J. Snel

Tracking of health and risk indicators of cardiovascular diseases from teenager to adult: Amsterdam growth and health study

Cardiovascular disease is recognized as a serious public health problem. Because the underlying pathological processes start shortly after birth, tracking of recognized cardiovascular disease indicators during childhood and adolescence can help in developing preventive pediatric strategies. A prospective follow-up of both genetic and behavioral lifestyle parameters (serum cholesterol, blood pressure, percentage body fat, maximal oxygen uptake (VO2max), smoking, physical inactivity, and type A behavior) was designed. In the Amsterdam Growth and Health Study a population of 93 males and 107 females was measured annually from 1977 to 1980 and a fifth measurement was made in 1985. In that way longitudinal data covering a period of 8 years was collected for a group of adolescents/adults between 13 and 21 years of age. Analyses of these parameters provided the following results: The stability over the 9 years of tracking cardiovascular disease indicators, measured as the interperiod correlations, is fairly high. It varies from 0.4 to 0.8 in percentage body fat, cholesterol, and VO2max. Blood pressure values are low (between 0.3 and 0.4). The probability of 13-year-olds having relatively high values of cardiovascular disease indicators on the basis of a quartile distribution with that at age 21 indicated a moderate to high predictive value. According to the literature, the levels of subjects that are continuously relatively high over the years are more in the direction of optimal health than risk values. The exception is for percentage body fat. Interrelation of the seven cardiovascular disease indicators in constantly relatively high-risk and relatively low-risk groups during the teenage period, measured during young adulthood (21.5 years), appeared to be weak: only males and females with a high percentage body fat and a low VO2max showed significantly high total cholesterol, low high-density lipoprotein cholesterol, and high total cholesterol/high-density lipoprotein cholesterol levels. From the three environmental cardiovascular disease indicators (smoking, physical activity, and type A/B behavior) measured in 1985, only physical activity was significantly correlated among males and females with high-density lipoprotein cholesterol, percentage body fat, and VO2max. It can be concluded that measurement of percentage body fat in the early teenage period seems to be the most important cardiovascular disease indicator in predicting risk levels in the young adult. The amount of physical activity measured at young adult age is the only behavioral parameter to show a significant interrelation with other cardiovascular disease risk indicators.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of caffeine on information processing stages in well rested and fatigued subjects

The effects of caffeine on different information processing stages were examined by using choice reaction time tasks. Independent variables were stimulus degradation, stimulus-response compatibility, time-uncertainty, state of the subject, and caffeine treatment. The task variables were assumed to affect the following processing stages; encoding, response selection and motor preparation, respectively. A 200 mg dose at the beginning of the experiment and a maintenance dose of 50 mg caffine or lactose half-way through the session were administered to well rested and fatigued subjects, double-blind and deceptively. Behavioural measurements, event-related potentials (ERPs) and mood questionnaires were used to assess caffeine effects. The data showed that caffeine shortened reaction time. This effect showed an interaction with stimulus degradation and time uncertainty. In addition, ERP results supported the view that caffeine increases cortical arousal and perceptual sensitivity. Stimulating effects of caffeine were mainly located at input and output stages of the information processing system. Central processes were unaffected by caffeine. Fatigued subjects showed larger improvements in performance after caffeine than well-rested subjects. The results also indicated that caffeine effects were not stimulating in all subjects: 6 out of 30 subjects did not show arousing effects of caffeine.

Impaired executive function in male MDMA (“ecstasy”) users

RationaleLong-term users of ecstasy have shown impaired performance on a multitude of cognitive abilities (most notably memory, attention, executive function). Research into the pattern of MDMA effects on executive functions remains fragmented, however.ObjectivesTo determine more systematically what aspects of executive function are affected by a history of MDMA use, by using a model that divides executive functions into cognitive flexibility, information updating and monitoring, and inhibition of pre-potent responses.MethodsMDMA users and controls who abstained from ecstasy and other substances for at least 2 weeks were tested with a computerized cognitive test battery to assess their abilities on tasks that measure the three submodalities of executive function, and their combined contribution on two more complex executive tasks. Because of sex-differential effects of MDMA reported in the literature, data from males and females were analyzed separately.ResultsMale MDMA users performed significantly worse on the tasks that tap on cognitive flexibility and on the combined executive function tasks; no differences were found on the other cognitive tasks. Female users showed no impairments on any of the tasks.ConclusionsThe present data suggest that a history of MDMA use selectively impairs executive function. In male users, cognitive flexibility was impaired and increased perseverative behavior was observed. The inability to adjust behavior rapidly and flexibly may have repercussions for daily life activities.

Cerebral event-related potentials associated with selective attention to color: Developmental changes from childhood to adulthood

Event-related potentials were recorded from 80 participants ranging in age from 7 to 24 years while they attended selectively to stimuli with a specified color (red or blue) in an attempt to detect the occurrence of target stimuli. Color attention effects were identified as frontal selection positivity (FSP; 140-275 ms), selection negativity (SN; 150-300 ms), and N2b (200-450 ms), whereas target detection was reflected in P3b (300-700 ms). There were age-related decreases in the latencies of FSP, N2b, and P3b that paralleled decreases in reaction time and error rates. Also, the SN amplitude increased with advancing age, whereas both N2b and P3b showed changes in scalp topography. These results represent neurophysiological evidence that the efficiency of visual selective processes increases during childhood and adolescence. Developmental growth may take place at both relatively early and late levels of visual selective information processing.

