Mechanisms of Postural Control in Alcoholic Men and Women: Biomechanical Analysis of Musculoskeletal Coordination During Quiet Standing

Abstract

Background Excessive sway during quiet standing is a common sequela of chronic alcoholism even with prolonged sobriety. Whether alcoholic men and women who have remained abstinent from alcohol for weeks to months differ from each other in the degree of residual postural instability and biomechanical control mechanisms has not been directly tested. Method We used a force platform to characterize center-of-pressure biomechanical features of postural sway, with and without stabilizing conditions from touch, vision, and stance, in 34 alcoholic men, 15 alcoholic women, 22 control men, and 29 control women. Groups were matched in age (49.4 years), general intelligence, socioeconomic status, and handedness. Each alcoholic group was sober for an average of 75 days. Results Analysis of postural sway when using all 3 stabilizing conditions vs. none revealed diagnosis and sex differences in ability to balance. Alcoholics had significantly longer sway paths, especially in the anterior-posterior direction, than controls when maintaining erect posture without balance aids. With stabilizing conditions the sway paths of all groups shortened significantly, especially those of alcoholic men, who demonstrated a 3.1-fold improvement in sway path difference between the easiest and most challenging conditions; the remaining 3 groups, each showed a ~2.4-fold improvement. Application of a mechanical model to partition sway paths into open-loop and closed-loop postural control systems revealed that the sway paths of the alcoholic men but not alcoholic women were characterized by greater short-term (open-loop) diffusion coefficients without aids, often associated with muscle stiffening response. With stabilizing factors, all four groups showed similar long-term (closed loop) postural control. Correlations between cognitive abilities and closed-loop sway indices were more robust in alcoholic men than alcoholic women. Conclusions Reduction in sway and closed-loop activity during quiet standing with stabilizing factors shows some differential expression in men and women with histories of alcohol dependence. Nonetheless, enduring deficits in postural instability of both alcoholic men and alcoholic women suggest persisting liability for falling.

Pontocerebellar volume deficits and ataxia in alcoholic men and women: no evidence for “telescoping”

“…MRI or ataxia data from smaller samples of these groups appeared in other publications (Fama et al 2007; Sullivan et al 2006; Sullivan et al 2009b, c, d), but the MRI analysis presented herein is novel, and the presentation of MRI and ataxia data from this full group of 200 alcoholic and control men and women will have been presented in abstract form only (Sullivan et al 2009a). …”

Postural Stability in Cigarette Smokers and During Abstinence from Alcohol

“…Postural sway measures (Sullivan et al, 2010) or functional gait assessments and tests of the balance evaluation systems (Leddy et al, 2011) could provide more robust and varied information in future studies of gait and balance. sCON were not re-tested and only a subset of nsCON was retested at follow-up.…”

“…A few factors limit the generalizability of our results: Only 1 measure of static postural stability was used in this analysis due to ceiling effects or inability to perform on other ataxia measures. Postural sway measures (Sullivan et al, 2010) or functional gait assessments and tests of the balance evaluation systems (Leddy et al, 2011) could provide more robust and varied information in future studies of gait and balance. sCON were not retested, and only a subset of nsCON was retested at follow-up.…”

Reduced Fronto‐Cerebellar Functional Connectivity in Chronic Alcoholic Patients

“…It is also unlikely that our observations can be explained by gender differences due to gender matching of the groups. Nevertheless, future studies are needed to determine how interactions of gender with alcohol dependence affect fronto-cerebellar connectivity, as important gender differences have been documented in alcoholism (Greenfield 2002, Schulte et al 2009, Sullivan et al 2010) as well as brain connectivity (Gong 2011, Tomasi and Volkow 2011). …”