Down syndrome in Israel

The incidence of Down syndrome was studied in Jerusalem for the years 1964-1970 showing an overall incidence rate of 2.43 per 1,000 live births. A National Down Syndrome Register was established in 1978 and data on annual incidence and mortality rates from 1979-1997 is presented. The incidence in 1997 was 1.0 per 1,000 live births, but 2.32 per 1,000, when live births and terminated pregnancies are summed. Infant mortality has generally decreased in the past 20 years in Israel, and a decrease in infant mortality in Down syndrome has also been noted. This is due to better medical treatment and increased parental involvement in the care for infants with Down syndrome.     

Language in ageing persons with Down syndrome

Several cross-sectional studies and one longitudinal study were conducted on the language abilities of various cohorts of persons with Down syndrome aged between 14 and 50 years. No significant difference was observed on any of the receptive and productive morphosyntactic and lexical measures used, suggesting no marked change in the language of these persons from adolescence onto late adulthood. Repeated measures of cerebral metabolic rate (CMR) for fluorodeoxyglucose using a Positron Emission Tomography were made over a 4-year interval with 7 participants with Down syndrome aged between 37 and 49 years. A gradual decrease in global CMR for both cerebral hemispheres and for each participant was documented. It was particularly marked for 3 participants. However, no language deterioration could be associated with their marked lowering in CMR.     

Interhemispheric transmission time in persons with Down syndrome

Background The study of cerebral specialization in persons with Down syndrome (DS) has revealed an anomalous pattern of organization. Specifically, persons with DS elicit a right cerebral hemisphere lateralization for receptive language and a left cerebral hemisphere lateralization for the production of simple and complex movements: a pattern quite different from the left hemisphere lateralization typically characterizing the aforementioned processes in the non‐DS population. It is thought that the putative separation between speech perception and movement planning systems as well as the cost of interhemispheric integration impedes verbal‐motor behaviours in persons with DS. Moreover, morphological anomalies of callosal structure may further amplify between‐hemisphere communication difficulties in the DS population. In the present investigation, we employed a behavioural technique (i.e. the Poffenberger paradigm; Poffenberger) to determine whether global anomalies of callosal structure further amplify deficits in interhemispheric communication. Methods Fourteen individuals with DS and 25 chronological age‐matched and gender‐equated participants without intellectual disability performed a visuomotor reaction time (RT) test with their left or right hand to visual stimuli appearing left or right of visual fixation. Typically it is reported that responses to visual stimuli appearing ipsilateral to the responding hand (i.e. the uncrossed condition) are faster than responses wherein visual stimuli and responding hand are contralaterally mapped (i.e. the crossed condition). The increased RT associated with the crossed condition is reported on the order of 4 ms and has been interpreted to reflect the physiological result of interhemispheric transmission. Results Not surprisingly persons with DS exhibited slower and more variable RTs relative to control counterparts. In addition, a reliable RT advantage favouring the uncrossed conditions was observed among control participants but not persons with DS. Conclusions In keeping with the extant literature, RT performance of the DS group was slower and more variable than control counterparts. This finding has been interpreted to reflect an ‘adaptive reaction’ wherein the perceptual‐motor abilities of persons with DS are not optimized to respond to externally paced stimuli. In terms of evaluating interhemispheric transmission via the Poffenberger paradigm, our results show the finite measures of explicit brain–behaviour relations characterizing so‐called healthy controls are not always tenable in the DS population. Indeed, we believe such a finding underpins the aforementioned ‘adaptive reaction’ exemplifying preferred movement control in persons with DS.     

Psychiatric disorders in persons with Down syndrome.

This study was designed to provide information on the prevalence and nature of psychiatric disorders in 497 individuals with Down syndrome. There were 261 patients under 20 years of age and 164 patients 20 years and older, with both groups followed as outpatients, and 72 residents from a state school. The overall frequency of psychiatric disorders in our study population was 22.1%. Patients under 20 years of age often displayed disruptive behaviors, anxiety disorders, and repetitive behaviors. Individuals with Down syndrome 20 years and older who were followed as outpatients more often exhibited major depressive disorders and state school residents were found to have an increased prevalence of dementia.     