Aging, caffeine, and information processing: an event-related potential analysis

Structural and energetic processes in information processing were studied in young and elderly subjects. A visually focussed selective search task was used, in which subjects had to select relevant information, followed by controlled memory search processes to locate a target item. Caffeine was used to manipulate the energetic state of the subjects. During task performance event-related potentials (ERPs) and reaction time (RT) were recorded. Subjects were 15 young and 15 elderly healthy, non-smoking, moderate caffeine consumers (250-600 mg/day). Before the experimental sessions they abstained from caffeine for > or = 12 h. In the experiment subjects received 250 mg caffeine or placebo dissolved in decaffeinated coffee. RT data seem to indicate that aging effects are at least partly due to a shift in the speed-accuracy trade-off. ERP results provide evidence for decreased levels of energy resources in the elderly. The identification of relevant information and stimulus evaluation processes were delayed in the elderly, suggesting an additional effect of aging on structural processes. Caffeine improved performance and increased the amplitude of the N1, N2b, and P3b, in both young and old subjects. These results suggest that caffeine makes more energy resources available for task performance. The effects of aging on P3b latency were counteracted by caffeine. Other caffeine effects did not differ significantly between young and elderly subjects.

Effects of caffeine on sleep and cognition

Caffeine can be used effectively to manipulate our mental state. It is beneficial in restoring low levels of wakefulness and in counteracting degraded cognitive task performance due to sleep deprivation. However, caffeine may produce detrimental effects on subsequent sleep, resulting in daytime sleepiness. This justifies a careful consideration of risks related to sleep deprivation in combination with caffeine consumption, especially in adolescents. The efficacy of caffeine to restore detrimental effects of sleep deprivation seems to be partly due to caffeine expectancy and to placebo effects. The claim that stimulant effects of caffeine are related to withdrawal or withdrawal reversal seems to be untenable.

Caffeine effects on perceptual and motor processes.

The effects of a single dose of caffeine on specific information processing operations were examined by using a visual selective attention task in which subjects were asked to select between a left and right hand response on the basis of two different target letters. The target was presented on a predefined position in the visual field and was either presented alone or with flanker letters, calling for the correct, the incorrect or no specific response. A dose of 3 mg/kg body weight caffeine or lactose, dissolved in a cup of decaffeinated coffee, was administered double blind and deceptively to overnight abstinence coffee drinkers. Behavioural measures were supplemented by psychophysiological measures. The present results replicated the basic findings obtained in this paradigm. The results indicated that the time to localise the target decreased and response preparation started earlier after caffeine than after placebo. These caffeine effects did not interact with the time subjects spent on the task or with the reaction time distribution, which might be due to a high level of practice.

A Longitudinal study on smoking in Relationship to Fitness and Heart Rate response

PURPOSE Smoking has been shown to be associated with impaired cardiovascular fitness and reduced heart rate response to exercise. It is not known whether these associations are present in adolescence and young adults, and whether they change over time. METHODS Maximal oxygen uptake ([OV0312]O(2max)), maximum treadmill slope (Slope(max)), resting heart rate (HR(rest)), heart rate at submaximal exercise (HR(submax)), heart rate reserve (HRR), and maximum heart rate (HR(max)) were measured one to nine times between ages 13 and 36 in 298 male and 334 female participants of the Amsterdam Growth and Health Longitudinal Study. Generalized estimating equation analyses were used to study the longitudinal relationship between smoking and cardiovascular fitness and heart rate response to exercise, whereas linear regression analyses were used to study the reversibility of smoking effects at age 36. RESULTS Moderate to heavy smoking (>/=10 g of tobacco per day) was longitudinally and negatively related to [OV0312]O(2max), Slope(max), HR(submax), and HR(max). With increasing age, the negative relationship between smoking and [OV0312]O(2max), Slope(max), and HR(max) became stronger in males. Cross-sectional analyses suggested that the adverse effects of smoking were reversible in 36-yr-old males. CONCLUSION Cardiovascular fitness and heart rate response to exercise are already reduced in young healthy smokers. In men, the adverse effects of smoking become stronger with increasing age but appear to be reversible at age 36.

Caffeine improves anticipatory processes in task switching

We studied the effects of moderate amounts of caffeine on task switching and task maintenance using mixed-task (AABB) blocks, in which participants alternated predictably between two tasks, and single-task (AAAA, BBBB) blocks. Switch costs refer to longer reaction times (RT) on task switch trials (e.g. AB) compared to task-repeat trials (e.g. BB); mixing costs refer to longer RTs in task-repeat trials compared to single-task trials. In a double-blind, within-subjects experiment, two caffeine doses (3 and 5mg/kg body weight) and a placebo were administered to 18 coffee drinkers. Both caffeine doses reduced switch costs compared to placebo. Event-related brain potentials revealed a negative deflection developing within the preparatory interval, which was larger for switch than for repeat trials. Caffeine increased this switch-related difference. These results suggest that coffee consumption improves task-switching performance by enhancing anticipatory processing such as task set updating, presumably through the neurochemical effects of caffeine on the dopamine system.

The effects of caffeine on visual selective attention to color : An ERP study

Event-related potentials were recorded from 11 subjects after ingesting caffeine (250 mg) or placebo. Subjects were instructed to attend selectively to stimuli with a specified color (red or blue) in order to react to the occurrence of a target within the attended category. Reaction times revealed faster responses for the caffeine condition, whereas no differences in strategy were observed. Color attention effects were identified as frontal selection positivity, occipital selection negativity, and N2b, whereas target detection was reflected in P3b. Effects of treatment were found as a more positive-going frontal P2 component in the caffeine condition. In addition, an interaction between attention and treatment could be observed on the N2b component. This pattern of results suggests that caffeine yields a higher overall arousal level, more profound processing of both attended and unattended information, and an acceleration of motor processes.