Peter J. Houx

Bio: Peter J. Houx is an academic researcher from Maastricht University. The author has contributed to research in topics: Cognition & Cognitive decline. The author has an hindex of 32, co-authored 47 publications receiving 5123 citations. Previous affiliations of Peter J. Houx include European Graduate School.

Stroop interference: aging effects assessed with the Stroop Color-Word Test.

Abstract: A large, cross-sectional aging investigation of performance on the Stroop Color-Word Test (SCWT) was carried out. Subjects were 247 volunteers, ages 20-80 in seven age levels. Although all subjects thought themselves to be normal and healthy, a post hoc division could be made on the basis of biological life events (BLE). BLE are mild biological or environmental factors, such as repeated experiences of general anesthesia, that can hamper optimal brain functioning. Apart from the anticipated age effects, performance was poorer in subjects who had experienced one or more BLE: The slowing due to BLE was comparable to the effect of age, especially on the task involving language interference in color-naming. Education had a significant effect on performance: More highly educated subjects performed better than less educated subjects. No sex differences were observed. These findings replicate observations made with other tests in parallel studies. They are also in line with several other studies reporting interactions between the effects of aging and physical fitness. This study questions some of the validity of cognitive aging research, as our data suggest that screening for BLE as age-extrinsic factors in nondiseased subjects can reduce many of the performance deficits usually ascribed to aging per se.

The Relation Between Morbidity and Cognitive Performance in a Normal Aging Population

Abstract: Background. Factors related to physical health have been implicated in both normal and pathological aging of cognitive abilities. To substantiate this notion, we studied existing morbidity, as diagnosed by the general practitioner according to well-defined criteria, as a potential predictor of cognitive test performance. Methods. A sample of 1360 individuals, aged 24-81 years and living in the community, was stratified for age, sex, and general ability. Active and total morbidity in this group were classified according to the International Classification of Primary Care. Neurocognitive tests were used to assess the domains of verbal memory, sensorimotor speed, and cognitive flexibility. Results. Multiple regression analyses with adjustment for age, sex, and educational level showed both insulindependent and noninsulin-dependent diabetes to be negatively associated with all cognitive measures. More specific negative associations were found for chronic bronchitis (performance speed) and presbyacusia (memory). Single or aggregated cardiovascular morbidity (including hypertension) was unrelated to test performance. Conclusions. Existing morbidity as a whole contributes only modestly (up to 3.5%) to total variance in cognitive function. However, some specific, relatively common diseases of the elderly, such as diabetes and chronic bronchitis, may aggravate the age-related decline in cognitive ability.

Subjective sleep problems in later life as predictors of cognitive decline. Report from the Maastricht Ageing Study (MAAS)

Abstract: Background Although biological sleep criteria seem to be associated with cognitive changes in older people, it is not clear if subjective sleep parameters are related to cognitive decline in later life. Objectives The aim of this study was to determine whether subjective sleep complaints in a population-based sample of 838 middle aged and older adults (≥ 50 years) predicted cognitive decline over a period of 3 years. Methods Sleep complaints at baseline, assessed with the subscale Sleep Problems of the Symptoms Checklist−90, were used as a predictor variable. Cognitive performance at follow-up, measured with the Mini Mental Status Examination, was employed as a dependent variable. Results Controlling for the effects of age, gender, length of follow-up interval, systemic diseases, and cognitive function at baseline, subjective sleep complaints were negatively associated with cognitive performance at follow-up. Conclusion Subjective sleep complaints predict cognitive decline in middle aged and older adults. Mechanisms behind the effect of subjective sleep complaints on cognitive performance are discussed. Copyright © 2002 John Wiley & Sons, Ltd.

Age-related decline of psychomotor speed- effects of age, brain health, sex, and education

Abstract: A cross-sectional study into age-related decline of psychomotor speed is reported. A newly introduced choice response task was used, involving three conditions: simple reaction time (SRT), choice reaction time (CRT), and CRT with stimulus-response incompatibility. Subjects were 247 volunteers, aged 20 to 80 yr. in seven age levels. Although all subjects thought themselves to be normal and healthy, a post hoc division could be made based on biological life events (BLE, mild biological or environmental factors that can hamper optimal brain functioning, such as repeated general anesthesia). Performance was poorer by subjects who had experienced one or more such event: slowing was comparable to the effect of age, especially in the more difficult task conditions. There were significant effects of sex and education, men being consistently faster than women, and more highly educated subjects performing better than subjects with only low or medium education. These findings replicate observations from other test methods. They are also in line with several other studies giving interactions between the effects of aging and physical fitness. This study questions the validity of much research on aging, as the data suggest that a more rigorous health screening for biological life events in subjects recruited from the normal, healthy population can reduce performance effects normally ascribed to aging. Language: en

