Evaluation of movement speed and reaction time as predictors of all-cause mortality in men

Associations of healthy aging index and all-cause and cause-specific mortality: a prospective cohort study of UK Biobank participants

The healthy aging index (HAI) has been recently developed as a surrogate measure of biological age. However, to what extent the HAI is associated with all-cause and cause-specific mortality and whether this association differs in younger and older adults remains unknown. We aimed to quantify the association between the HAI and mortality in a population of UK adults. In the prospective cohort study, data are obtained from the UK Biobank. Five HAI components (systolic blood pressure, reaction time, cystatin C, serum glucose, forced vital capacity) were scored 0 (healthiest), 1, and 2 (unhealthiest) according to sex-specific tertiles or clinically relevant cut-points and summed to construct the HAI (range 0-10). Cox proportional hazard regression models were used to estimate the associations of the HAI with the risk of all-cause and cause-specific mortality. 387,794 middle-aged and older participants were followed up for a median of 8.9 years (IQR 8.3-9.5). A total of 14,112 all-cause deaths were documented. After adjustments, each 1-point increase in the HAI was related to a higher risk of all-cause mortality (hazards ratio [HR], 1.17; 95%CI, 1.15-1.18). Such association was stronger among adults younger than 60 years (1.19, 1.17-1.21) than that among those 60 years and older (1.15, 1.14-1.17) (P interaction < 0.001). For each unit increment of the HAI, the multivariate-adjusted HRs for risk of death were 1.28 (1.25-1.31) for cardiovascular diseases, 1.09 (1.07-1.10) for cancer, 1.36 (1.29-1.44) for digestive disease, 1.42 (1.35-1.48) for respiratory disease, 1.42 (1.33-1.51) for infectious diseases, and 1.15 (1.09-1.21) for neurodegenerative disease, respectively. Our findings indicate that the HAI is positively associated with all-cause and cause-specific mortality independent of chronological age. Our results further underscore the importance of effective early-life interventions to slow aging and prevent premature death.

Comparing neuromotor functions in 45- and 65-year-old adults with 18-year-old adolescents

Aim

This cross-sectional analysis investigates how neuromotor functions of two independent cohorts of approximately 45- and 65-year-old individuals are different from 18-year-old adolescents using the Zurich Neuromotor Assessment-2 (ZNA-2).

Methods

A total of 186 individuals of the Zurich Longitudinal Studies (ZLS) born in the 1950s (mean age 65.1 years, SD = 1.2 year, range of ages 59.0-67.5 years, n = 151, 82 males) and 1970s (mean age 43.6 years, SD = 1.3 year, range of ages 40.8-46.6 years, n = 35, 16 males) were tested with the ZNA-2 on 14 motor tasks combined in 5 motor components: fine motor, pure motor, balance, gross motor, and associated movements. Motor performance measures were converted into standard deviation scores (SDSs) using the normative data for 18-year-old individuals as reference.

Results

The motor performance of the 45-year-old individuals was remarkably similar to that of the 18-year-olds (SDS from -0.22 to 0.25) apart from associated movements (-0.49 SDS). The 65-year-olds showed lower performance than the 18-year-olds in all components of the ZNA-2, with the smallest difference observed for associated movements (-0.67 SDS) and the largest for gross motor skills (-2.29 SDS). Higher body mass index (BMI) was associated with better performance on gross motor skills for 45-year-olds but with worse performance for 65-year-olds. More educational years had positive effects on gross motor skills for both ages.

Interpretation

With the exception of associated movements, neuromotor functions as measured with the ZNA-2 are very similar in 45- and 18-year-olds. In contrast, at age 65 years, all neuromotor components show significantly lower function than the norm population at 18 years. Some evidence was found for the last-in-first-out hypothesis: the functions that developed later during adolescence, associated movements and gross motor skills, were the most vulnerable to age-related decline.

Age-related changes in mobility assessments correlate with repetitive goal-directed arm-movement performance

BACKGROUND

There is ample evidence that mobility abilities between healthy young and elderly people differ. However, we do not know whether these differences are based on different lower leg motor capacity or instead reveal a general motor condition that could be detected by monitoring upper-limb motor behavior. We therefore captured body movements during a standard mobility task, namely the Timed Up and Go test (TUG) with subjects following different instructions while performing a rapid, repetitive goal-directed arm-movement test (arm-movement test). We hypothesized that we would be able to predict gait-related parameters from arm motor behavior, even regardless of age.

