[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
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.
No preview · Article · Apr 2013 · International Psychogeriatrics
[Show abstract][Hide abstract] ABSTRACT: 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.
Full-text · Article · Dec 2011 · Journal of Sleep Research
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
In the cross-sectional baseline analysis, one unit increase in fatigue score was associated with 0.03 m/s (β = -.03, p < .001) and 0.05 m/s (β = -.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 (β = -.04, p < .001) but not among women (β = -.005, p = .64). Among men, muscle strength accounted up to 15% for the association between baseline fatigue and change in maximum walking speed.
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.
No preview · Article · Oct 2011 · The Journals of Gerontology Series A Biological Sciences and Medical Sciences
[Show abstract][Hide abstract] ABSTRACT: 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.
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 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.
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.
No preview · Article · Apr 2011 · Aging clinical and experimental research
[Show abstract][Hide abstract] ABSTRACT: To examine the association between sleep-related factors and measured and self-reported mobility in a representative sample of older adults.
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.
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 (</=6 hours) with a higher odds for mobility limitation in women aged 65 or more years (odds ratio [OR] = 1.68, 95% confidence interval [CI] = 1.02-2.75) and in men aged 55-64 years (OR = 3.62, 95% CI = 1.40-9.37) compared with those having a mid-range sleep duration. Sleeping disorders or insomnia was independently associated with both decreased walking speed and mobility limitation in men aged 55 or more years but only with mobility limitation in women aged 65 or more years. Of the sleep-related daytime consequences, "weakness or tiredness" was associated with a decreased walking speed and a higher odds for mobility limitation both in men and in women aged 55 or more years.
Several sleep-related factors, such as sleep duration, insomnia-related symptoms, and fatigue, are associated with measured and self-reported mobility outcomes.
Full-text · Article · Feb 2010 · The Journals of Gerontology Series A Biological Sciences and Medical Sciences
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
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.
No preview · Article · Feb 2010 · Aging clinical and experimental research
[Show abstract][Hide abstract] ABSTRACT: 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.
Full-text · Article · Sep 2009 · Journal of Sleep Research
[Show abstract][Hide abstract] ABSTRACT: The postural sway of subjects during standing both with their eyes open and closed together with maximum velocity of walking were analysed in six male chronic hemiplegic patients before, during and after an intensive movement training programme lasting 8 weeks. The movement training programme was carried out on the basis of Bobath's principles. Three of the subjects carried out their training on a trampoline, with the particular purpose of enhancing the stimulation of the mechanisms responsible for the control of balance. During the follow-up, maximal walking velocity remained at previous levels and no systematic changes were observed in the control of postural sway. Although the use of the trampoline did not indicate special advantages for the balance or gait of these patients, its use in movement training is nevertheless encouraged as an alternative and motivational factor that might also lead to specific benefits with a training programme of longer duration.
No preview · Article · Jul 2009 · Physiotherapy Theory and Practice
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
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.
No preview · Article · Jul 2009 · Ophthalmic epidemiology
[Show abstract][Hide abstract] ABSTRACT: 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.
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 <or=0.5 as lowered vision, and VA>0.5 as normal VA. Hospital records of accidents resulting in injury were monitored for 10 years after baseline.
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.
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.
No preview · Article · Mar 2008 · Aging clinical and experimental research
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
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.
Full-text · Article · Feb 2008 · The Journals of Gerontology Series A Biological Sciences and Medical Sciences
[Show abstract][Hide abstract] ABSTRACT: To examine the heritability of intraocular pressure (IOP) among older women not diagnosed as having glaucoma.
Cross-sectional twin study.
94 monozygotic (MZ) and 96 dizygotic (DZ) female twin pairs aged 63-76 years and not diagnosed as having glaucoma.
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.
Contribution of genetic and environmental effects to the variation in IOP among MZ and DZ twins.
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.
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.
[Show abstract][Hide abstract] ABSTRACT: 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.
No preview · Article · Jul 2007 · Neurobiology of aging
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
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.
No preview · Article · May 2007 · The Journals of Gerontology Series A Biological Sciences and Medical Sciences
[Show abstract][Hide abstract] ABSTRACT: Reliable normative data for force platform measurements of postural balance have not been available.
Data on postural balance were collected from a representative nationwide sample of a Finnish population aged >or=30 years (n = 7,979). As part of a comprehensive health survey (Health 2000), postural balance was measured with the help of a force platform system in four test conditions: normal standing with eyes open and closed (both for 30 s), semi-tandem (20 s) and tandem stand with eyes open (20 s). In addition, balance abilities were also evaluated by a non-instrumented field test.
The main findings of this study indicated that the differences in balance between subjects belonging to different age categories were apparent already among young and middle-aged subjects. This is true, however, only for the more accurate force platform measurements, as the field test showed a clear ceiling effect up to 60 years of age. At higher ages both methods indicated a further, accelerating decline in balance function. In most cases, males tended to have more pronounced sway, as indicated by the speed and amplitude aspects of the movement of the center of pressure during the force platform registrations and these differences were larger in the older age groups. In contrast, in the field test a larger proportion of males were able to achieve the highest category (10 s in tandem stand) and the proportion of subjects unable to stand for a minimum of 10 s feet side by side was larger among females than males. These observations may partly be due to differences in the participation/acceptable performance in the different tests. In addition, the field test and force platform measurements may partially reflect different aspects of balance abilities.
The results of the present study provide normative values for force platform balance tests at an age of 30 years and above. Deterioration in balance function clearly starts at relatively young ages and further accelerates from at about 60 years upwards. Due to systematic differences between males and females, separate normative values for both sexes are needed. Due to marked ceiling effects the field test can only be recommended for older individuals, aged >/=60. On the other hand, force platform registrations in the more demanding tests (semi-tandem and tandem stands) suffer from floor effects in the oldest age groups.
[Show abstract][Hide abstract] ABSTRACT: To determine whether genetic influences account for individual differences in susceptibility to falls in older women.
Prospective twin cohort study.
Research laboratory and residential environment.
Ninety-nine monozygotic (MZ) and 114 dizygotic (DZ) female twin pairs aged 63 to 76 from the Finnish Twin Cohort study.
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.
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.
In community-dwelling older women, familial factors underlie the risk of falling but not the risk of injurious falls.
No preview · Article · May 2006 · Journal of the American Geriatrics Society
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
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.
[Show abstract][Hide abstract] ABSTRACT: 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.
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).
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.
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.
Full-text · Article · Nov 2005 · The Journals of Gerontology Series A Biological Sciences and Medical Sciences