Kara Martin

Cerebral White Matter Lesions, Gait, and the Risk of Incident Falls A Prospective Population-Based Study

Background and Purpose— The association between cerebral white matter lesions (WMLs) and the risk of falls in older people is uncertain, with no supporting prospective evidence. We aimed to determine the risk of incident falls associated with WML volume, and the interactions between WML volume, gait, and other sensorimotor factors leading to falls. Methods— We conducted a prospective, population-based study (n=294, mean age 72.3 years, independently mobile). Volumetric MRI, computerized gait measures, and sensorimotor measures of falls risk were obtained at baseline. Incident falls were recorded prospectively over a 12-month period. Using regression modeling, we estimated the risk of incident falls associated with baseline WML volume. Results— Increasing baseline WML volume was independently associated with any incident fall (P=0.01) and multiple incident falls (P=0.02). The risk of incident falls was doubled in people with lesion volumes in the highest quintile of its distribution compared with the lowest (adjusted relative risk, 2.32; 95% CI, 1.28–4.14). Greater lesion volume was also associated with poorer gait and greater gait variability (both P<0.001). The effect of WML volume on the risk of falls was magnified in people with poorer quadriceps muscle strength (P=0.03) and greater gait variability (P=0.001). Conclusions— These data provide the first prospective evidence to our knowledge demonstrating that WMLs are strong risk factors for falls in the general older population. WMLs present potential therapeutic targets for interventional trials in falls prevention.

Gait, gait variability and the risk of multiple incident falls in older people: a population-based study

BACKGROUND it is uncertain as to which measures of gait best predict those who are likely to fall. Our aim was to investigate the associations of gait and gait variability measures with incident falls risk. METHODS individuals aged 60-86 years (n = 412) were randomly selected from the Tasmanian electoral roll. Average gait and gait variability measures were collected on a computerised walkway. Falls were recorded prospectively over 12 months. Log multinomial regression was used to estimate the relative risk of single and multiple falls associated with gait measures. Covariates included age, sex, sensorimotor and cognitive measures, mood and medications. RESULTS in this population-based study greater intra-individual variability in step length and double-support phase were linearly associated with increased risk of multiple falls (P = 0.04). Non-linear associations with multiple falls were found for gait speed P = 0.002, cadence P = 0.004 and step time variability P = 0.03. None of the gait measures predicted risk of single falls. CONCLUSION there is an increased risk of multiple falls, but not single falls, in older people with poorer gait. Specific measures of gait and gait variability seem to confer this risk and may be amenable to interventions designed to reduce the risk of multiple falls in older people.

Cognitive Function, Gait, and Gait Variability in Older People: A Population-Based Study

BACKGROUND Gait impairments are associated with falls and loss of independence. The study of factors associated with poorer gait may assist in developing methods to preserve mobility in older people. The aim of this study was to examine the associations between a range of cognitive functions and gait and gait variability in a population-based sample of older people. METHODS Gait and intra-individual gait variability measures were obtained using the GAITRite walkway in a sample of older people, aged 60-85 years (N = 422), randomly selected from the Tasmanian electoral roll. Raw scores from a cognitive battery were subjected to principal component analyses deriving four summary domains: executive function/attention, processing speed, memory, and visuospatial ability. Multivariable linear regression was used to examine associations between cognitive domains and gait measures adjusting for age, sex, ambulatory activity, medication use, and mood. RESULTS The mean age of the sample was 72.0 years (SD = 7.0), with 238 men (56%). Poorer executive function was independently associated with poorer performance in most absolute gait measures and with greater variability in double support phase and step time. Processing speed was associated with absolute gait measures and double support phase variability. Visuospatial ability was only associated with greater double support phase variability, independently of executive function and processing speed. Memory was not independently associated with any gait measure. CONCLUSIONS In community-dwelling older people, executive function/attention and processing speed were associated with many aspects of gait, whereas visuospatial ability may only play a role in double support phase variability.

Cognitive Function Modifies the Effect of Physiological Function on the Risk of Multiple Falls—A Population-Based Study

BACKGROUND There is a poor understanding of the interplay between cognitive and physiological functions in leading to falls. We hypothesized that poorer physiological function would modify the effect of poorer cognitive function on increased risk of falling in older people. METHODS A range of cognitive (executive function/attention, memory, processing speed, and visuospatial ability) and physiological functions (vision, proprioception, sway, leg strength, reaction time) were measured using standardized tests in 386 randomly selected adults aged 60-86. Incident falls were recorded over 12 months. Log-multinomial regression was used to model the relationships and test for interactions between cognition and physiological function in explaining the risk of single or multiple falls. RESULTS Overall, 94 people (24.4%) had a single fall, and 78 (20.2%) had multiple falls. No significant associations were observed between cognitive function and the risk of single falls. The risk of multiple falls was increased with poorer function in Stroop dot time (RR = 1.03, 95% CI [1.01, 1.05], p = .002) and Stroop word time (RR = 1.02 [1.01, 1.03], p = .001) and reduced with better function in Category Fluency (RR = 0.94 [0.91, 0.98], p = .001) and visuospatial function (RR = 0.95 [0.92, 0.98], p < .001). These associations were amplified by the presence of greater body sway, less ambulatory physical activity, slower reaction time and gait speed, weaker muscle strength, and poorer visual contrast (p for interactions <.05). CONCLUSIONS Preventing falls due to physiological impairments in community-dwelling older people may need to be tailored based on cognitive impairment, a key factor in their inability to compensate for physical decline.

