Self-reported Reasons for Changes in Performance of Daily Activities During a 2-Year Multidisciplinary Multiple Sclerosis Rehabilitation.

Background: Few multidisciplinary rehabilitation studies with a heterogeneous design have focused on individuals with multiple sclerosis (MS). This study compared subjective-reported changes in performance and satisfaction with daily activities among moderately and severely disabled individuals with MS during a 2-year, multidisciplinary, group-based, outpatient rehabilitation program comprising education in self-management and compensatory techniques, exercise, and guided peer support. Methods: Thirty-eight adults with moderate disability (Expanded Disability Status Scale [EDSS] score of 4.0-5.5, 74% women, mean age of 48) and 41 individuals with severe disability (EDSS 6.0-8.5, 63% women, mean age of 48) were assessed at baseline and after 12 and 21 months of outpatient rehabilitation using the Canadian Occupational Performance Measure (COPM). Group × time interactions were analyzed using mixed analysis of variance. Participants' explanations of reasons for changes in activity performance were collected via semistructured interviews and analyzed content. Results: Statistically significant improvements in COPM performance and satisfaction scores were reported in both groups from baseline to 21 months of rehabilitation. No significant between-group differences in improvement were observed. The self-reported reasons for improvement were mainly linked to environmental factors. Conclusions: The outpatient rehabilitation program, including 4 themes-cognition, mood, energy conservation, and body control-improved the self-reported performance of patients with MS with moderate and severe disabilities. Environmental factors warrant consideration during rehabilitation.

Predictors of Participation and Autonomy in People With Multiple Sclerosis.

IMPORTANCE: Because multiple sclerosis (MS) affects many life areas, it is important to know how participation and autonomy are associated with the perceived impact of MS on everyday life. OBJECTIVE: To investigate how perceived quality of life, disease impact, gender, and disease severity predict participation and autonomy in people with MS. DESIGN: Cross-sectional study in which structural equation modeling was used to evaluate relationships between measured variables. SETTINGS: Outpatient clinics in three areas and one inpatient rehabilitation center in Finland. PARTICIPANTS: Convenience sample of 194 people with MS. OUTCOMES AND MEASURES: Participants completed the Impact on Participation and Autonomy (IPA), the World Health Organization Quality of Life-Brief measure (WHOQOL-BREF), and the Multiple Sclerosis Impact Scale (MSIS-29). The Expanded Disability Status Scale (EDSS) was administered by a neurologist. RESULTS: The final model showed good fit to the data. All the goodness-of-fit indexes except χ² supported the model, χ²(30, N = 194) = 46.729, p < .026; comparative fit index = .983; Tucker-Lewis index = .969; root mean square error of approximation = .054; standardized root mean square residual = .039. Quality of life (WHOQOL-BREF) and the impact of multiple sclerosis (MSIS-29) were the main predictors of participation and autonomy. Disease severity influenced only the IPA Autonomy Indoors domain. Gender was not associated with participation and autonomy. CONCLUSION AND RELEVANCE: Experiences of participation and autonomy appear to be closely associated with perceived quality of life and impact of the disease. Findings support the importance of assessing participation and autonomy and planning interventions using this information. WHAT THIS ARTICLE ADDS: The IPA appears to be an appropriate measure for assessing participation and autonomy and planning occupational therapy interventions for people with MS. In particular, environmental factors affecting participation and autonomy should be considered when planning interventions to promote participation and autonomy.

Psychometric evaluation of the Finnish version of the impact on participation and autonomy questionnaire in persons with multiple sclerosis.