METHODS

Sixty healthy individuals were assigned to three groups (young: mean 26 ± 3 years, middle-aged 48 ± 9, old 68 ± 7). They performed the arm-movement and TUG test under three conditions: preferred (at preferred movement speed), dual-task (while counting backwards), and fast (at fast movement speed). We recorded the number of contacts within 20 s and the TUG duration. We also extracted TUG walking sequences to analyze spatiotemporal gait parameters and evaluated the correlation between arm-movement and TUG results.

RESULTS

The TUG condition at preferred speed revealed differences in gait speed and step length only between young and old, while dual-task and fast execution increased performance differences significantly among all 3 groups. Our old group's gait speed decreased the most doing the dual-task, while the young group's gait speed increased the most during the fast condition. As in our TUG results, arm-movements were significant faster in young than in middle-aged and old. We observed significant correlations between arm movements and the fast TUG condition, and that the number of contacts closely predicts TUG timefast and gait speedfast. This prediction is more accurate when including age.

CONCLUSION

We found that the age-related decline in mobility performance that TUG reveals strongly depends on the test instruction: the dual-task and fast condition clearly strengthened group contrasts. Interestingly, a fast TUG performance was predictable by the performance in a fast repetitive goal-directed arm-movements test, even beyond the age effect. We assume that arm movements and the fast TUG condition reflect similarly reduced motor function.

TRIAL REGISTRATION

German Clinical Trials Register (DRKS) number: DRKS00016999, prospectively registered on March, 26, 2019.

From thinking fast to moving fast: motor control of fast limb movements in healthy individuals

The ability to produce high movement speeds is a crucial factor in human motor performance, from the skilled athlete to someone avoiding a fall. Despite this relevance, there remains a lack of both an integrative brain-to-behavior analysis of these movements and applied studies linking the known dependence on open-loop, central control mechanisms of these movements to their real-world implications, whether in the sports, performance arts, or occupational setting. In this review, we cover factors associated with the planning and performance of fast limb movements, from the generation of the motor command in the brain to the observed motor output. At each level (supraspinal, peripheral, and motor output), the influencing factors are presented and the changes brought by training and fatigue are discussed. The existing evidence of more applied studies relevant to practical aspects of human performance is also discussed. Inconsistencies in the existing literature both in the definitions and findings are highlighted, along with suggestions for further studies on the topic of fast limb movement control. The current heterogeneity in what is considered a fast movement and in experimental protocols makes it difficult to compare findings in the existing literature. We identified the role of the cerebellum in movement prediction and of surround inhibition in motor slowing, as well as the effects of fatigue and training on central motor control, as possible avenues for further research, especially in performance-driven populations.

Effect of Video Observation and Motor Imagery on Simple Reaction Time in Cadet Pilots

Neuromotor training can improve motor performance in athletes and patients. However, few data are available about their effect on reaction time (RT). We investigated the influence of video observation/motor imagery (VO/MI) on simple RT to visual and auditory stimuli. The experimental group comprised 21 cadets who performed VO/MI training over 4 weeks. Nineteen cadets completed a sham intervention as control. The main outcome measure was RT to auditory and visual stimuli for the upper and lower limbs. The RT to auditory stimuli improved significantly post-intervention in both groups (control vs. experimental mean change for upper limbs: -40 ms vs. -40 ms, p = 0.0008; for lower limbs: -50 ms vs. -30 ms, p = 0.0174). A trend towards reduced RT to visual stimuli was observed (for upper limbs: -30 ms vs. -20 ms, p = 0.0876; for lower limbs: -30 ms vs. -20 ms, p = 0.0675). The interaction term was not significant. Only the specific VO/MI training produced a linear correlation between the improvement in the RT to auditory and visual stimuli for the upper (r = 0.703) and lower limbs (r = 0.473). In conclusion, VO/MI training does not improve RT when compared to control, but it may be useful in individuals who need to simultaneously develop a fast response to different types of stimuli.

Sex differences in body composition but not neuromuscular function following long-term, doxycycline-induced reduction in circulating levels of myostatin in mice

Age-related declines in muscle function result from changes in muscle structure and contractile properties, as well as from neural adaptations. Blocking myostatin to drive muscle growth is one potential therapeutic approach. While the effects of myostatin depletion on muscle characteristics are well established, we have very little understanding of its effects on the neural system. Here we assess the effects of long-term, post-developmental myostatin reduction on electrophysiological motor unit characteristics and body composition in aging mice. We used male (N = 21) and female (N = 26) mice containing a tetracycline-inducible system to delete the myostatin gene in skeletal muscle. Starting at 12 months of age, half of the mice were administered doxycycline (tetracycline) through their chow for one year. During that time we measured food intake, body composition, and hindlimb electromyographic responses. Doxycycline-induced myostatin reduction had no effect on motor unit properties for either sex, though significant age-dependent declines in motor unit number occurred in all mice. However, treatment with doxycycline induced different changes in body composition between sexes. All female mice increased in total, lean and fat mass, but doxycycline-treated female mice experienced a significantly larger increase in lean mass than controls. All male mice also increased total and lean mass, but administration of doxycycline had no effect. Additionally, doxycycline-treated male mice maintained their fat mass at baseline levels, while the control group experienced a significant increase from baseline and compared to the doxycycline treated group. Our results show that long-term administration of doxycycline results in body composition adaptations that are distinctive between male and female mice, and that the effects of myostatin reduction are most pronounced during the first three months of treatment. We also report that age-related changes in motor unit number are not offset by reduced myostatin levels, despite increased lean mass exhibited by female mice.

