Physical activity and executive functions in the elderly with mild cognitive impairment.

The primary goal of the present study was to examine whether in the elderly with mild cognitive impairment (MCI), the effect of physical activity measured directly following treatment, was reflected in an improvement in cognitive functioning in general or in executive functions (EF) in particular. Secondly, this study aimed to compare the effectiveness of two types of intervention, with varying intensities: walking and hand/face exercises. Forty-three frail, advanced elderly subjects (mean age: 86) with MCI were randomly divided into three groups, namely, a walking group (n=15), a group performing hand and face exercises (n=13), and a control group (n=15). All subjects received individual treatment for 30 minutes a day, three times a week, for a period of six weeks. A neuropsychological test battery, administered directly after cessation of treatment, assessed cognitive functioning. The results show that although a (nearly) significant improvement in tasks appealing to EF was observed in both the walking group and the hand/face group compared to the control group, the results should be interpreted with caution. Firm conclusions about the effectiveness of mild physical activity on EF in the oldest old can only be drawn after studies with larger number of subjects.

Recent decreasing trend in U.S. juvenile delinquency attributable to changes in maternal age.

Two documented associations, viz., a negative one between maternal age and externalizing behavior of the offspring and a positive one between externalizing behavior in childhood and the probability of later (juvenile) delinquency, lead to the prediction that cohort-changes in crime rate over the years are associated with the age of the mothers of these cohorts when the children were born. This prediction was tested by comparing U.S. crime figures between 1987 and 1997 with maternal age figures 17 years earlier (1970-1980). Both time series show a close resemblance. Although causality from two different time series cannot be asserted, the existence of such a relationship is made plausible. Two different hypotheses are presented about the possible nature of causality. Results may be of value for studies in crime epidemiology.

Interictal and postictal cognitive changes in migraine.

The question whether symptom-free migraine patients show cognitive impairments compared to matched control subjects is addressed, and also whether migraine patients show transient cognitive impairments induced by an attack. The Neuropsychological Evaluation System (NES2) was administered once in an interictal period and twice within 30 h after different migraine attacks. Since cognitive impairments could be related to attack duration or severity, cognitive performance was compared during a postictal period after sumatriptan use and during a postictal period after habitual nonvasoactive medication use. Twenty migraineurs without aura, 10 migraineurs with aura, and 30 matched headache-free controls participated in the study. During a headache-free period, migraineurs without aura responded as quickly as controls, while migraineurs with aura were slower than controls during all tasks specifically requiring selective attention. These effects were not aggravated by a preceding migraine attack, irrespective of medication use and attack duration.

Child behavior problems increased by maternal smoking during pregnancy.

We investigated the effects of maternal smoking during pregnancy on behavioral problems (i.e., not mediated by low birth weight) in 3-y-old offspring. We assessed behavioral problems in 1377 2- to 3-y-old twin pairs (registered in the Netherlands Twin Register) with the Child Behavior Checklist for ages 2-3 y (CBCL/2-3) from Achenbach, Edelbrock, and Howell. Two to 3 y earlier (i.e., soon after the birth of the twins) we collected information about the smoking habits (i.e., "never," "sometimes," and "regularly") of the mother during pregnancy. We analyzed the effect of maternal smoking on the CBCL total score and on several subscale scores for first- and second-born twins separately, and we adjusted for the possible confounding effects of birth weight, socioeconomic status, maternal age, and type of feeding (i.e., breast or bottle fed). There was a significant effect of maternal smoking on so-called "externalizing" behavioral problems (e.g., oppositional, aggressive, overactive), but not on "internalizing" behavioral problems (e.g., withdrawn, depressed, anxious), in both first- and second-born twins. The enhanced "externalizing" problems were attributed predominantly to increased aggression. Although boys have higher externalizing and aggression scores than girls, the effect of maternal smoking was the same for boys and girls.

Cognition in children does not suffer from very low lead exposure.