OBJECTIVE: The objective of this study was to evaluate the psychometric properties of the impact on participation and autonomy (IPA) questionnaire. The Finnish version of IPA (IPAFin) was translated into Finnish using the protocol for linguistic validation for patient-reported outcomes instruments. METHODS: A total of 194 persons with multiple sclerosis (MS) (mean age 50 years SD 9, 72% female) with moderate to severe disability participated in this study. A confirmatory factor analysis (CFA) was used to confirm the four factor structure of the IPAFin. The work and educational opportunities domain was excluded from analysis, because it was only applicable to 51 persons. Internal consistency was investigated by calculating Cronbach's alpha. RESULTS: CFA confirmed the construct validity of the IPA (standardized root mean square residual (SRMR) = 0.06, comparative fit index (CFI) = 0.93, Tucker-Lewis index =0.93, root mean square error of approximation (RMSEA) = 0.06), indicating a good fit to the model. There was no difference in the models for females and males. Cronbach's alpha for the domains ranged between 0.80 and 0.91, indicating good homogeneity. CONCLUSIONS: The construct validity and reliability of the IPAFin is acceptable. IPAFin is a suitable measure of participation in persons with MS.

Fatigue and depressive symptoms in older people.

Fatigue is considered an important indicator of aging-related declines in health and functional abilities. Previous studies have indicated strong associations between fatigue and depressive symptoms among younger populations and in patient groups with specific diseases. However, it is not known how different measures of fatigue are associated with depressive symptoms among general older populations. The purpose of this study is to describe the prevalence of depressive symptoms among community-dwelling older adults reporting mobility-related or general feelings fatigue. The study population consisted of 75-year-old community-living individuals (n = 561). Both, mobility-related and general fatigue, were associated in a stepwise relationship with depressive symptoms: a higher level of fatigue was related to higher level of depressive symptoms. Especially major general fatigue was strongly associated with high level of depressive symptoms. It is important for professionals of the field to be aware of the associations between different measures of fatigue and depressive symptoms.

Quality of life (QOL) of older adult community choral singers in Finland.

BACKGROUND: Enhancing quality of life (QOL) of older adults is an international area of focus. Identifying factors and experiences that contribute to QOL of older adults helps promote optimal levels of functioning. This study examines the relationship between perceived benefits associated with choral singing and QOL among community-dwelling older adults. METHODS: One hundred seventeen older adults who sing in community choirs in Jyväskylä, Finland, completed self-report measures of QOL (WHOQOL-Bref), depressive symptoms, and a questionnaire about the benefits of singing in choir. Correlational analyses and linear regression models were used to examine the association between the benefits of singing in choir and QOL. RESULTS: Both correlation and regression analyses found significant relationships between the benefits of choral singing and three QOL domains: psychological, social relationships, and environment. These associations remained significant after adjusting for age and depressive symptoms. As hypothesized, older choral singers who reported greater benefits of choir singing had higher QOL in multiple domains. The older choral singers in the study also reported few symptoms of depression and high overall QOL and satisfaction with health. CONCLUSION: Results suggest that singing in a community choir as an older adult may positively influence several aspects of QOL. These results suggest that community choral singing may be one potential avenue for promoting QOL in older adults.

Mobility-related fatigue, walking speed, and muscle strength in older people.

BACKGROUND: Fatigue is an important early marker of functional decline among older people, but the mechanisms underlying this association are not fully understood. The purpose of the present study was to examine the association between mobility-related fatigue and walking speed and to test the degree to which muscle strength accounts for this association. METHODS: The study is based on baseline (n = 523) and 5-year follow-up data (n = 292) from a cohort of 75-year-old persons. Standardized assessments include self-report measures of mobility-related fatigue (score range 0-6) and medical history, as well as performance-based assessment of walking speed and maximal isometric strength of knee extension, body extension, and handgrip. RESULTS: In the cross-sectional baseline analysis, one unit increase in fatigue score was associated with 0.03 m/s (ß = -.03, p < .001) and 0.05 m/s (ß = -.05, p < .001) slower maximum walking speed among women and men, respectively, while adjusting for important covariates. Among women, muscle strength accounted up to 21% and among men up to 24% for the association. In the prospective analysis, fatigue at baseline was predictive of change in walking speed among men (ß = -.04, p < .001) but not among women (ß = -.005, p = .64). Among men, muscle strength accounted up to 15% for the association between baseline fatigue and change in maximum walking speed. CONCLUSIONS: Mobility-related fatigue is associated with slower walking speed in older adults. The results suggest that muscle strength is one of the underlying factors explaining this association.