Potentials of Smart dynamometer use for clinical and self-management of rehabilitation in breast cancer survivors: a feasibility study

The aim of this study was to examine the feasibility of the Smart dynamometer as a rehabilitation exercise device in a daily care by comparing with the existing medical devices. We used and analyzed clinical and measurement data of breast cancer survivors who have used Smart dynamometer during their rehabilitation after breast cancer surgery. The Smart dynamometer was compared with the two existing devices of Takei dynamometer and surface electromyography (sEMG) that were used in routine care, respectively. Three key components of the rehabilitation exercise devices were analyzed to validate the feasibility of the Smart dynamometer: grip strength, reaction time, and grip endurance time. Pearson's correlation analysis was performed to compare the statistical significance between the devices. The data of 12 and 15 female breast cancer patients were analyzed for comparing the Smart dynamometer with Takei dynamometer and sEMG, respectively. There was a very weak correlation between the maximum values from the Takei and the Smart dynamometers in the affected and non-affected arms of breast cancer patients (r = 0.5321, 0.4733). Comparisons of 3 features between the Smart dynamometer and sEMG showed that there were strong positive correlations for both reaction time and endurance time in the affected and non-affected arms (r > 0.9). The feasibility of the Smart dynamometer for the possible use in a daily rehabilitation exercise was partially verified. Moreover, since the Smart dynamometer was highly correlated with time-related variables, it was important and significant to measure both grip strength and time-related information.

Reaction times match IQ for major causes of mortality: Evidence from a population based prospective cohort study

Introduction

The association of premorbid cognitive ability with all-cause mortality is now well established. However, since all-cause mortality is relatively uninformative about aetiology, evidence has been sought, and is beginning to accumulate, for associations with specific causes of mortality. Likewise, the underlying causal pathways may be illuminated by considering associations with different measures of cognitive ability. For example, critics of IQ type measures point to possible cultural or social biases and there is, consequently, a need for more culturally neutral measures such as reaction times. We examine the associations of cognitive ability with major causes of mortality, including: cardiovascular disease, cancer and respiratory disease and compare the results for a standard IQ test, the Alice Heim 4 (AH4), with those for simple and four-choice reaction times.

Methods

Data were derived from the oldest cohort of the West of Scotland Twenty-07 Study. Participants were randomly sampled from the Central Clydeside Conurbation, a mainly urban area centred on Glasgow city. At baseline, aged 56, they were interviewed in their homes by trained interviewers; the AH4 was administered and reaction times measured using a portable electronic device. Vital status was ascertained via linkage to the NHS central register. Cox regression was used in SAS 9.4 for the main analyses. Adjustments were made for sex, smoking status and social class.

Results

Full data on AH4, RT and covariates were available for 1350 out of 1551. During 29 years of follow-up, there were 833 deaths: 279 cardiovascular disease (CVD) (168 CHD; 68 stroke); 291 cancer; 97 respiratory disease; 42 digestive disease; and 39 dementia. The 85 remaining deaths were a heterogeneous mixture with no cause accounting for more than 14.

AH4 scores were associated with most major causes. Digestive disease and dementia had similar effect sizes but were not significant. Within cardiovascular disease, there was an association with coronary heart disease but not stroke. The association with cancer was primarily due to those cancers related to smoking.

RT measures were mostly associated with the same causes of death. Where significant, effects were in the same directions and of similar magnitude. That is, lower AH4 scores, longer reaction times, and more variable reaction times were all associated with increased mortality risk from the major causes of death. A summary measure of RT outperformed the AH4 for most causes.

Conclusion

The association between intelligence with mortality from the major causes is also seen with reaction times. That effect sizes are of similar magnitude is suggestive of a common cause. It also implies that the association of cognitive ability with mortality is unlikely to be due to any social, cultural or educational biases that are sometimes ascribed to intelligence measures.

