Physiological factors contributing to mobility loss over 9 years of follow-up—results from the InCHIANTI study.
BACKGROUND
Mobility is an essential aspect of everyday life and enables autonomy and participation. Although many risk factors for mobility loss have been previously described, their relative importance and independent contributions to the long-term risk of losing mobility have not been well defined.


METHODS
This study is based on 1,013 men and women aged ≥65 years enrolled in 1998-2000 and followed for 9 years through 2007-2008 in the population-based InCHIANTI (Invecchiare in Chianti, aging in the Chianti area) study. We considered 44 different measures assessed at baseline to explore six subsystems: (i) central nervous system, (ii) peripheral nervous system, (iii) muscles, (iv) bone and joints, (v) energy production and delivery, and (vi) perceptual system. The outcome was incident mobility loss defined as self-report of inability to walk 400 m or climb and descend 10 steps without help from another person. Random survival forest analysis was used to rank the candidate predictors by their importance.


RESULTS
The most important physiological markers predicting mobility loss that emerged from the random survival forest modeling were older age among women (81-95 vs 65-68 years, hazard ratio [HR] 9.60 [95% CI 3.35, 27.50]), weaker ankle dorsiflexion strength (lowest vs highest quintile, HR 5.25 [95% CI 2.35, 11.72]), low hip flexion range of motion (lowest vs highest quintile, HR 2.30 [95% CI 1.20, 4.41]), presence of primitive reflexes (yes vs no, HR 1.47 [95% CI 1.03, 2.09]), and tremor (yes vs no, HR 1.91 [95% CI 1.18, 3.07]).


CONCLUSIONS
Prevention of mobility loss with aging should focus on prevention and treatment of neuromuscular impairments.
Department of Public Health, University of Turku, Finland. School of Health Sciences, University of Tampere, Finland. sari.stenholm@utu.fi.
Sari
S
Stenholm
National Institute on Aging, Baltimore, Maryland.
Michelle
M
Shardell
Azienda Sanitaria di Firenze, Geriatric Unit, Florence, Italy.
Stefania
S
Bandinelli
Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore.
Jack M
JM
Guralnik
National Institute on Aging, Baltimore, Maryland.
Luigi
L
Ferrucci
D000203:Activities of Daily Living; D000368:Aged; D000375:Aging / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D015577:Geriatric Assessment; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D051346:Mobility Limitation; D053580:Muscle Strength / Q000502:physiology; D012307:Risk Factors
Central nervous system; Mobility loss; Muscle strength; Physical functioning; Physiological markers; Random survival forest