Psychomotor speed in a random sample of 7,979 subjects aged 30 years and over.

BACKGROUND AND AIMS: Slowing of psychomotor speed among older individuals has been shown in numerous studies. However, in most cases these studies were based on small and selected groups of people and, in some cases, the test procedures did not allow separation of decision time and motor components of the overall performance. The purpose of the present study was to analyse in a large, randomly selected population sample the differences in decision and movement times in simple and multiple-choice test conditions. The association of educational background with psychomotor speed was also examined. METHODS: Data on psychomotor speed were collected from a representative nation- wide sample of the Finnish population aged 30 years and over (n=7979) with the help of a computerized device in simple and multiple-choice test conditions, with visual stimuli. Background information (education) was collected by a structured interview. RESULTS: Results showed a systematic and significant decline in both decision time and movement time when proceeding from the youngest (30-39-year-olds) to the oldest (80+ yrs) age groups. This decline was more pronounced in the multiple-choice test than in the simple test. In both test conditions, movement times were shorter in men than in women. In the young and middle-aged groups, participants with longer formal education were faster than the less educated subjects. CONCLUSIONS: On the basis of the large representative random sample of this study, it may be concluded that decline in psychomotor speed during aging can already be seen at a quite young age. Decline accelerates after the age of about 70. Differences in socio-economic background factors, such as education, may modify the differences observed between younger and older individuals. These results emphasize the need for the separation of decision time and movement time in psychomotor speed tests, when differences between age groups as well as between men and women are analysed.

Psychomotor slowness is associated with self-reported sleep duration among the general population.

Short and long self-reported sleep durations have been found to be associated with several seemingly disparate health risks and impaired functional abilities, including cognitive functioning. The role of long sleep is especially poorly understood in this context. Psychomotor slowness, shown to have analogous associations with cognitive performance and health risks as self-reported long sleep duration, has not been studied together with sleep duration in epidemiological settings. We hypothesized that self-reported habitual sleep duration, especially long sleep, is associated with slow psychomotor reaction time, and that this association is independent of vigilance-related factors. The hypothesis was tested in a sample of 5352 individuals, representing the general adult population. We found a U-shaped association between self-reported sleep duration and psychomotor speed, which prevailed even after controlling for several pertinent confounders. This novel finding can be interpreted to mean that self-reported sleep duration, at least in the case of long sleep, is an indicator of bodily/brain integrity and, taken together with the results of cognitive epidemiology, may provide some new insights into the mechanisms underlying the associations between habitual self-reported sleep duration, health risks and impaired functional abilities.

Mobility performance and its sensory, psychomotor and musculoskeletal determinants from age 75 to age 80.

BACKGROUND AND AIMS: Prospective studies on the simultaneous effects of multiple determinants on objectively assessed mobility are few. The aim of this study was to analyse mobility performance, its stability and sensory, psychomotor and musculoskeletal determinants in an older population from age 75 to age 80. METHODS: Sixty-three men and 121 women aged 75 participated at baseline and, five years later, in the follow-up phase of this population-based prospective study. Maximal walking speed and step-mounting height were assessed at baseline and follow-up. Maximal isometric knee extension strength, standing balance on force platform, reaction time, visual acuity and limitations in range of motion (ROM) of hips and knees were assessed at baseline. Structural equation modeling was used to analyse the associations. RESULTS: The stability of mobility performance from baseline to the five-year follow- up was high (coefficient 0.80 in men, 0.78 in women). In men, knee extension strength, standing balance, ROM limitations and visual acuity explained 69% of the variation in mobility performance at baseline and, indirectly, 59% of that variation at follow-up. Among women, knee extension strength, standing balance, visual acuity and reaction time explained 52% of the variation of mobility performance at baseline and, indirectly, 30% at the five-year follow-up. CONCLUSIONS: Results indicate that the predictive effects of sensory, psychomotor and musculoskeletal functions on mobility performance extend over five years in older people. In seeking to prevent mobility limitations, vision, reaction time and lower extremity ROM need to be targeted, in addition to muscle strength and balance.