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Intelligence and reaction times are both associated with most major causes of mortality

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Effect sizes are of similar magnitude

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A summary RT measure provides the more parsimonious explanation for most causes

Within-session and one-week practice effects on a motor task in amnestic mild cognitive impairment

Practice effects on neuropsychological tests, which are improvements in test scores due to repeated exposure to testing materials, are robust in healthy elders, but muted in older adults with cognitive disorders. Conversely, few studies have investigated practice effects on motor tasks involving procedural memory, particularly across test-retest periods exceeding 24 hours. The current study examined one-week practice effects on a novel upper extremity motor task in 54 older adults with amnestic mild cognitive impairment. Results indicate that these individuals with primary memory deficits did improve on this motor task within a brief training session as well as across one week. These practice effects were unrelated to demographic characteristics or global cognition. One-week practice effects were, however, negatively related to delayed memory function, with larger practice effects being associated with poorer delayed memory and potentially better visuospatial ability. The presence of longer term practice effects on a procedural motor task not only has implications for how longitudinal assessments with similar measures involving implicit memory might be interpreted, but may also inform future rehabilitative strategies for patients with more severe declarative memory deficits.

Response abilities of children with Down Syndrome and other intellectual developmental disorders

Efficiency with which a task is performed results from the precise timing and force with which the task is executed. We aimed at assessing the influence of change in task constructs on the response abilities of children who are known to have impaired perceptual motor control. To answer this question, we assessed the response abilities in terms of response time(RT) and response force(RF) among children with Down Syndrome(DS), intellectual developmental disorders(IDD) and those who are typically developing. A response analyzer was used to assess their response abilities across a variety of task constructs namely while performing a simple response task, dual task (i.e. passive and active dual tasks), force modulation task and choice response task. Across all tasks, it was seen that their RT increased while RF decreased as the tasks became more complex in nature. The number of participants in the DS and IDD group diminished as the task complexity increased, reflecting their inherent difficulty in learning new tasks and executing a common expected response under different task conditions. The response abilities of the DS and IDD group was comparable across tasks and varied significantly from the TDC group. The study enables us to understand the influence of task difficulties on the response abilities and participation across groups of children with and without disabilities. The results of the study necessitate the need to evaluate and find methods to train the response abilities of children with DS and IDD, which has considerable implications towards the performance of their daily life skills.

Association Between Hospital Readmission and Acute and Sustained Delays in Functional Recovery During 18 Months After Elective Surgery: The Successful Aging after Elective Surgery Study

OBJECTIVES

To examine the effect of hospital readmission on functional recovery after elective surgery in older adults.

DESIGN

Prospective cohort of individuals aged 70 and older undergoing elective surgery, enrolled from June 2010 to August 2013.

SETTING

Two academic medical centers.

PARTICIPANTS

Community-dwelling older adults (N = 566; mean age ± standard deviation 77 ± 5) undergoing major elective surgery and expected to be admitted for at least 3 days.

MEASUREMENTS

Readmission was assessed in multiple interviews with participants and family members over 18 months and validated against medical record review. Physical function was assessed according to ability to perform instrumental activities of daily living (IADLs) and activities of daily living (ADL), Medical Outcomes Study 12-item Short-Form Survey Physical Component Summary score, and a standardized functional composite.

RESULTS

Two hundred fifty-five (45%) participants experienced 503 readmissions. Readmissions were associated with delays in functional recovery in all measures of physical function. Having two or more readmissions over 18 months was associated with persistent and significantly greater risk of IADL dependence (relative risk (RR) = 1.8, 95% confidence interval (CI) = 1.5-2.3) and ADL dependence (RR = 3.3, 95% CI = 1.7-6.4). Degree of functional impairment increased progressively with number of readmissions. Readmissions within 2 months resulted in delayed functional recovery to baseline by 18 months, and readmissions between 12 and 18 months after surgery resulted in loss of functional recovery previously achieved.

CONCLUSION

Readmission after elective surgery may contribute to delays in functional recovery and persistent functional deficits in older adults.

The Effect of Neurobehavioral Test Performance on the All-Cause Mortality among US Population

Evidence of the association between global cognitive function and mortality is much, but whether specific cognitive function is related to mortality is unclear. To address the paucity of knowledge on younger populations in the US, we analyzed the association between specific cognitive function and mortality in young and middle-aged adults. We analyzed data from 5,144 men and women between 20 and 59 years of age in the Third National Health and Nutrition Examination Survey (1988-94) with mortality follow-up evaluation through 2006. Cognitive function tests, including assessments of executive function/processing speed (symbol digit substitution) and learning recall/short-term memory (serial digit learning), were performed. All-cause mortality was the outcome of interest. After adjusting for multiple variables, total mortality was significantly higher in males with poorer executive function/processing speed (hazard ratio (HR) 2.02; 95% confidence interval 1.36 to 2.99) and poorer recall/short-term memory (HR 1.47; 95% confidence interval 1.02 to 2.12). After adjusting for multiple variables, the mortality risk did not significantly increase among the females in these two cognitive tests groups. In this sample of the US population, poorer executive function/processing speed and poorer learning recall/short-term memory were significantly associated with increased mortality rates, especially in males. This study highlights the notion that poorer specific cognitive function predicts all-cause mortality in young and middle-aged males.

