Physical function decline and degradation of postural sway dynamics in asymptomatic sedentary postmenopausal women

Postural control is an important aspect of physical functioning. To determine whether postural sway complexity could discriminate asymptomatic sedentary postmenopausal women with normal or subnormal physical function from those with lower physical function. Cross-sectional study. Department of Geriatrics, University Hospital of Montpellier. 126 community-dwelling women aged 55 to 76 recruited though public meetings aimed at promoting physical activity in postmenopausal women. Women were asked to stand still on a force platform, either with eyes open (EO) or eyes closed (EC). Physical function was estimated using the Six-Minute Walking Distance (6MWD) test, expressed as a percentage of the predicted 6MWD (%-pred 6MWD) based on age, gender, body height, and weight. In addition to traditional stabilometric measures, dynamical measures (percentage of determinism of recurrence quantification analysis [DETRQA], sample entropy [SampEn] and complexity index of multiscale entropy [CIMSE]) were used to quantify the complexity of center of pressure (COP) time series (DETRQA: predictability, SampEn: regularity, CIMSE: multiscale regularity). None of the traditional stabilometric measures differentiated women with lower (%-pred 6MWD a parts per thousand currency sign 85.5%) from those with subnormal or normal (%-pred 6MWD > 85.5%) physical function. Conversely, women with lower physical function showed lower SampEn values in the AP direction in both EO and EC conditions, as well as lower SampEn and higher DETRQA values in the ML direction in EC condition. No significant difference in the CIMSE values was found between the two groups. Lower physical function was found to be associated with lower postural sway complexity (higher regularity and predictability) in asymptomatic sedentary postmenopausal women, especially in the absence of vision. Future work is needed to determine whether a decrease in postural sway complexity could predict future decline in physical function in these women.