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Biomedical subjects

Stephen R Lord

Publications and source records attributed to Stephen R Lord.

47 records · Page 3Linked to original sources
PubMed2003

A physiological profile approach to falls risk assessment and prevention.

The purpose of this perspective article is to describe the use of a physiological profile approach to falls risk assessment and prevention that has been developed by the Falls and Balance Research Group of the Prince of Wales Medical Research Institute, Sydney, Australia. The profile's use for people with a variety of factors that put them at risk for falls is discussed. The Physiological Profile Assessment (PPA) involves a series of simple tests of vision, peripheral sensation, muscle force, reaction time, and postural sway. The tests can be administered quickly, and all equipment needed is portable. The results can be used to differentiate people who are at risk for falls ("fallers") from people who are not at risk for falls ("nonfallers"). A computer program using data from the PPA can be used to assess an individual's performance in relation to a normative database so that deficits can be targeted for intervention. The PPA provides valid and reliable measurements that can be used for assessing falls risk and evaluating the effectiveness of interventions and is suitable for use in a range of physical therapy and health care settings.

Accidental Falls↗
PubMed2002

Galvanic vestibular stimulation evokes sensations of body rotation.

Psychophysical experiments identified effects of galvanic vestibular stimulation (GVS) on the perception of whole-body angular rotation. Subjects lay supine on a platform that could rotate about a vertical axis through the vestibular axis so that linear movements were excluded. Movements were applied sufficiently above perception threshold to enable a reliable report of direction and movement size. In some trials, binaural GVS was applied concurrently at 1-2 mA. When GVS that was incongruent with the movement was applied, subjects reported lesser spin, on average cancelling the movement perception. When the GVS and movement were congruent, subjects reported greater spin. We conclude that GVS produces a vestibular signal of rotation, probably though an effect on semicircular canals.

Adult↗
PubMed2002

Multifocal glasses impair edge-contrast sensitivity and depth perception and increase the risk of falls in older people.

OBJECTIVES: To determine the extent to which multifocal glasses impair contrast sensitivity and depth perception at critical distances required for detecting hazards in the environment and whether multifocal glasses use increases the risk of falls in older people. DESIGN: One-year prospective cohort study. SETTING: Falls Laboratory, Prince of Wales Medical Research Institute. PARTICIPANTS: One hundred fifty-six community-dwelling people aged 63-90. MEASUREMENTS: Contrast sensitivity, depth perception, accidental falls. RESULTS: Eighty-seven subjects (55.8%) were regular wearers of multifocal (bifocal, trifocal, or progressive lens) glasses. These subjects performed significantly worse in the distant depth perception and distant edge-contrast sensitivity tests in conditions that forced them to view test stimuli through the lower segments of their glasses. Multifocal glasses wearers were more than twice as likely to fall in the follow-up period than nonmultifocal glasses wearers (odds ratio (OR) = 2.29, 95% confidence interval (CI) = 1.06-4.92), when adjusting for age, poor vision, reduced lower limb sensation and strength, slow reaction time, and increased postural sway. Multifocal glasses wearers were also more likely to fall because of a trip (OR = 2.79, 95% CI = 1.08-7.22), when outside their homes (OR = 2.55, 95% CI = 1.14-5.70), and when walking up or down stairs (P <.01). The population attributable risks of regular multifocal glasses use were 35.2% for any falls, 40.9% for falls due to a trip, and 40.9% for falls outside the home. CONCLUSIONS: The study findings indicate that multifocal glasses impair depth perception and edge-contrast sensitivity at critical distances for detecting obstacles in the environment. Older people may benefit from wearing nonmultifocal glasses when negotiating stairs and in unfamiliar settings outside the home.

Accidental Falls↗
PubMed2002

Risk of falling: predictors based on reduced strength in persons previously affected by polio.

OBJECTIVES: To examine the contributions of sensorimotor factors to postural control and falling in people with prior polio and to determine whether these contributions differ from those found in normal populations. DESIGN: Survey and case-control study. SETTING: A falls and balance laboratory in Australia. PARTICIPANTS: Forty persons with prior polio (age range, 28-71 y) and 38 age- and sex-matched control subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Lower-limb muscle strength, sway, vision, lower-limb sensation, reaction time, foot-tapping speed, and falls. RESULTS: Compared with the control subjects, the prior polio subjects performed similarly in sensory tests but worse in tests that involved a motor component. Within the prior polio group, lower-limb strength was strongly associated with postural sway on a compliant surface and explained more of the variance in sway than in control subjects. Prior polio subjects who fell multiple times had reduced lower-limb strength, slower reaction time, lower foot-tapping speed, and increased sway compared with those who fell less often. However, the rate of decline in lower-limb strength within the prior polio group did not exceed normal, age-related changes. CONCLUSIONS: This investigation of prior polio subjects provides an appropriate model for studying muscle weakness as a falls risk factor. Weakness was directly associated with falls, and had an indirect effect mediated through increased sway.

