title: Postural stability analysis with inertial measurement units in Alzheimer's disease.
abstract: BACKGROUND
  The cause of frequent falls in patients with Alzheimer's disease (AD) is still not well understood. Nevertheless, balance control and sensory organization are known to be critical for moving safely and adapting to the environment.
  
  
  METHODS
  We evaluated postural stability in 20 AD patients (11 fallers and 9 nonfallers) and 16 healthy controls with an inertial measurement unit (triaxial accelerometers and gyroscopes) attached to the center of mass (COM) in different balance conditions (Romberg on flat surface and frontward/backward-inclined surface, with or without visual suppression) in a motor lab.
  
  
  RESULTS
  In AD patients, the group of fallers showed a different kinetic pattern of postural stability characterized by higher vulnerability to visual suppression, higher total/maximal displacement and a mediolateral/anteroposterior range of sway, and a consequent need for more corrections of COM pitch and roll angles.
  
  
  CONCLUSIONS
  Further studies are needed to consolidate the normative values of the discriminatory kinetic variables with the potential of inclusion in a multifactorial analysis of the risk of falls. Nevertheless, these results highlight signs of impairment of central postural control in AD, which may require early therapeutic intervention.
authors.affiliation: Neurology Department, Centro Hospitalar do Alto Ave, EPE, Guimarães, Braga, Portugal ; Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal ; ICVS/3B's, PT Government Associate Laboratory, Braga/Guimarães, Braga, Portugal.
authors.forename: Miguel F
authors.initials: MF
authors.lastname: Gago
authors.affiliation: Center ALGORITMI, School of Engineering, University of Minho, Braga, Portugal.
authors.forename: Vitor
authors.initials: V
authors.lastname: Fernandes
authors.affiliation: Center ALGORITMI, School of Engineering, University of Minho, Braga, Portugal.
authors.forename: Jaime
authors.initials: J
authors.lastname: Ferreira
authors.affiliation: Center ALGORITMI, School of Engineering, University of Minho, Braga, Portugal.
authors.forename: Hélder
authors.initials: H
authors.lastname: Silva
authors.affiliation: Center ALGORITMI, School of Engineering, University of Minho, Braga, Portugal.
authors.forename: Luís
authors.initials: L
authors.lastname: Rocha
authors.affiliation: Center ALGORITMI, School of Engineering, University of Minho, Braga, Portugal.
authors.forename: Estela
authors.initials: E
authors.lastname: Bicho
authors.affiliation: Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal ; ICVS/3B's, PT Government Associate Laboratory, Braga/Guimarães, Braga, Portugal.
authors.forename: Nuno
authors.initials: N
authors.lastname: Sousa
keywords: Alzheimer's disease; Inclined surface; Inertial measurement unit; Postural stability; Triaxial accelerometer and gyroscope