Parkinson’s disease: clinical features and diagnosis

Abstract: Objective: Parkinson’s disease (PD) is a progressive neurological disorder characterised by a large number of motor and non-motor features that can impact on function to a variable degree. This review describes the clinical characteristics of PD with emphasis on those features that differentiate the disease from other parkinsonian disorders. Methods: A MedLine search was performed to identify studies that assess the clinical characteristics of PD. Search terms included “Parkinson’s disease”, “diagnosis” and “signs and symptoms”. Results: Because there is no definitive test for the diagnosis of PD, the disease must be diagnosed based on clinical criteria. Rest tremor, bradykinesia, rigidity and loss of postural reflexes are generally considered the cardinal signs of PD. The presence and specific presentation of these features are used to differentiate PD from related parkinsonian disorders. Other clinical features include secondary motor symptoms (eg, hypomimia, dysarthria, dysphagia, sialorrhoea, micrographia, shuffling gait, festination, freezing, dystonia, glabellar reflexes), non-motor symptoms (eg, autonomic dysfunction, cognitive/neurobehavioral abnormalities, sleep disorders and sensory abnormalities such as anosmia, paresthesias and pain). Absence of rest tremor, early occurrence of gait difficulty, postural instability, dementia, hallucinations, and the presence of dysautonomia, ophthalmoparesis, ataxia and other atypical features, coupled with poor or no response to levodopa, suggest diagnoses other than PD. Conclusions: A thorough understanding of the broad spectrum of clinical manifestations of PD is essential to the proper diagnosis of the disease. Genetic mutations or variants, neuroimaging abnormalities and other tests are potential biomarkers that may improve diagnosis and allow the identification of persons at risk.

Delirium in mechanically ventilated patients: validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU).

Abstract: ContextDelirium is a common problem in the intensive care unit (ICU). Accurate diagnosis is limited by the difficulty of communicating with mechanically ventilated patients and by lack of a validated delirium instrument for use in the ICU.ObjectivesTo validate a delirium assessment instrument that uses standardized nonverbal assessments for mechanically ventilated patients and to determine the occurrence rate of delirium in such patients.Design and SettingProspective cohort study testing the Confusion Assessment Method for ICU Patients (CAM-ICU) in the adult medical and coronary ICUs of a US university-based medical center.ParticipantsA total of 111 consecutive patients who were mechanically ventilated were enrolled from February 1, 2000, to July 15, 2000, of whom 96 (86.5%) were evaluable for the development of delirium and 15 (13.5%) were excluded because they remained comatose throughout the investigation.Main Outcome MeasuresOccurrence rate of delirium and sensitivity, specificity, and interrater reliability of delirium assessments using the CAM-ICU, made daily by 2 critical care study nurses, compared with assessments by delirium experts using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria.ResultsA total of 471 daily paired evaluations were completed. Compared with the reference standard for diagnosing delirium, 2 study nurses using the CAM-ICU had sensitivities of 100% and 93%, specificities of 98% and 100%, and high interrater reliability (κ = 0.96; 95% confidence interval, 0.92-0.99). Interrater reliability measures across subgroup comparisons showed κ values of 0.92 for those aged 65 years or older, 0.99 for those with suspected dementia, or 0.94 for those with Acute Physiology and Chronic Health Evaluation II scores at or above the median value of 23 (all P<.001). Comparing sensitivity and specificity between patient subgroups according to age, suspected dementia, or severity of illness showed no significant differences. The mean (SD) CAM-ICU administration time was 2 (1) minutes. Reference standard diagnoses of delirium, stupor, and coma occurred in 25.2%, 21.3%, and 28.5% of all observations, respectively. Delirium occurred in 80 (83.3%) patients during their ICU stay for a mean (SD) of 2.4 (1.6) days. Delirium was even present in 39.5% of alert or easily aroused patient observations by the reference standard and persisted in 10.4% of patients at hospital discharge.ConclusionsDelirium, a complication not currently monitored in the ICU setting, is extremely common in mechanically ventilated patients. The CAM-ICU appears to be rapid, valid, and reliable for diagnosing delirium in the ICU setting and may be a useful instrument for both clinical and research purposes.

Sex Differences in

Abstract: This study suggests that there are sex differences in vocational attitude maturity. In the four-school stratified sample of eleventh grade boys and girls studied, the girls scored significantly higher than the boys in vocational attitude. No sex differences in overall level of self-esteem, as measured by the Tennessee Self-Concept Scale, were found. For both sexes a significant relationship between the over all level of self-esteem and vocational attitude maturity was indicated, with the relationship being higher for males than for females. The self-concept variables of self-satisfaction, family, and moral-ethical self were found to contribute to the vocational attitude maturity of males. For females, the self-concept variables of identity and moral-ethical self contributed to their vocational attitude maturity.

The Adaptive Brain: Aging and Neurocognitive Scaffolding

Abstract: There are declines with age in speed of processing, working memory, inhibitory function, and long-term memory, as well as decreases in brain structure size and white matter integrity. In the face of these decreases, functional imaging studies have demonstrated, somewhat surprisingly, reliable increases in prefrontal activation. To account for these joint phenomena, we propose the scaffolding theory of aging and cognition (STAC). STAC provides an integrative view of the aging mind, suggesting that pervasive increased frontal activation with age is a marker of an adaptive brain that engages in compensatory scaffolding in response to the challenges posed by declining neural structures and function. Scaffolding is a normal process present across the lifespan that involves use and development of complementary, alternative neural circuits to achieve a particular cognitive goal. Scaffolding is protective of cognitive function in the aging brain, and available evidence suggests that the ability to use this mechanism is strengthened by cognitive engagement, exercise, and low levels of default network engagement.