title: An elevation of resting metabolic rate with declining health in nonagenarians may be associated with decreased muscle mass and function in women and men, respectively.
abstract: Previously, we showed that FI34, a frailty index based on 34 health and function ability variables, is heritable and a reliable phenotypic indicator of healthy aging. We have now examined the relationship between major components of energy expenditure and the FI34 in participants of the Louisiana Healthy Aging Study. Resting metabolic rate was associated with FI34, even after adjustment for fat-free mass, fat mass, age, sex, thyroid hormones, and insulin-like growth factor 1 levels, in multiple regression analyses. In contrast, there was no association between total daily energy expenditure and FI34. Circulating creatine phosphokinase, a clinical marker of muscle damage, was also significantly associated with FI34. However, these associations of resting metabolic rate with FI34 were restricted to the oldest old (≥90 years) and absent in younger age groups. In oldest old men, the association of FI34 with creatine phosphokinase persisted, whereas in the oldest old women, only the association with resting metabolic rate pertained with the appearance of an effect of body size and composition. These results point toward an increasing metabolic burden for the maintenance of homeodynamics as health declines in nonagenarians, and this has implications for contraction of metabolic reserve that may potentially accelerate the path to disability.
authors.affiliation: Department of Medicine, Tulane Center for Aging, Tulane University Health Sciences Center, New Orleans, Louisiana. skim5@tulane.edu.
authors.forename: Sangkyu
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Medicine, Louisiana State University Health Sciences Center, New Orleans.
authors.forename: David A
authors.initials: DA
authors.lastname: Welsh
authors.affiliation: Pennington Biomedical Research Center, Baton Rouge, Louisiana.
authors.forename: Eric
authors.initials: E
authors.lastname: Ravussin
authors.affiliation: Department of Kinesiology and.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Welsch
authors.affiliation: Department of Psychology, Louisiana State University, Baton Rouge.
authors.forename: Katie E
authors.initials: KE
authors.lastname: Cherry
authors.affiliation: Department of Biostatistics and Bioinformatics, School of Public Health and Tropical Medicine, Tulane University Health Sciences Center, New Orleans, Louisiana.
authors.forename: Leann
authors.initials: L
authors.lastname: Myers
authors.affiliation: Department of Medicine, Tulane Center for Aging, Tulane University Health Sciences Center, New Orleans, Louisiana.
authors.forename: S Michal
authors.initials: SM
authors.lastname: Jazwinski
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001481:Basal Metabolism / Q000502:physiology*; D015992:Body Mass Index; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D012146:Rest / Q000502:physiology*; D055948:Sarcopenia / Q000378:metabolism* / Q000503:physiopathology; D055815:Young Adult
keywords: Age; Aging.; Energy metabolism; Frailty