Accidental Falls↗
PubMed2002

Physiologic, psychologic, and health predictors of 6-minute walk performance in older people.

OBJECTIVE: To determine the extent to which physiologic, psychologic, and health-related factors predict 6-minute walk distance (6MWD) in older people. DESIGN: Cross-sectional study. SETTING: Retirement villages. PARTICIPANTS: A total of 515 people between the ages of 62 and 95 years (mean +/- standard deviation, 79.5+/-6.4y) residing in retirement villages in Australia. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Quantitative tests of vision, strength, peripheral sensation, reaction time, and balance and short Mini-Mental State Examination, Geriatric Depression Scale, Positive and Negative Affect Schedule (PANAS), Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), and 6MWD. RESULTS: All physiologic, psychologic, and health scores were significantly associated with 6MWD. Multiple regression analysis revealed that 10 factors (visual contrast sensitivity, lower-limb strength, simple reaction time, postural sway, maximal balance range, PANAS positive scale score, SF-36 pain score, number of medications used, SF-36 general health subscale score, age) were significant and independent predictors of 6MWD performance. Of these measures, strength, maximal balance range, medication use, and age explained the largest proportions of the variance in 6MWD. The final regression model explained over half (52.5%) of the variance in 6MWD (multiple r=.72). CONCLUSIONS: In older people, 6MWD depends on multiple physiologic, psychologic, and health factors. Thus, 6MWD appears to provide a measure of overall mobility and physical functioning in this population group rather than a specific measure of cardiovascular fitness.

Age Distribution↗
PubMed2002

Blood pressure changes on upright tilting predict falls in older people.

BACKGROUND: orthostatic hypotension may be an important risk factor for falls, though this has not yet been demonstrated in prospective studies. This may be because conventional methods of measuring blood pressure changes are too imprecise and not optimally timed. OBJECTIVES: to determine whether changes in blood pressure induced by upright tilt are associated with falls in older people, and whether medication use and symptoms of dizziness are associated with blood pressure changes and falls. METHODS: seventy men and women aged 62-92 years participated. We measured blood pressure with a plethysmograph monitor continuously before and after upright tilt. We recorded medication use and symptoms of dizziness in response to the tilt. Subjects were then followed up for 12 months to determine the incidence of falls. RESULTS: subjects who fell in the follow-up period had significantly greater decreases in systolic blood pressure when tilted than those who did not fall. Furthermore, those who had unstable systolic blood pressure during the 3 minutes after tilting, in addition to large blood pressure drops, had a two-fold increased risk of falling compared with those with neither of these conditions. Symptoms of dizziness on tilting were uncommon and not associated with blood pressure or heart rate changes, medication use, or falls incidence. Antidepressant and antihypertensive medication use were associated with decreases in diastolic rather than systolic blood pressure, but were not associated with falls. CONCLUSIONS: these findings indicate that both the decrease in blood pressure and the unstable nature of the blood pressure response following upright tilt are useful predictors of falls in older people.

Accidental Falls↗
PubMed2002

Sit-to-stand performance depends on sensation, speed, balance, and psychological status in addition to strength in older people.

BACKGROUND: Sit-to-stand (STS) performance is often used as a measure of lower-limb strength in older people and those with significant weakness. However, the findings of recent studies suggest that performance in this test is also influenced by factors associated with balance and mobility. We conducted a study to determine whether sensorimotor, balance, and psychological factors in addition to lower-limb strength predict sit-to-stand performance in older people. METHODS: Six hundred and sixty nine community-dwelling men and women aged 75-93 years (mean age 78.9, SD = 4.1) underwent quantitative tests of strength, vision, peripheral sensation, reaction time, balance, health status, and sit-to-stand performance. RESULTS: Many physiological and psychological factors were significantly associated with sit-to-stand times in univariate analyses. Multiple regression analysis revealed that visual contrast sensitivity, lower limb proprioception, peripheral tactile sensitivity, reaction time involving a foot-press response, sway with eyes open on a foam rubber mat, body weight, and scores on the Short-Form 12 Health Status Questionnaire pain, anxiety, and vitality scales in addition to knee extension, knee flexion, and ankle dorsiflexion strength were significant and independent predictors of STS performance. Of these measures, quadriceps strength had the highest beta weight, indicating it was the most important variable in explaining the variance in STS times. However, the remaining measures accounted for more than half the explained variance in STS times. The final regression model explained 34.9% of the variance in STS times (multiple R =.59). CONCLUSIONS: The findings indicate that, in community-dwelling older people, STS performance is influenced by multiple physiological and psychological processes and represents a particular transfer skill, rather than a proxy measure of lower limb strength.