Effects of Short-Term Physical Activity Interventions on Simple and Choice Response Times

Objective. Response time (RT) is important for health and human performance and provides insight into cognitive processes. It deteriorates with age, is associated with chronic physical activity (PA), and improves with PA interventions. We investigated associations between the amount and type of PA undertaken and the rate of change in RT for low-active adults across the age range 18–63 yr. Methods. Insufficiently active adults were assigned to either a walking (n = 263) or higher-intensity (n = 380) exercise program conducted over 40 days. Active controls were also recruited (n = 135). Simple response time (SRT) and choice response time (CRT) were measured before and after the intervention and at 3-, 6-, and 12-month follow-up. Results. SRT and CRT slowed across the age range; however, habitually active participants at baseline had significantly faster CRT (p < 0.05). The interventions increased weekly PA with corresponding increases in physical fitness. These changes were mirrored in faster CRT across the study for both intervention groups (p < 0.05). No changes were found for SRT. Conclusions. Both PA interventions resulted in improvements in CRT among adults starting from a low activity base. These improvements were relatively rapid and occurred in both interventions despite large differences in exercise volume, type, and intensity. There were no effects on SRT in either intervention.

Age-related differences in muscle recruitment and reaction-time performance

Previously, we showed that prolonged reaction-time (RT) in older persons is related to increased antagonist muscle co-activation, occurring already before movement onset. Here, we studied whether a difference in temporal agonist and antagonist muscle activation exists between young and older persons during an RT-test. We studied Mm. Biceps (antagonist muscle) & Triceps (agonist muscle) Brachii activation time by sEMG in 60 young (26 ± 3 years) and 64 older (80 ± 6 years) community-dwelling subjects during a simple point-to-point RT-test (moving a finger using standardized elbow-extension from one pushbutton to another following a visual stimulus). RT was divided in pre-movement-time (PMT, time for stimulus processing) and movement-time (MT, time for motor response completion). Muscle activation time 1) following stimulus onset (PMAT) and 2) before movement onset (MAT) was calculated. PMAT for both muscles was significantly longer for the older subjects compared to the young (258 ± 53 ms versus 224 ± 37 ms, p=0.042 for Biceps and 280 ± 70 ms versus 218 ± 43 ms for Triceps, p<0.01). Longer agonist muscle PMAT was significantly related to worse PMT and RT in young (respectively r=0.76 & r=0.68, p<0.001) and elderly (respectively r=0.42 & r=0.40, p=0.001). In the older subjects we also found that the antagonist muscle activated significantly earlier than the agonist muscle (-22 ± 55 ms, p=0.003). We conclude that in older persons, besides the previously reported increased antagonist muscle co-activation, the muscle firing sequence is also profoundly altered. This is characterized by a delayed muscle activation following stimulus onset, and a significantly earlier recruitment of the antagonist muscle before movement onset.

Age and grip strength predict hand dexterity in adults

In the scientific literature, there is much evidence of a relationship between age and dexterity, where increased age is related to slower, less nimble and less smooth, less coordinated and less controlled performances. While some suggest that the relationship is a direct consequence of reduced muscle strength associated to increased age, there is a lack of research that has systematically investigated the relationships between age, strength and hand dexterity. Therefore, the aim of this study was to examine the associations between age, grip strength and dexterity. 107 adults (range 18-93 years) completed a series of hand dexterity tasks (i.e. steadiness, line tracking, aiming, and tapping) and a test of maximal grip strength. We performed three phases of analyses. Firstly, we evaluated the simple relationships between pairs of variables; replicating the existing literature; and found significant relationships of increased age and reduced strength; increased age and reduced dexterity, and; reduced strength and reduced dexterity. Secondly, we used standard Multiple Regression (MR) models to determine which of the age and strength factors accounted for the greater variance in dexterity. The results showed that both age and strength made significant contributions to the data variance, but that age explained more of the variance in steadiness and line tracking dexterity, whereas strength explained more of the variance in aiming and tapping dexterity. In a third phase of analysis, we used MR analyses to show an interaction between age and strength on steadiness hand dexterity. Simple Slopes post-hoc analyses showed that the interaction was explained by the middle to older aged adults showing a relationship between reduced strength and reduced hand steadiness, whereas younger aged adults showed no relationship between strength and steadiness hand dexterity. The results are discussed in terms of how age and grip strength predict different types of hand dexterity in adults.

