◽

Bed Rest ◽

Fibroblast Growth Factor 21 ◽

Healthy Older Adults ◽

Risk Increase ◽

Organ Systems ◽

Health Complications

Abstract Acute bed rest places older adults at risk for health complications by disrupting homeostasis in many organ systems, including the cardiovascular system. Circulating ceramides are emerging biomarkers predictive of cardiovascular and metabolic health and have recently been shown to be sensitive indices of cardiovascular (CV) risk. Therefore, the purpose of this study was to characterize the time course of changes in circulating ceramides in healthy younger and older adults after 5 days of bed rest and to determine whether short-term bed rest alters CV-related circulating ceramides. We hypothesized that circulating ceramides predictive of poor cardiometabolic outcomes would increase following 5 days of bed rest. Thirty-five healthy younger and older men and women (young: n = 13, old: n = 22) underwent 5 days of controlled bed rest. Fasting blood samples collected daily during the course of bed rest were used to measure circulating ceramides, lipoproteins, adiponectin, and fibroblast growth factor 21 (FGF21) levels. The primary findings were that circulating ceramides decreased while ceramide ratios and the cardiac event risk test 1 score were increased primarily in older adults, and these findings were independent of changes in circulating lipoprotein levels. Additionally, we found that changes in circulating adiponectin, FGF21 and the 6-minute walk test (6MW) inversely correlated with CV-related circulating ceramides after bed rest. The results of this study highlight the sensitivity of circulating ceramides to detect potential CV dysfunction that may occur with acute physical disuse in aging.

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Partner-Specific Communication Deficits in Individuals With Alzheimer's Disease

American Journal of Speech-Language Pathology ◽

10.1044/2020_ajslp-19-00094 ◽

2020 ◽

pp. 1-15

Author(s):

Eun Jin Paek ◽

Si On Yoon

Keyword(s):

Alzheimer’S Disease ◽

Older Adults ◽

Alzheimer's Disease ◽

Referential Communication ◽

Sorting Task ◽

Audience Design ◽

Healthy Older Adults ◽

Communication Task ◽

Design Skills ◽

Referential Expressions

Purpose Speakers adjust referential expressions to the listeners' knowledge while communicating, a phenomenon called “audience design.” While individuals with Alzheimer's disease (AD) show difficulties in discourse production, it is unclear whether they exhibit preserved partner-specific audience design. The current study examined if individuals with AD demonstrate partner-specific audience design skills. Method Ten adults with mild-to-moderate AD and 12 healthy older adults performed a referential communication task with two experimenters (E1 and E2). At first, E1 and participants completed an image-sorting task, allowing them to establish shared labels. Then, during testing, both experimenters were present in the room, and participants described images to either E1 or E2 (randomly alternating). Analyses focused on the number of words participants used to describe each image and whether they reused shared labels. Results During testing, participants in both groups produced shorter descriptions when describing familiar images versus new images, demonstrating their ability to learn novel knowledge. When they described familiar images, healthy older adults modified their expressions depending on the current partner's knowledge, producing shorter expressions and more established labels for the knowledgeable partner (E1) versus the naïve partner (E2), but individuals with AD were less likely to do so. Conclusions The current study revealed that both individuals with AD and the control participants were able to acquire novel knowledge, but individuals with AD tended not to flexibly adjust expressions depending on the partner's knowledge state. Conversational inefficiency and difficulties observed in AD may, in part, stem from disrupted audience design skills.

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Talk or Walk? Gait Speed over Self-Report in Association with Cognitive Speed in Healthy Older Adults

GeroPsych ◽

10.1024/1662-9647/a000202 ◽

2019 ◽

Vol 32 (1) ◽

pp. 41-52

Author(s):

Matthew C. Costello ◽

Shane J. Sizemore ◽

Kimberly E. O’Brien ◽

Lydia K. Manning

Keyword(s):

Older Adults ◽

Older Adult ◽

Gait Speed ◽

Well Being ◽

Self Report ◽

Subjective Report ◽

Healthy Older Adults ◽

Relative Value ◽

Cognitive Speed ◽

Age Range

Abstract. This study explores the relative value of both subjectively reported cognitive speed and gait speed in association with objectively derived cognitive speed. It also explores how these factors are affected by psychological and physical well-being. A group of 90 cognitively healthy older adults ( M = 73.38, SD = 8.06 years, range = 60–89 years) were tested in a three-task cognitive battery to determine objective cognitive speed as well as measures of gait speed, well-being, and subjective cognitive speed. Analyses indicated that gait speed was associated with objective cognitive speed to a greater degree than was subjective report, the latter being more closely related to well-being than to objective cognitive speed. These results were largely invariant across the 30-year age range of our older adult sample.

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