Learning motor synergies by persons with Down syndrome

Persons with Down syndrome are frequently described as ‘clumsy’. The recent progress in the development of quantitative approaches to motor synergies has allowed researchers to move towards an understanding of ‘clumsiness’ at the level of underlying control mechanisms. This progress has also offered an opportunity to quantify changes in motor synergies that accompany improvement in the performance of motor tasks. Previous studies of our group have shown, in particular, that persons both with and without Down syndrome are able to show improvements in indices of their multi‐finger synergies in tasks that require accurate production of finger forces. In particular, 3 days of practice has been shown to lead to significant improvements in indices of multi‐finger synergies that stabilize the time patterns of the total force produced by the fingers of a hand. Persons with Down syndrome showed a qualitative change in their synergies that failed to stabilize the total force altogether prior to practice and became able to do so after practice. In addition, the studies have also shown that variable practice is more beneficial for the improvement of motor synergies than blocked practice. I would like to draw an optimistic conclusion that persons with Down syndrome are not inherently ‘clumsy’, but have a vast potential for an improvement of their motor performance. The current state of the area of motor control allows researchers and practitioners to tap into these reserves, and to use quantitative indices of changes in motor synergies with practice to optimize motor performance of these individuals.     

Cancer incidence among persons with fragile X syndrome in Finland: a population-based study

Background   Fragile X syndrome is a common inheritable cause of intellectual disability (ID) and is characterised by a large number of CGG repeats at the gene FMR1 located on the X-chromosome. It has been reported that this genetic mechanism may protect against malignant transformations.
Methods   We extracted from the Finnish registry on persons with ID a cohort of 302 persons with a fragile X diagnosis during 1982–1986. Follow-up for cancer incidence was performed in the Finnish Cancer Registry until the end of the year 2005.
Results   There were 11 reported cancers during the mean follow-up of 21.4 years per person. The expected number of cancers based on the average Finnish population was 13.8 and no statistically significant protective effect was detected [standardised incidence ratios (SIR) 0.80, confidence interval (CI) 95% 0.40–1.4]. An increased risk for lip cancer was found (SIR 23, CI 95% 2.8–85).
Conclusions   Confirmation of hypotheses about the mechanisms linking FXS and cancer needs further research.     

Towards optimal mental health of persons with Down syndrome

This paper outlines the risk of mental health disorders in adults with Down syndrome and considers the practical ways in which positive well-being can be promoted. It emphasises that prevention begins at birth and parents need to be alerted to positive child-rearing strategies from infancy.     

Health co-morbidities in ageing persons with Down syndrome and Alzheimer's dementia

Background Consideration of the relationship between physical and mental health co-morbidities in ageing persons with Down syndrome (DS) and Alzheimer's dementia (AD) is of clinical importance both from a care and resource perspective. Aim To investigate and measure health co-morbidities in ageing persons with Down syndrome with and without AD. Methods Recorded physical and mental health needs were ascertained for 124 persons with DS > 35 years through a systematic and detailed search of individual medical and nursing case records. Differences in persons with and without AD were investigated, by stage of dementia and by level of intellectual disability (ID). A summed score for health co-morbidities was created and compared using t-tests. Results Persons with AD had significantly higher co-morbidity scores than persons without AD (t = −8.992, d.f. = 121, P < 0.0001). There was also a significant difference in summed co-morbidity scores for persons at end-stage vs. persons at mid-stage AD (t = −6.429, d.f. = 56, P < 0.0001). No differences were found by level of ID. Conclusions Increasing health co-morbidities in persons with DS and AD have important implications for care and resources. Appropriate environmental supports combined with competent skilled staff are crucial and will have an important impact on the quality of life for this increasingly at risk population.     

The effect of acetyl-L-carnitine administration on persons with Down syndrome

Since previous investigations reported improvements in cognition of patients with dementia after acetyl-L-carnitine therapy and since there is an increased risk for persons with Down syndrome to develop Alzheimer disease, this study was designed to investigate the effect of acetyl-L-carnitine administration on neurological, intellectual, and social functions in adults with Down syndrome. In this double-blind study we enrolled 40 individuals with Down syndrome and administered acetyl-L-carnitine to the study group during a six months period. Specified examinations and psychological tests were given to persons in both the study and control groups at the start of the investigation and at 3, 6, and 9 months. A detailed analysis of the data revealed that acetyl-L-carnitine administration did not enhance central nervous system functions and that it did not benefit persons with Down syndrome.     

Relinquishment of infants with Down syndrome in Israel: trends by time

To assess factors affecting parental relinquishment of infants with Down syndrome, we conducted a nationwide cohort study of infants with Down syndrome who were born in Israel during 1979-1983 and 1987-1991. Overall relinquishment rate was 25%. Major factors affecting relinquishment were mother's age, birth order, infant's health status, and study periods. A decision to relinquish a newborn infant in the hospital is probably based on a combination of several parameters, such as the economic status of the family, social mores, and religious beliefs.     