We studied the relationship between exposure to lead and memory and attention in children. Participants were 313 boys aged 9 to 12 years who attended special education schools in the Netherlands. Children whose possible attentional or memory problems were obviously due to causes other than lead contamination were excluded from the study. Cognition was assessed by extensive theory- based testing. Blood lead concentration was measured to assess body lead burden. Possible confounding factors that might affect blood lead level and/or cognitive functioning were assessed. Blood lead levels were higher in children with lower socioeconomic status and in children with more hand-to-mouth behavior, and varied seasonally, with higher values in spring and summer. The mean blood lead level was 44.4 microgram lead per liter blood, which is considered low. Only 2% of the children showed a slightly higher blood lead level than the American safety standard. To obtain robust measures of cognitive aspects, we performed a factor analysis. The results showed that blood lead level did not influence any of the cognitive factors. Therefore this study, despite being designed to maximize the chance of finding an effect in asymptomatic children, does not support a relationship between lead at very low doses (below 100 micrograms/liter blood) and cognition in schoolchildren.

Frequency of parental report of problem behavior in children decreases with increasing maternal age at delivery.

Child behavior problems were assessed in 1377 3-yr.-old twin pairs with the Child Behavior Check List from Achenbach (translated into Dutch language by Verhulst). The association between problem scores and maternal age at delivery of the twins was analyzed with statistical control for several potential confounding variables: birth weight of twins, maternal smoking during pregnancy, being breast or bottle fed and socioeconomic status. After controlling for all available confounding covariates, a significant linear effect for maternal age was left. Especially Externalizing behavior problems as well as the separate categories that constitute Externalizing, i.e., Aggressive, Oppositional, and Overactive, appeared to decrease continuously with increasing maternal age. This was true for both boys and girls as well as for first and secondborn twins. Evidence in support of a biological explanation of the association between maternal age and child behavior problems, is presented.

Increase in child behavior problems resulting from maternal smoking during pregnancy.

In this article, the authors investigated the effect of maternal smoking during pregnancy on behavioral problems, which were not mediated by lower birth weight, in offspring at 3 y of age. The authors used the Child Behavior Checklist for ages 2-3 y (CBCL/2-3; Achenbach, Edelbrock and Howell) to assess behavioral problems in 1,377 2- to 3-y-old healthy twin pairs. Soon after the birth of twins, the authors collected pre- and perinatal information, including smoking habits of the mother during pregnancy. The question "Did you smoke during pregnancy?" could be answered by choosing one of three possible options: (1) never, (2) sometimes, or (3) regularly. The authors analyzed the effect of maternal smoking on the Child Behavioral Checklist total score and on several subscale scores for first- and second-born twins separately, and they adjusted for the possible confounding effects of birth weight, socioeconomic status, maternal age, and having been breast- or bottle-fed. There was a significant effect of maternal smoking on so-called externalizing behavior problems (oppositional, aggressive, overactive), but not on internalizing behavior problems (withdrawn, depressed, anxious), in both first- and second-born twins. The authors primarily attributed the enhanced externalizing problems to increased aggression. Although boys had higher externalizing (and aggression) scores than girls, the effect of maternal smoking was the same for boys and girls. The authors also discuss whether maternal smoking causes externalizing behavior problems.

Cardiovascular response to physical stress in offspring of hypertensive parents: Dutch Hypertension and Offspring Study.

Blood pressure (BP) regulatory mechanisms were studied in youngsters with contrasting risks for hypertension, based on parental history, during physical stress. As a static exercise, an isometric handgrip task (22% of maximal force during 5 min) was used and a dynamic exercise task was performed on a bicycle ergometer. At rest and during stress, BP and heart rate were recorded. In order to study the adaptation of the cardiovascular system to physical stress, cardiac output and total peripheral resistance were measured in addition to indices of vagal and sympathetic influences on the heart. Heart rate and cardiac output declined significantly more in offspring of hypertensive parents during static exercise (difference in heart rate: -2.5 +/- 1.2 bpm, P = 0.04; difference in cardiac output: -9.0 +/- 4.6%, P = 0.05). This is most likely the result of a larger increase in the total peripheral resistance in youngsters at risk (difference: 13.2 +/- 6.8%, P = 0.06). No differences between the two groups were found in reactivity of BP or in the indices of sympathetic activation or vagal inhibition of the heart. The offspring of hypertensive parents showed an attenuated increase in stroke volume during the dynamic exercise task (difference at the first cycling level: -11.5 +/- 5.4%, P = 0.04), while no difference in neural activity or heart rate was found. Youngsters with a parental history of hypertension show an enhanced reactivity of total peripheral resistance during static exercise. This does not lead to a higher BP response in this group, most probably because of a larger decrease of the cardiac output. During dynamic exercise the physiological increase in stroke volume is blunted in offspring of hypertensive parents.