Sleep-related factors and mobility in older men and women.

BACKGROUND: To examine the association between sleep-related factors and measured and self-reported mobility in a representative sample of older adults. METHODS: This study included 2,825 men and women aged 55 years and older participating in a cross-sectional representative population-based Health 2000 Survey in Finland. Sleep duration, insomnia-related symptoms, and fatigue were inquired. Maximal walking speed was measured, and mobility limitation was defined as self-reported difficulties in walking 500 m or stair climbing. RESULTS: Insomnia-related symptoms and fatigue were prevalent among persons aged 65 years and older in particular. After adjusting for lifestyle factors and diseases, longer sleep (>/=9 hours) was associated with a decreased walking speed in women aged 65 or more years (p = .04) and shorter sleep (

Self-reported sleep duration and cognitive functioning in the general population.

This study investigated the relationship between self-reported sleep factors (sleep duration, insomnia, use of sleeping medicine, probable sleep apnoea and feelings of fatigue and tiredness) with cognitive functioning in 5177 people aged 30 years or older from a cross-sectional representative sample of the adult population in Finland (The Finnish Health 2000 Survey). Previous studies have indicated a U-shaped association between increased health risks and sleep duration; we hypothesized a U-shaped association between sleep duration and cognitive functioning. Objective cognitive functioning was assessed with tasks derived from the Consortium to Establish a Registry for Alzheimer's Disease test battery (verbal fluency, encoding and retaining verbal material). Subjective cognitive functioning and sleep-related factors were assessed with questionnaires. Health status was assessed during a health interview. Depressive and alcohol use disorders were assessed with the Composite International Diagnostic Interview. Medication was recorded during the health examination. Short and long sleep duration, tiredness and fatigue were found to be associated with both objectively assessed and self-reported decreased cognitive functioning. The association was stronger between sleep factors and subjective cognitive function than with objective cognitive tests. These data suggest that self-reported habitual short and long sleep duration reflect both realization of homeostatic sleep need and symptom formation in the context of the individual's health status.

Visual acuity and mortality in older people and factors on the pathway.

PURPOSE: To examine vision as a predictor of mortality in older people and the role of mobility, depressed mood, chronic diseases, body mass index, physical activity and injurious accidents in this possible association. METHODS: 223 persons aged 75 and 193 persons aged 80 years at the baseline participated in visual acuity measurements. Visual acuity (VA) of < 0.3 in the better eye was defined as visual impairment, VA of > or = 0.3 but < or = 0.5 as lowered vision and VA > 0.5 as normal VA. Death dates were received from the official register. Cox regression models were used to determine the relative risks of mortality and to study what factors lie on the pathway from poor vision to mortality. RESULTS: Over the 10-year follow-up, 107 (48%) persons aged 75 years and 138 (72%) aged 80 years at the baseline died. The risk for mortality among the 75-year-olds with lowered vision was 1.98 (95 % CI 1.25-3.13) and with visual impairment 1.90 (95% CI 1.12-3.20) compared to those with normal VA. Lower walking speed, physical inactivity, cardiovascular diseases, injurious accidents, diabetes and depressed mood each attenuated the risk markedly. Nevertheless, lowered vision remained a significant predictor of mortality even after including all these variables in the model. Among the 80-year-olds vision did not correlate with mortality. CONCLUSIONS: Lowered vision and severe visual impairment predicted mortality in the 75-year-old but not 80-year-old population. The increased risk was partially explained by lower walking speed, physical inactivity, cardiovascular diseases, depressed mood, diabetes and injurious accidents.

Force platform balance measures as predictors of indoor and outdoor falls in community-dwelling women aged 63-76 years.