Correlations of psycho-physiological parameters influencing the physical fitness of aged women

Regular assessment of psycho-physiological parameters in aged subjects helps to clarify physical and mental conditions which are important in the prevention of health-endangering events to assure a healthy aging. Thirty older care female residents consented voluntarily to participate in the study. The somatic and psycho-physiological parameters recorded were handgrip force, disjunctive reaction time, balance control and whole body movement coordination, the electrocardiogram and heart rate variability. Significant correlations were found between (a) reaction time and balance control efficiency (r = -0.567, p < 0.009), (b) reaction time and movement coordination accuracy (r = -0.453, p < 0.045), (c) cardiac state and movement coordination accuracy (r = 0.545, p < 0.016), (d) cardiac stress and cardiac state (r = -0.495, p < 0.031), and (e) cardiac stress and force (r = -0.822, p < 0.045). In conclusion, for the aim of establishing basic battery tests for assessing psycho-physiological condition of physical fitness our results emphasize the importance of systematic physical activity, endurance and strength training supporting muscle force, balance control and whole-body movement coordination, in addition to improving the cardiac stress index level. The strong interrelation among these parameters allows the drawing of a more complete view regarding the health condition of aged individuals.

Reaction time and mortality from the major causes of death: the NHANES-III study

OBJECTIVE

Studies examining the relation of information processing speed, as measured by reaction time, with mortality are scarce. We explored these associations in a representative sample of the US population.

METHODS

Participants were 5,134 adults (2,342 men) aged 20-59 years from the Third National Health and Nutrition Examination Survey (NHANES III, 1988-94).

RESULTS

Adjusted for age, sex, and ethnic minority status, a 1 SD slower reaction time was associated with a raised risk of mortality from all-causes (HR = 1.25, 95% CI 1.12, 1.39) and cardiovascular disease (CVD) (HR = 1.36, 95% CI 1.17, 1.58). Having 1 SD more variable reaction time was also associated with greater risk of all-cause (HR = 1.36, 95% CI 1.19, 1.55) and CVD (HR = 1.50, 95% CI 1.33, 1.70) mortality. No associations were observed for cancer mortality. The magnitude of the relationships was comparable in size to established risk factors in this dataset, such as smoking.

INTERPRETATION

Alongside better-established risk factors, reaction time is associated with increased risk of premature death and cardiovascular disease. It is a candidate risk factor for all-cause and cause-specific mortality.

Markers of human skeletal muscle mitochondrial biogenesis and quality control: effects of age and aerobic exercise training

Perturbations in mitochondrial health may foster age-related losses of aerobic capacity (VO2peak) and skeletal muscle size. However, limited data exist regarding mitochondrial dynamics in aging human skeletal muscle and the influence of exercise. The purpose of this study was to examine proteins regulating mitochondrial biogenesis and dynamics, VO2peak, and skeletal muscle size before and after aerobic exercise training in young men (20 ± 1 y) and older men (74 ± 3 y). Exercise-induced skeletal muscle hypertrophy occurred independent of age, whereas the improvement in VO2peak was more pronounced in young men. Aerobic exercise training increased proteins involved with mitochondrial biogenesis, fusion, and fission, independent of age. This is the first study to examine pathways of mitochondrial quality control in aging human skeletal muscle with aerobic exercise training. These data indicate normal aging does not influence proteins associated with mitochondrial health or the ability to respond to aerobic exercise training at the mitochondrial and skeletal muscle levels.

Reaction time as a predictor of mortality: the Radiation Effects Research Foundation Adult Health Study

OBJECTIVE

We investigated the association between reaction time (RT) and mortality in middle-aged and older atomic bomb survivors and their unexposed controls over a period of 30 years.

METHODS

During 1970-72, 4912 participants of the Adult Health Study cohort in Hiroshima, Japan, underwent biologic tests including RT. Mortality was followed to the end of 2003.