Left-handedness in twins: genes or environment?

Twin family data can cast light on the longstanding problem about the influences of genes and environment on the etiology of left-handedness. Therefore, hand preference was assessed in 1700 adolescent twin pairs and their parents. Left-handedness (LH) appeared not significantly enhanced among twins compared to the general population. In addition the following observations were made: (1) Significant more LH in first born twins than in second born twins. (2) Significant higher left-handedness association in MZmm pairs compared to DZmm pairs and not or may be marginally so in MZff versus DZff pairs. These results, combined with the observations that (a) left-handed fathers increase the probability of LH in sons but not in daughters; (b) LH in mothers increases LH prevalence in both sons and daughters to the same degree; and (c) very low birth weight, corrected for the effect of gestational age, increases LH prevalence in first born twins only, make an environmental explanation more likely. The possibility that exposure to prenatal male hormones - to which low birth weight and high birth stress children are more vulnerable - might be a crucial condition for the etiology of LH, is discussed.

Genetic modelling of dizygotic twinning in pedigrees of spontaneous dizygotic twins.

The inheritance of spontaneous dizygotic (DZ) twinning was investigated in 1,422 three-generation pedigrees ascertained through mothers of spontaneous DZ proband twins. DZ twinning was modelled as a trait expressed only in women. The penetrance was modelled first as a parity independent and secondly as parity dependent. The observed frequencies of maternal and paternal grandmothers with DZ twins differed significantly from the expectations under an X-linked mode of inheritance. Complex segregation analysis showed that the parity-independent phenotype of "having DZ twins" was consistent with an autosomal monogenic dominant model, with a gene frequency of 0.035 and a female-specific lifetime penetrance of 0.10. Recessive, polygenic, and sporadic models were rejected. The autosomal dominant model revealed a strong robustness against a changing population prevalence and the loss of information due to the presence of same-sexed twin pairs of unknown zygosity. When DZ twinning was modelled as a parity dependent trait, the data were compatible with an autosomal dominant model with a gene frequency of 0.306 and a penetrance of 0.03 per birth for female gene carriers.

Pupillometric assessment of compensatory effort in a memory search task under physical and pharmacologically-induced suboptimal states.

Extensive research has shown that the phasic pupil size (peak level on each trial) is a sensitive measure of the degree of mental effort demanded by a task. In the present study, the validity of the pupil response as an index of mental effort in suboptimal conditions was investigated. Thirteen males (19-29 years) performed a memory and display-search task in a practice session, followed in random order by an oxazepam session, a placebo session, a physical exercise session, and a control session. After both oxazepam and physical exercise, decision times increased, but pupil response increased only after physical exercise. This result was explained by the possibility that under physical fatigue, compensatory effort was exerted, whereas under drug-induced fatigue, subjects seemed unable to compensate for the performance decrement. The pupil response appears to be a valuable tool for gaining more insight into different effects of suboptimal states.

Cardiovascular response to mental stress in offspring of hypertensive parents: the Dutch Hypertension and Offspring Study.

OBJECTIVE: To compare blood pressure-regulating mechanisms during mental stress in two groups of offspring with contrasting risk for hypertension. DESIGN: Cardiovascular reactivity to two different types of mental stressors was studied in adolescents and young adults with two hypertensive or two normotensive parents. The two tasks used were intended to evoke either a predominantly adrenergic cardiac response (a memory search task) or a predominantly vascular response (a reaction-time task with visual search and tone avoidance). METHODS: Blood pressure and heart rate were recorded at rest and during stress. To study adaptations of the cardiovascular system to mental stress, cardiac output, total peripheral resistance and indices of vagal and sympathetic influences on the heart were measured. RESULTS: The reactivity of systolic blood pressure (SBP) to the memory search task was significantly higher in offspring of hypertensive parents, which resulted in a longer recovery after the task. In contrast, during the reaction-time task, offspring of hypertensive parents had a significantly enhanced reactivity of peripheral resistance, but no differences in heart rate or blood pressure response were observed. No differences between the two groups were found in sympathetic or vagal activity during either task measured by the ratio of pre-ejection time and left ventricular ejection time, and respiratory sinus arrhythmia, respectively. CONCLUSION: Apart from a higher reactivity of SBP during the memory search task, no other indications supporting the presence of hyperadrenergic activation of the heart in early primary hypertension were found. On the contrary, the results of the present study support the hypothesis that blood pressure responses in prehypertensive subjects are characterized by enhanced vasoconstriction rather than by increased cardiac output.