BACKGROUND: Inability to maintain balance while standing increases risk of falls in older people. The present study assessed whether center of pressure (COP) movement measured with force platform technology predicts risk for falls among older people with no manifest deficiency in standing balance. METHODS: Participants were 434 community-dwelling women, aged 63-76 years. COP was measured in six stances on a force platform. Following balance tests, participants reported their falls with 12 monthly calendars. Incidence rate ratios (IRR) with 95% confidence intervals (CI) were computed from negative binomial regression models. For the analysis, those with > or =1 fall indoors were coded "indoor fallers," those with > or =1 fall outdoors, but no indoor falls, were coded "outdoor fallers." Outcome in the models was number of falls. Analyses were repeated including only participants without fall history prior to follow-up. RESULTS: Among 198 fallers, there were 57 indoor and 132 outdoor fallers. The participants in the highest COP movement tertile, irrespective of the balance test, had a two- to fourfold risk for indoor falls compared to participants in the lowest COP tertile of the test. Inability to complete the tandem stance was also a significant predictor of the fall risk. The trend for increased risk for indoor falls was found also for participants in the highest COP movement tertile and without fall history. The COP movement in balance tests was not associated with outdoor falls. CONCLUSION: Force platform balance tests provide valid information of postural control that can be used to predict fall risk even among older people without apparent balance problems or fall history. When the force platform is not available, tandem stance provides a screening tool to show increased fall risk in community-dwelling older people.

Lowered vision as a risk factor for injurious accidents in older people.

BACKGROUND AND AIMS: Poor vision in older people is often related to increased fall risk. However, the association of the severity between visual deficit and risk for all kind of injurious accidents has not been widely studied. The aim of this study was to examine whether visual loss is associated with higher incidence of injurious accidents and whether walking speed or physical activity play a mediating role in the association. METHODS: 416 persons aged 75 and 80 years at baseline underwent visual acuity measurements. Visual acuity (VA) <0.3 in the better eye, with spectacle correction when necessary, was defined as visual impairment, VA >or=0.3 but 0.5 as normal VA. Hospital records of accidents resulting in injury were monitored for 10 years after baseline. RESULTS: During the 10-year follow-up, 239 (58%) participants suffered at least one injurious accident. The risk for injurious accidents in a multivariate model adjusted for age, gender, eye-related diseases, diabetes and cardiovascular diseases among participants with lowered vision was 1.45 (95% CI 1.08- 1.94), compared with that for people with normal visual acuity. Participants with visual impairment did not have an increased risk for injurious accidents (HR 1.20, 95% CI 0.82-1.75). Furthermore, neither walking speed nor physical activity had a mediating effect on the relationship between visual loss and accidents. CONCLUSIONS: Lowered vision is a risk factor for injurious accidents in older people independent of mobility and physical activity. Interestingly, more severe visual impairment did not increase the risk. Early intervention strategies, for example, proper correction of refractive errors or cataract extraction, may potentially prevent injurious accidents in older people.

Heritability of intraocular pressure in older female twins.

PURPOSE: To examine the heritability of intraocular pressure (IOP) among older women not diagnosed as having glaucoma. DESIGN: Cross-sectional twin study. PARTICIPANTS: 94 monozygotic (MZ) and 96 dizygotic (DZ) female twin pairs aged 63-76 years and not diagnosed as having glaucoma. METHODS: Intraocular pressure was measured using a noncontact tonometer. The contributions of genetic and environmental factors to individual differences in IOP were estimated by applying an independent pathway model to twin data. MAIN OUTCOME MEASURES: Contribution of genetic and environmental effects to the variation in IOP among MZ and DZ twins. RESULTS: Mean IOP of the study population was 14.1 mmHg (+/- standard deviation 3.1) with no differences observed neither between the MZ and the DZ individuals, nor between the left and the right eyes. The pair-wise correlations for IOP of the right eye were .61 in MZ and .25 in DZ and for the left eye .63 and .42. The phenotypic correlation between the left and the right eye IOP was high (r = 0.81), suggesting that they were indices of a single trait. Quantitative genetic modeling revealed that for both eyes 64% (95% confidence interval [CI], 53-71) of the variance in IOP was explained by additive genetic effects and 18% (95% CI, 11-27) by nonshared environmental factors in common. In addition, 18% (95% CI, 15-23) of the variance in IOP was explained by nonshared environmental factors specific to each eye. CONCLUSIONS: Additive genetic influences explained most of the individual differences in IOP among older women not diagnosed as having glaucoma. Because elevated IOP is an important risk factor for glaucoma, genetic factors underlying IOP may have a significant role in determining the risk for glaucoma, a complex progressive disease leading to death of ganglion cells.