RESULTS

In a multivariate-adjusted model, the hazard ratio (HR) for 1-standard deviation increments of RT was 1.08 (95% confidence interval [CI]=1.03-1.13) for men, 1.22 (95% CI=1.16-1.28) for women, and 1.13 (95% CI=1.09-1.16) for all. When the analysis was performed by sex, age, and follow-up period, a consistent increase of mortality with increments of RT was observed. The HR for mortality for the highest RT quintile was higher than that of the lowest quintile in all sex-age groups. A significant positive association between mortality risk and RT was observed even after 20 years of follow-up (p=.03 in men, p<.001 in women). RT and radiation dose were risk factors for mortality independent of conventional risk factors such as smoking, high blood pressure, and diabetes mellitus. Interaction between RT and radiation dose had no significant effect on mortality in men. Although increased radiation dose reduced the HR for mortality per RT increment in women, RT and radiation dose were still significant predictors of mortality.

CONCLUSIONS

RT is a consistently strong predictor of mortality. Although mortality risk increased with radiation dose, radiation did not accelerate the relationship between RT and mortality.

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.

The effect of physical fitness training on reaction time in youth with intellectual disabilities

The purpose of this study was to assess whether reaction time in persons with intellectual disabilities can be improved with an exercise program. 50 children and adolescents (M age = 14.7 yr., SD = 1.4, range = 11-18) with mild intellectual disability without Downs syndrome were randomly divided into control (20 boys, 5 girls) and experimental (19 boys, 6 girls) groups. The experimental group participated in a structured physical fitness program for 12 weeks. Reaction time was assessed at baseline and after 12 weeks. Significant improvements in reaction time were observed in the exercise group but not for the control group. Results indicated that reaction time can be improved with an exercise program in youth with intellectual disability.

Adverse events associated with testosterone administration

BACKGROUND

Testosterone supplementation has been shown to increase muscle mass and strength in healthy older men. The safety and efficacy of testosterone treatment in older men who have limitations in mobility have not been studied.

METHODS

Community-dwelling men, 65 years of age or older, with limitations in mobility and a total serum testosterone level of 100 to 350 ng per deciliter (3.5 to 12.1 nmol per liter) or a free serum testosterone level of less than 50 pg per milliliter (173 pmol per liter) were randomly assigned to receive placebo gel or testosterone gel, to be applied daily for 6 months. Adverse events were categorized with the use of the Medical Dictionary for Regulatory Activities classification. The data and safety monitoring board recommended that the trial be discontinued early because there was a significantly higher rate of adverse cardiovascular events in the testosterone group than in the placebo group.

RESULTS

A total of 209 men (mean age, 74 years) were enrolled at the time the trial was terminated. At baseline, there was a high prevalence of hypertension, diabetes, hyperlipidemia, and obesity among the participants. During the course of the study, the testosterone group had higher rates of cardiac, respiratory, and dermatologic events than did the placebo group. A total of 23 subjects in the testosterone group, as compared with 5 in the placebo group, had cardiovascular-related adverse events. The relative risk of a cardiovascular-related adverse event remained constant throughout the 6-month treatment period. As compared with the placebo group, the testosterone group had significantly greater improvements in leg-press and chest-press strength and in stair climbing while carrying a load.

CONCLUSIONS

In this population of older men with limitations in mobility and a high prevalence of chronic disease, the application of a testosterone gel was associated with an increased risk of cardiovascular adverse events. The small size of the trial and the unique population prevent broader inferences from being made about the safety of testosterone therapy. (ClinicalTrials.gov number, NCT00240981.)

Free testosterone levels are associated with mobility limitation and physical performance in community-dwelling men: the Framingham Offspring Study

CONTEXT

Mobility limitation is associated with increased morbidity and mortality. The relationship between circulating testosterone and mobility limitation and physical performance is incompletely understood.

OBJECTIVE

Our objective was to examine cross-sectional and prospective relations between baseline sex hormones and mobility limitations and physical performance in community-dwelling older men.

DESIGN, SETTING, AND PARTICIPANTS

We conducted cross-sectional and longitudinal analyses of 1445 men (mean age 61.0 +/- 9.5 yr) who attended Framingham Offspring Study examinations 7 and 8 (mean 6.6 yr apart). Total testosterone (TT) was measured by liquid chromatography tandem mass spectrometry at examination 7. Cross-sectional and longitudinal analyses of mobility limitation and physical performance were performed with continuous (per SD) and dichotomized [low TT and free testosterone (FT) and high SHBG vs. normal] hormone levels.

MAIN OUTCOME MEASURES

Self-reported mobility limitation, subjective health, usual walking speed, and grip strength were assessed at examinations 7 and 8. Short physical performance battery was performed at examination 7.