A twin-singleton comparison of problem behaviour in 2-3-year-olds.

Twin-singleton differences in problem behaviours in 2-3-year-olds were studied. Maternal ratings of children's problem behaviours were obtained with the CBCL/2-3. The twin sample consisted of 1363 twin pairs (456 MZ, 907 DZ), the sample of singletons consisted of 420 children from the general population. Results indicated that the general level of problem behaviours in twins was broadly comparable to that in singletons. Four of the seven syndromes showed lower scores for twins. These differences, however, were small and mainly caused by lower scores for DZ twins in comparison to MZ twins and singletons. Part of the difference could be attributed to the higher maternal age in the twin groups. Higher means for boys were found for the total problem score, and the Aggressive and Overactive syndromes.

Exposure to lead and specific attentional problems in schoolchildren.

A pilot study was carried out to investigate the relationship between exposure to lead and attention in children. The participants were 43 boys, 8 to 12 years of age, attending special schools for children with educational and/or learning problems (so called LOM schools). Children with probable causes of attentional or memory problems other than lead contamination were excluded from the study. Various aspects of attention were measured using neuropsychological tests. As an assessment of body lead burden, lead concentration in the boys' hair was measured by means of the Synchrotron Radiation-Induced X-ray Fluorescence technique (SXRF). Information was collected about variables that possibly could influence attention and/or body lead burden (confounding factors). A multiple regression analysis was used to determine the contribution of lead to variance in performance, after correction for confounding factors. The results showed that children with relatively high concentrations of lead in their hair reacted significantly slower in a simple reaction-time task than did children with relatively low concentrations of lead in their hair. In addition, the former were significantly less flexible in changing their focus of attention, even after correction for the influence of their delayed reaction time.

Effect of maternal smoking on birth weight of twins: a study from the Dutch Twin Register.

Since twins weigh about 20% less than singletons at birth, maternal smoking may be a more severe risk for them than for singletons. Therefore, the effect of maternal smoking during pregnancy on birth weight was investigated in a group of 5376 twins. All necessary information was collected by a questionnaire filled out by the mother of the twins. Gestational age explains more than 75% of the variance in birth weight. Other effects were tested with gestational age as a covariate. Apart from zygosity (DZ twins weigh more than MZ twins), birth order (first born twins weigh more than second born twins) and sex (boys weigh more than girls), there was a very significant birth weight reducing effect (more than 8%) maternal smoking as well as a significant influence of maternal age (young mothers give birth to smaller children). There were no interactions with maternal smoking.

Anthropometric measures, fitness and habitual physical activity in offspring of hypertensive parents. Dutch Hypertension and Offspring Study.

As part of the Dutch Hypertension and Offspring Study, subjects with contrasting risk for hypertension according to their parental history of hypertension were compared with respect to anthropometric measures and measures of fitness and physical activity. Body height, weight, two skinfolds, and blood pressure at rest were measured. Fitness was evaluated by a maximal exercise test, and habitual physical activity was assessed using a questionnaire. No differences were observed in body mass index after adjustment for slight differences in age and proportion of men between the groups (difference between groups: 0.74 kg/m2, 95% CI: -0.30, 1.78). Offspring of hypertensive parents, however, had significantly more central fat (difference between groups: 2.32 mm, 95% CI: 0.18, 4.46). No differences in fitness or physical activity were present between the two groups. The results of this study indicate a potential role for central fat in the etiology of primary hypertension. Fitness or habitual physical activity are, however, not different between groups of subjects at different risk for future hypertension.