Mortality and causes of death in persons with Down syndrome in California

This study investigated mortality and causes of death between 1988 and 1999 in 14781 persons (6702 female) with Down syndrome in California, comparing age, sex, ethnicity, and other factors. Mean age at the start of follow-up was 14 years 8 months (SD 14y 10mo). During the study period 600 persons died. The standardized mortality ratio (SMR) for the population was 5.5. Blacks were at greater risk than whites, Hispanics, or Asians (relative risk = 1.5). Mortality declined during the period, especially for children with congenital heart defects. Leukemia (SMR = 17), respiratory illnesses (SMR = 27), congenital anomalies (SMR = 72), and circulatory diseases (SMR = 5.3) accounted for most of the excess mortality. With the exception of leukemia, cancer mortality was not different from that of the general population.     

Accuracy of a piezoelectric pedometer in persons with and without Down syndrome

BackgroundPiezoelectric pedometers with a tri-axial accelerometer mechanism may effectively monitor physical activity in persons with Down syndrome (DS), but their accuracy has not been determined in this population.AimTo examine the accuracy of a pedometer with a tri-axial accelerometer mechanism in measuring steps at different walking speeds in persons with and without DS.MethodsEighteen persons with DS (8 women; age 25 ± 7 y) and 22 persons without DS (9 women; 26 ± 5 y) participated in this study. Participants completed six over-ground walking trials at the preferred speed and at 0.5, 0.75, 1.0, 1.25, and 1.5 m s⁻¹, each lasting 6 min. The steps taken were measured with hand-tally and with the Walk4Life MVPa piezoelectric pedometer. Pedometer accuracy was assessed with absolute percent error and Bland-Altman plots.ResultsAbsolute percent error did not differ between persons with and without DS across speeds. Error decreased with increased speed (p < 0.001), but leveled off at ≥1.0 m s⁻¹. Pedometers underestimated steps at 0.5 and 0.75 m s⁻¹, but were highly accurate at the preferred walking speed and at speeds ≥1.0 m s⁻¹.ConclusionsA piezoelectric pedometer with a tri-axial accelerometer mechanism measures steps with high accuracy at the preferred walking speed and at speeds ≥1.0 m s⁻¹ in persons with and without DS. Accuracy, however, is compromised at slower speeds. Across speeds, pedometer error is similar between persons with and without DS.     

Fractal scaling properties of heart rate dynamics in persons with Down syndrome

It has been shown that the fractal scaling properties of heart rate dynamics, in healthy aging, differ from that seen in heart disease and this favors the use of fluctuation measures as diagnostic tools. The purpose of this study was to evaluate the fractal heart rate dynamics in adults with Down syndrome (DS) under different physiological conditions (rest, exercise and post-exercise recovery) and compare their responses with those of nondisabled individuals. Fourteen participants (10 males; and 4 females) with DS and 13 nondisabled (9 males, and 4 females) controls performed maximal and submaximal treadmill tests with metabolic and heart rate measurements. Detrended fluctuation analysis was performed on the last 256 consecutive R-R intervals obtained under the following conditions: (1) standing rest, (2) submaximal treadmill exercise and (3) standing post-exercise recovery. Participants with DS presented lower chronotropic response than controls to peak and submaximal exercise (p<0.05). The short-term scaling exponent (α(1)) was greater in the DS group at rest (1.29±0.06 vs 1.07±0.08), during exercise (1.24±0.09 vs 0.99±0.08) and recovery (1.31±0.06 vs 1.21±0.06) (p<0.05). Furthermore, the fractal scaling distance score (I1-α(1)I) of participants with DS was also greater than that of controls under each physiological condition (p<0.05). This confirmed their greater fractal distance from the healthy value of 1.0. In conclusion, adults with DS show a breakdown of scale-invariant organization in heart rate dynamics towards Brownian noise and this is similar to that described in healthy aging.     