Genetic and environmental influences on hearing in older women.

BACKGROUND: This study examined the relative contribution of genetic and environmental effects on the air-conducted hearing threshold level (0.5-4 kHz) and speech recognition threshold level of the better ear as well as self-reported hearing in older women. METHODS: Hearing was measured as a part of the Finnish Twin Study on Aging in 103 monozygotic (MZ) and 114 dizygotic (DZ) female twin pairs aged 63-76 years. Audiometric measured hearing was tested using standardized methods in soundproof conditions. Self-reported hearing was assessed by a structured question. Quantitative genetic modeling was used for data analyses. RESULTS: No significant differences in age, exposure to noise, hearing-aid use, auditory diseases or accidents, or number of self-reported chronic conditions or prescription medicines were observed between the MZ and DZ twins. A genetic component in common accounted for 75% (95% confidence interval [CI], 67%-81%) of the variance in the better ear's hearing threshold level and 54% (95% CI, 43%-64%) in the better ear's speech recognition threshold level, according to a bivariate genetic analysis. In addition, 10% (95% CI, 4%-15%) of the variance in the better ear's speech recognition threshold level was explained by its specific genetic component. CONCLUSION: Individual differences in audiometrically measured air-conducted hearing threshold level (0.5-4 kHz) and speech recognition threshold level in the better ear were largely accounted for by genetic differences between individuals. In contrast, self-reported hearing appears to be accounted for solely by environmental factors.

Genetic and environmental contribution to postural balance of older women in single and dual task situations.

The purpose of the present study was to examine the effect of a second task on postural balance and to determine the role of genetic influences on postural balance when dual tasking among 206 monozygotic and 227 dizygotic female twins, aged 63-76 years. Balance was measured as medio-lateral and antero-posterior velocity of the centre of pressure (COP) (mm/s) and velocity moment (mm(2)/s) while standing on a force platform. Doing an arithmetic task increased movement of the COP while the hand motor task had no effect on movement of the COP. The genetic contribution to balance in the single task situation was minor (14%, 95% confidence interval, CI: 11-35%) whereas in the dual task situation it was moderate (28%, 95% CI: 0.02-42%). The finding can be explained in the light of the underlying phenotypes of dual tasking, such as cognitive processing that is found to be under considerable genetically controlled even in old age. Moreover, the present study supports previous studies suggesting that, especially among older people, when simultaneously maintaining balance and performing another cognitively demanding task, additional central processing is recruited.

Genetic factors and susceptibility to falls in older women.