Air pollution from bushfires and their association with hospital admissions in Sydney, Newcastle and Wollongong, Australia 1994-2007

Objective : We examined the association between validated bushfire smoke pollution events and hospital admissions in three eastern Australian cities from 1994 to 2007.

Visuospatial ability and memory are associated with falls risk in older people: a population-based study

Background/Aims: Our purpose was to examine whether falls risk is associated with cognitive functions beyond executive function/attention and processing speed. Methods: Cognitive function was measured in a population-based sample (n = 300) of people aged 60–86 years. The physiological profile assessment was used to estimate the falls risk. Results: After adjusting for confounders, visual construction (p < 0.01), executive function/attention and memory (both p < 0.05) were independently associated with falls risk. The associations for visual construction (p < 0.01) and memory (p < 0.01) remained after adjusting for executive function/ attention. Conclusions: The neural basis underlying the associations of visuospatial function and memory with falls risk require further study.

Air pollution events from forest fires and emergency department attendances in Sydney, Australia 1996–2007: a case-crossover analysis

BackgroundSevere air pollution generated by forest fires is becoming an increasingly frequent public health management problem. We measured the association between forest fire smoke events and hospital emergency department (ED) attendances in Sydney from 1996–2007.MethodsA smoke event occurred when forest fires caused the daily citywide average concentration of particulate matter (PM10 or PM2.5) to exceed the 99th percentile of the entire study period. We used a time-stratified case-crossover design and conditional logistic regression models adjusted for meteorology, influenza epidemics, and holidays to estimate odds ratios (OR) and 95% confidence intervals (CI) for ED attendances on event days compared with non-event days for all non-trauma ED attendances and selected cardiorespiratory conditions.ResultsThe 46 validated fire smoke event days during the study period were associated with same day increases in ED attendances for all non-trauma conditions (1.03, 95% CI 1.02, 1.04), respiratory conditions (OR 1.07, 95% CI 1.04, 1.10), asthma (OR 1.23, 95% CI 1.15, 1.30), and chronic obstructive pulmonary disease (OR 1.12, 95% CI 1.02, 1.24). Positive associations persisted for one to three days after the event. Ischaemic heart disease ED attendances were increased at a lag of two days (OR 1.07, 95% CI 1.01, 1.15) while arrhythmias had an inverse association at a lag of two days (OR 0.91, 95% CI 0.83, 0.99). In age-specific analyses, no associations present in children less than 15 years of age for any outcome, although a non-significant trend towards a positive association was seen with childhood asthma. A further association between smoke event and heart failure attendances was present for the 15–65 year age group, but not older adults at a lag of two days (OR 1.37 95% CI 1.05, 1.78).ConclusionSmoke events were associated with an immediate increase in presentations for respiratory conditions and a lagged increase in attendances for ischaemic heart disease and heart failure. Respiratory impacts were either absent or considerably attenuated in those <15 years. Similar to previous studies we found inconsistent associations between fire smoke and cardiovascular diseases. Better characterisation of the spectrum of population health risks is needed to guide public heath responses to severe smoke events as this exposure becomes increasingly common with global climate change

Gait initiation in older people—Time to first lateral movement may be the measure of choice

AIMS There are few empirical data to guide the choice of a gait initiation (GI) measure in older people. We investigated the statistical characteristics of the components of GI, their inter-relationships and associations with sensorimotor variables, and the effect on them of cognitive interference. METHODS GI was measured for randomly selected participants aged 60-86 years using a force-platform with and without a cognitive interference task. Sensorimotor measures were obtained using the physiological profile assessment (PPA), and cognitive speed using the digit symbol and symbol search tests. GI was divided into its three components: time to first lateral movement (FLM); transfer time; and swing time. Six summary indices were assessed for suitability. Regression techniques and Spearman correlations were used to examine learning effects, inter-relationships between components, associations with other study factors and responsiveness to cognitive interference. RESULTS The median of trials per participant was the best summary index. Learning effects were observed under single and particularly dual-tasking. Time to FLM was most consistently associated with age, height, weight, sensorimotor variables, falls-risk score and cognitive speed, and was most responsive to dual-tasking. Overall time to GI was more predictive of falls risk than was time to FLM. CONCLUSIONS Multiple trials are recommended for GI component measurement and the median may provide the best summary measure across trials. Time to FLM is the GI component measure of choice in older people due to its relationship with other factors and responsiveness to cognitive interference but without advantage over overall time to GI.

Association between birth weight and adolescent systolic blood pressure in a caucasian birth cohort differs according to skin type, CRH promoter or 11β-HSD2 genotype

Objective: To examine whether the inverse association between birth weight and blood pressure varies by skin pigmentation and/or related genotypes. Study design: 671 children from a predominantly caucasian birth cohort were followed-up to adolescence (mean (SD) age 14.4 (0.64)). Methods: Data on birth weight, socioeconomic status, maternal antenatal smoking, adolescent blood pressure and polymorphisms of candidate genes were obtained and analysed by multiple linear regression. Results: An increase in birth weight of 1 kg was associated with an non-significant difference in adolescent systolic blood pressure of –0.53 mm Hg (95% CI –1.72 to 0.66) per kg after adjustment for child age and cohort entry criteria. The inverse association between birth weight and systolic blood pressure was stronger for those with darker skin (⩾2% melanin) (difference in effect, p = 0.02), those with more copies of the C allele of corticotropin-releasing hormone (CRH) +T1273C (p = 0.06), and those with more copies of the short (⩽236 bp) form of the 11β-HSD2{CA}nrepeat microsatellite (p = 0.03). Conclusions: These findings add to the evidence that cortisol-related pathways may account for at least part of the observed birth weight–blood pressure associations.