RESULTS

Higher continuous FT was positively associated with short physical performance battery score (beta = 0.13; P = 0.008), usual walking speed (beta = 0.02; P = 0.048), and lower risk of poor subjective health [odds ratio (OR) = 0.72; P = 0.01]. In prospective analysis, 1 SD increase in baseline FT was associated with lower risk of developing mobility limitation (OR = 0.78; 95% confidence interval = 0.62-0.97) and progression of mobility limitation (OR = 0.75; 95% confidence interval = 0.60-0.93). Men with low baseline FT had 57% higher odds of reporting incident mobility limitation (P = 0.03) and 68% higher odds of worsening of mobility limitation (P = 0.007).

CONCLUSIONS

Lower levels of baseline FT are associated with a greater risk of incident or worsening mobility limitation in community-dwelling older men. Whether this risk can be reduced with testosterone therapy needs to be determined by randomized trials.

Epidemiology of aging

Over the past century, truly remarkable changes have been observed in the health of older persons throughout the world, and these changes have strongly impacted society. The growth of the older population has resulted mostly from a general increase in the overall population size but is also strongly influenced by major declines in leading causes of mortality. These demographic transformations reverberate in society, increasing medical care and social needs, which are expected to increase steeply in the years to come. Based on demographic and epidemiologic perspectives, these changes were already detectable decades before and should have prompted radical changes in the structure and function of our system of health and social protection at that time. We come to this enormous challenge unprepared.

Age differences in reaction time and attention in a national telephone sample of adults: education, sex, and task complexity matter

This study demonstrated effects of age, education, and sex on complex reaction time in a large national sample (N = 3,616) with a wide range in age (32-85) and education. Participants completed speeded auditory tasks (from the MIDUS [Midlife in the U.S.] Stop and Go Switch Task) by telephone. Complexity ranged from a simple repeated task to an alternating task that involved central executive processes including attention switching and inhibitory control. Increased complexity was associated with slower responses in older adults, those with lower education, and women, even after controlling for differences in health status. Higher levels of education were associated with greater central executive efficiency across adulthood: Overall, adults with college degrees performed on complex tasks like less educated individuals who were 10 years younger, up to age 75. These findings suggest that advanced education can moderate age differences on complex speeded tasks that require central executive processes, at least up to the point in old age at which biological declines predominate. The approach demonstrates the utility of combining laboratory paradigms with survey methods to enable the study of larger, more diverse and representative samples across the lifespan.

ECT generalized seizure drives heart rate above treadmill stress test maximum

OBJECTIVES

Heart rate (HR) accelerates with the electroconvulsive therapy (ECT) seizure and decelerates when it ends. The peak HR during ECT seizure has been reported to reflect clinical impact. We aimed to identify the expected range for ECT peak HR and how it varies with age and sex, as a reference in clinical use.

METHODS

We examined medical records for the maximum peak seizure HR over the ECT course for all ECT patients over defined periods at 2 clinical sites. Methohexital-succinylcholine anesthesia was usually used. Subject totals were 87 men and 90 women.

RESULTS

Electroconvulsive therapy peak HR was 140 to 180 bpm and did not fall with age through 80 years, separately for men and women. A few patients lay outside this cluster and showed age-related decrease. Overall and including the extreme elderly, peak HR fell by 0.29 bpm/yr.

CONCLUSIONS

Electroconvulsive therapy seizure peak HR less than 140 bpm points to weakness of the ECT seizure (and need to increase stimulus dose), cardiac disease, or medication effect limiting HR. Electroconvulsive therapy peak HR exceeds treadmill exercise maximum HR after 60 years and falls significantly less with age than the 0.7 to 1 bpm/yr reported for maximum HR with treadmill exercise stress. These comparisons suggest that ECT peak HR and treadmill maximum HR are limited by different aspects of physiology, and that exercise HR is limited by metabolic demand and humoral activity rather than the heart itself.

Inflammatory factors in age-related muscle wasting

PURPOSE OF REVIEW

This review focuses on recent evidence pointing to the importance of inflammatory factors in the onset and progression of age-related muscle wasting, also known as sarcopenia, and discusses critical areas of uncertainty within the literature that require further development in order to identify novel therapeutics.

RECENT FINDINGS

The research performed in recent years has only strengthened the evidence that inflammatory factors are important in the progression of a catabolic state in muscle wasting. Interactions among various inflammatory cytokines and anabolic factors have been observed, with the balance skewed in favor of catabolism in sarcopenia. Adiposity appears to play an important role in the inflammatory process and possibly the onset of sarcopenia. Inflammatory factors are likely to play an important role in the increased activity of the ubiquitin proteasome, which we argue should be a primary target for the development of molecular therapeutics.

SUMMARY

Future research will need to delve into the molecular interactions that link inflammatory factors and the imbalance between muscle anabolism and catabolism that develops with aging. Identification of specific pathways of importance to sarcopenia will have relevance to a wide range of wasting disorders.