Predicting METs from the heart rate index in persons with Down syndrome

Persons with Down syndrome (DS) have altered heart rate modulation and very low aerobic fitness. These attributes may impact the relationship between metabolic equivalent units (METs) and the heart rate index (HR_index—the ratio between heart rate during activity and resting heart rate), thereby altering the HR_index thresholds for moderate- and vigorous-intensity physical activity. This study examined whether the relationship between METs and HR_index differs between persons with and without DS and attempted to develop thresholds for activity intensity based on the HR_index for persons with DS. METs were measured with portable spirometry and heart rate with a monitor in 18 persons with DS (25 ± 7 years; 10 women) and 18 persons without DS (26 ± 5 years; 10 women) during 6 over-ground walking trials, each lasting 6 min, at the preferred walking speed and at 0.5, 0.75, 1.0, 1.25, and 1.5 m/s. The relationship between METs and HR_index in the two groups was analyzed with multi-level modeling with random intercepts and slopes. Group, HR_index, and the square of HR_index were significant predictors of METs (p < 0.001; R² = 0.65). Absolute percent error did not differ significantly between groups across speeds (DS: 19.6 ± 14.4%; non-DS: 21.0 ± 14.5%). Bland–Altman plots demonstrated somewhat greater variability in the difference between actual and predicted METs in participants with than without DS. The HR_index threshold for moderate-intensity activity was 1.32 and 1.20 for persons with and without DS, respectively. The HR_index threshold for vigorous-intensity activity was 1.80 and 1.65 for persons with and without DS, respectively. Persons with DS have an altered relationship between METs and HR_index and higher HR_index thresholds for moderate- and vigorous-intensity physical activity.     

Arterial stiffness response to exercise in persons with and without Down syndrome

This study compared arterial stiffness and wave reflection at rest and following maximal exercise between individuals with and without Down syndrome (DS), and the influence of body mass index (BMI), peak oxygen uptake (VO₂peak) on changes in arterial stiffness. Twelve people with DS (26.6 ± 2.6 yr) and 15 healthy controls (26.2 ± 0.6 yr) completed this study. Intima-media thickness (IMT) and stiffness of common carotid artery was examined. Hemodynamic and arterial variables were measured before and 3-min after exercise. Persons with DS had higher BMI and lower VO₂peak than controls. IMT did not differ between groups. At rest, carotid β stiffness was significantly higher in persons with DS (P < 0.05) but there was no difference in between groups for any of the other arterial stiffness measures. After exercise, persons with DS exhibited attenuated arterial stiffness responses in AIx-75, carotid β stiffness and Ep in contrast with controls (significant group-by-time interactions). When controlling for BMI and VO₂peak, the interactions disappeared. In both groups combined, BMI was correlated significantly with carotid Ep and β at rest. VO₂peak correlated significantly with AIx-75 and its pre-post change (r = ?0.45, P = 0.029; r = 0.47, P = 0.033, respectively). The arterial stiffness responses to maximal exercise in persons with DS were blunted, potentially reflecting diminished vascular reserve. Obesity and particularly VO₂peak influenced these findings. These results suggest impaired vascular function in people with DS.     

Heart rate complexity in response to upright tilt in persons with Down syndrome

People with Down syndrome (DS) show altered autonomic response to sympatho-excitation. Cardiac autonomic modulation may be examined with heart rate (HR) complexity which is associated uniquely with cardiovascular risk. This study examined whether the response of HR complexity to passive upright tilt differs between persons with and without DS and whether potential between-group differences in this response are accounted for by differences in body mass index (BMI). The electrocardiogram of 16 persons with DS (8 women, 8 men) and 16 persons without DS (8 women, 8 men) was recorded during 10 min of supine rest and 10 min of upright tilt. For each participant, 550 continuous, steady state, and ectopy-free R-R intervals under each condition were analyzed. Dependent variables were approximate entropy, correlation dimension, StatAv, and the mean R-R interval. In response to tilt, changes in approximate entropy and correlation dimension were reduced in participants with DS (p<0.05). These differences were explained by higher BMI in participants with DS. StatAv increased in persons with DS (p < 0.05) and stayed the same in those without DS even when controlling for BMI. The response of R-R interval did not differ between groups. None of the variables differed between groups at rest. Therefore, people with DS show smaller decrease in HR complexity in response to upright tilt than people without DS partially due to their higher BMI. Resting HR complexity does not differ between persons with and without DS. These results may have implications for cardiovascular risk in people with DS.     

The profile and incidence of cancer in Down syndrome

Background Down syndrome is one of the commonest causes of intellectual disability. As life expectancy improves with early and more intensive surgical and medical treatments, people with the disorder are more likely to exhibit classic morbidity and mortality patterns and be diagnosed with diseases such as cancer. Methods A profile of cancer cases among people with Down syndrome has been compiled, based on the analysis of a linked data set that included information from the Disability Services Commission of Western Australian and the State Cancer Registry. Results and conclusions Although the total age‐ and sex‐standardized incidence ratios (SIRs) for people with Down syndrome were similar to that for the general population, SIRs for leukaemia were significantly higher while the incidence of certain other types of cancers was reduced. Overall, there was a lower incidence of solid tumours in Down syndrome, possibly reflecting the age profile of the study cohort.