Age Factors↗
PubMedDate not supplied

Predictors of falling in elderly hospital patients.

A prospective study was conducted to determine whether a brief clinical assessment conducted soon after admission can accurately identify older people who fall while staying in an acute hospital. Eighty-eight non-bedfast patients aged 80-99 years took part in the study. Within 3 days of admission, these patients were assessed for the following measures: impaired orientation on the MMSE, psychoactive medication use, evidence of stroke, and impaired ability on the Get-Up-and-Go-test. The major presenting condition for each patient was also recorded. Patients were then followed up to determine whether they fell while in hospital. Impaired orientation on the MMSE, evidence of previous cerebrovascular accident, and major presenting conditions of falls and confusion were significantly associated with falls while in hospital. There was also a trend indicating that psychoactive medication use was elevated in the fallers. In contrast, there was no difference in the proportion of fallers and non-fallers who had impaired ability in the Get-Up-and-Go-test. Of the 15 patients who fell, 13 had two or more risk factors, and after controlling for possible confounding factors of age, sex and length of stay, the presence of two-plus risk factors remained strongly and significantly associated with falls (adjusted OR = 13.43; 95% CI = 1.91 - 94.40). The findings indicate that a simple screening protocol can accurately identify patients at risk of falling while in hospital.

Accidental Falls↗
PubMedDate not supplied

Physiological and psychological predictors of walking speed in older community-dwelling people.

BACKGROUND: Six-metre walking speed (SMWS) is a commonly used test for measuring functional performance in older people. However, apart from lower limb strength, few studies have examined the range of physiological and psychological factors that influence performance in this test. OBJECTIVE: To investigate the relative contributions of a range of sensorimotor, balance and psychological factors to SMWS in a large sample of older people. METHODS: 668 community-dwelling people aged 75-98 years (mean age 80.1, SD = 4.4) underwent the SMWS test as well as quantitative tests of vision, peripheral sensation, strength, reaction time, balance, fear of falling, pain and vitality. RESULTS: Many physiological and psychological factors were significantly associated with SMWS in univariate analyses. Stepwise multiple regression analyses revealed that a composite lower limb strength measure (sum of knee extension, knee flexion and ankle dorsiflexion muscle strength scores), postural sway, leaning balance as assessed with the coordinated stability test, reaction time, edge contrast sensitivity, SF12 body pain and vitality scores and age were significant and independent predictors of SMWS. Of these measures, the combined lower limb strength measure had the highest beta weight indicating it was the most important variable in explaining the variance in SMWS. However, the other sensorimotor, balance and psychological measures each provided important independent information. The combined set of variables explained 40% of the variance in SMWS (multiple r = 0.63). CONCLUSIONS: The findings indicate that in community-dwelling older people, self-selected walking speed is influenced not only by lower limb strength but also by balance, reaction time, vision, pain and emotional well-being.

Aged, 80 and over↗
PubMedDate not supplied

Reliability of clinical tests of foot and ankle characteristics in older people.

Lower-extremity problems are common in older people; however, the reliability of clinical tools used to assess foot and ankle characteristics has not been rigorously evaluated. This study evaluated the test-retest reliability of a battery of simple clinical tests of foot and ankle characteristics (tactile sensitivity of the first metatarsophalangeal joint, navicular height, foot length and width, hallux valgus severity, an overall foot problem score, ankle flexibility, ankle dorsiflexion strength, and foot pain) in 31 individuals (13 men and 18 women) aged 76 to 87 years recruited from the community. Three examiners performed the tests on two occasions approximately 2 weeks apart. Intraclass correlation coefficients and coefficients of variation were calculated for continuously scored tests, and the kappa statistic (kappa) was used to determine the reliability of hallux valgus severity grading. All of the continuously scored tests had acceptable reliability (intraclass correlation coefficients of 0.64 to 0.98; coefficients of variation of 0.6% to 15.0%), as did hallux valgus severity grading (kappa = 0.77; absolute percentage agreement, 84%). These simple clinical tests can now be used with confidence in clinical and research settings to provide reliable and functionally important information regarding foot and ankle characteristics in older people.

Aged↗