OBJECTIVES: To determine whether genetic influences account for individual differences in susceptibility to falls in older women. DESIGN: Prospective twin cohort study. SETTING: Research laboratory and residential environment. PARTICIPANTS: Ninety-nine monozygotic (MZ) and 114 dizygotic (DZ) female twin pairs aged 63 to 76 from the Finnish Twin Cohort study. MEASUREMENTS: The participants recorded their falls on a calendar for an average+/-standard deviation of 344+/-41 days. Reported falls were verified via telephone interview, and circumstances, causes, and consequences of the fall were asked about. RESULTS: The total number of falls was 434, of which 188 were injurious; 91 participants had two or more falls. Casewise concordance was 0.61 (95% confidence interval (CI)=0.49-0.72) for MZ twins and 0.49 (95% CI=0.37-0.62) for DZ twins for at least one fall, 0.38 (95% CI=0.23-0.53) for MZ and 0.33 (95% CI=0.17-0.50) for DZ twins for at least one injurious fall, and 0.43 (95% CI=0.26-0.60) for MZ and 0.36 (95% CI=0.17-0.55) for DZ twins for recurrent falls. On average, the proportion of familial influences accounting for the individual differences in susceptibility to at least one fall was 30% and to recurrent falls was 40%; nongenetic familial and nonfamilial factors alone accounted for susceptibility to at least one injurious fall. CONCLUSION: In community-dwelling older women, familial factors underlie the risk of falling but not the risk of injurious falls.

Force platform measurements as predictors of falls among older people - a review.

BACKGROUND: Poor postural balance is one of the major risk factors for falling. A great number of reports have analyzed the risk factors and predictors of falls but the results have for the most part been unclear and partly contradictory. Objective data on these matters are thus urgently needed. The force platform technique has widely been used as a tool to assess balance. However, the ability of force platform measures to predict falls remains unknown. OBJECTIVE: The purpose of this systematic review was to extract and critically review the findings of prospective studies where force platform measurements have been used as predictors of falls among elderly populations. METHODS: The study was done as a systematic literature review. PubMed, the Cochrane Central Register of Controlled Trials, and CINAHL databases from 1950 to April 2005 were used. The review includes prospective follow-up studies using the force platform as a tool to measure postural balance. RESULTS: Nine original prospective studies were included in the final analyses. In five studies fall-related outcomes were associated with some force platform measures and in the remaining four studies associations were not found. For the various parameters derived on the basis of the force platform data, the mean speed of the mediolateral (ML) movement of the center of pressure (COP) during normal standing with the eyes open and closed, the mean amplitude of the ML movement of the COP with the eyes open and closed, and the root-mean-square value of the ML displacement of COP were the indicators that showed significant associations with future falls. Measures related to dynamic posturography (moving platforms) were not predictive of falls. CONCLUSION: Despite a wide search only a few prospective follow-up studies using the force platform technique to measure postural balance and a reliable registration of subsequent falls were found. The results suggest that certain aspects of force platform data may have predictive value for subsequent falls, especially various indicators of the lateral control of posture. However, the small number of studies available makes it difficult to draw definitive conclusions.

Contribution of genetic and environmental factors to individual differences in maximal walking speed with and without second task in older women.

BACKGROUND: Among older people, distraction while walking may increase the risk of falls. Factors underlying individual differences in dual tasking are not fully understood. Our aim was to study the effect of a second task on maximal walking speed and to examine whether individual differences in walking speed measured with and without a second task are accounted for by genetic and environmental influences shared across tasks or specific to each task. METHODS: The data were collected from the 101 monozygotic and 116 dizygotic twin pairs aged 63-76 years recruited from the Finnish Twin Cohort. Maximal walking speed (MWS) over 10 m was measured on a laboratory corridor and timed with photocells. The test was repeated while subjects performed, first, a manual task (MWSmanual) and, second, a verbal task (MWSverbal). RESULTS: Mean walking speed without a simultaneous task was 1.72 m/s (standard deviation [SD] 0.33), with a manual task it was 1.52 m/s (SD 0.26), and with a verbal task it was 1.36 m/s (SD 0.27). Multivariate genetic analysis showed that an additive genetic factor in common accounted for 17% of individual differences in MWS, 19% in MWSmanual, and 12% in MWSverbal. In addition, MWSverbal had a genetic factor specific to it accounting for 10% of the variance. Shared environmental influences, common to all three traits, accounted for 39%, 27%, and 21% of the individual differences, respectively. CONCLUSION: Approximately half of the individual differences in walking with or without another task were accounted for by genetic and nongenetic familial effects in common, and the rest of the variation was accounted for by unique environmental factors in common and factors specific to walking tests.