Caffeine withdrawal,sleepiness, and driving performance: What does the research really tell us?

Abstract

As a psychostimulant, caffeine is thought to reduce road accidents by keeping drivers alert and wakeful. Studies have found that caffeine can improve performance on vigilance tasks and in driving simulators under normal sleeping conditions and after sleep restriction or deprivation. However, there is increasing evidence that these beneficial effects of caffeine are due to withdrawal reversal. Studies comparing the effects of caffeine versus placebo on driving performance have tested habitual caffeine consumers deprived of caffeine from the evening before the test day. The conclusion from this review is, therefore, that improvements in driving performance and alertness after caffeine are likely to represent withdrawal reversal rather than a net beneficial effect of caffeine. Further research using designs that control for caffeine withdrawal are necessary and, accordingly, advice given to the public on use of caffeine as an antidote to tiredness and impaired performance should be reviewed.     

Caffeine withdrawal, sleepiness, and driving performance: what does the research really tell us?

As a psychostimulant, caffeine is thought to reduce road accidents by keeping drivers alert and wakeful. Studies have found that caffeine can improve performance on vigilance tasks and in driving simulators under normal sleeping conditions and after sleep restriction or deprivation. However, there is increasing evidence that these beneficial effects of caffeine are due to withdrawal reversal. Studies comparing the effects of caffeine versus placebo on driving performance have tested habitual caffeine consumers deprived of caffeine from the evening before the test day. The conclusion from this review is, therefore, that improvements in driving performance and alertness after caffeine are likely to represent withdrawal reversal rather than a net beneficial effect of caffeine. Further research using designs that control for caffeine withdrawal are necessary and, accordingly, advice given to the public on use of caffeine as an antidote to tiredness and impaired performance should be reviewed.     

What does respirator certification tell us about filtration of ultrafine particles?

Recent interest in exposures to ultrafine particles (less than 100 nm) in both environmental and occupational settings led the authors to question whether the protocols used to certify respirator filters provide adequate attention to ultrafine aerosols. The authors reviewed the particle size distribution of challenge aerosols and evaluated the aerosol measurement method currently employed in the National Institute for Occupational Safety and Health (NIOSH) particulate respirator certification protocol for its ability to measure the contribution of ultrafine particles to filter penetration. Also considered were the differences between mechanical and electrically charged (electret) filters in light of the most penetrating particle size. It was found that the sodium chloride (NaCl) and dioctylphthalate (DOP) aerosols currently used in respirator certification tests contain a significant fraction of particles in the ultrafine region. However, the photometric method deployed in the certification test is not capable of adequately measuring light scatter of particles below approximately 100 nm in diameter. Specifically, 68% (by count) and 8% (by mass) of the challenge NaCl aerosol particles and 10% (by count) and 0.3% (by mass) of the DOP particles below 100 nm do not significantly contribute to the filter penetration measurement. In addition, the most penetrating particle size for electret filters likely occurs at 100 nm or less under test conditions similar to those used in filter certification. The authors conclude, therefore, that the existing NIOSH certification protocol may not represent a worst-case assessment for electret filters because it has limited ability to determine the contribution of ultrafine aerosols, which include the most penetrating particle size for electret filters. Possible strategies to assess ultrafine particle penetration in the certification protocol are discussed.     

What is outcomes research and what can it tell us?

In 1989, Congress enacted P.L. 101-239, establishing the Agency for Health Care Policy and Research (AHCPR). Since then, practically every specialty society has developed practice guidelines for its practitioners, and every health care organization has embarked on some outcomes research. Outcomes research has become a fashion, meaning all things to all people, and runs the risk of becoming meaningless. This article attempts to reduce the confusion by clarifying what outcomes research is not delineating its several levels, along with the methods, tools, and examples appropriate to each level. The contributions of outcomes research to health care delivery innovation to date have been modest. Ultimately, we need community health information systems, which have not only the structural and process variables but also include the outcome results, to guide decision making with regard to the health of entire communities and the appropriate investment of resources to improve health.     

What do stochastic frontier cost functions tell us about inefficiency?

Recent studies using the stochastic frontier approach have suggested high levels of inefficiency in nursing home and hospital facilities. This paper makes two observations. First, one could falsely estimate high levels of inefficiency if a statistical assumption--zero skewness of the random component of the cost residual--is violated. Second, an inefficient industry may be difficult to distinguish either statistically or visually from an industry free of inefficiency. If available, panel data yields more robust estimates of cost differences among nursing homes or hospitals.     

Measuring work disability: what can administrative data tell us about patient outcomes?

OBJECTIVE: The purpose of this study was to assess the association between administrative measures of work disability and self-reported work, pain, and functional status. METHODS: We conducted baseline and follow-up interviews to assess pain, functional status, work status, and demographic factors in workers with low back injuries, carpal tunnel syndrome, and upper and lower extremity fractures. Administrative measures of work disability were obtained from the Washington State Department of Labor and Industries. RESULTS: Pain intensity and impairment levels were lowest in those who had not received any disability payments, somewhat higher for those who were no longer receiving time loss benefits, and highest for workers receiving time loss payments at the time of interview. CONCLUSIONS: Administrative measures of work disability are significantly associated with self-reported outcomes and can be an efficient tool for tracking and evaluating outcomes of medical treatments, surgical procedures, and occupational health programs.     

What can intervention studies tell us about the relationship between fruit and vegetable consumption and weight management?

Given the recent surge in obesity, effective dietary strategies for weight management are required. Because fruits and vegetables are high in water and fiber, incorporating them in the diet can reduce energy density, promote satiety, and decrease energy intake. Although few interventions have specifically addressed fruit and vegetable consumption, evidence suggests that coupling advice to increase intake of these foods with advice to decrease energy intake is a particularly effective strategy for weight management. This approach may facilitate weight loss because it emphasizes positive messages rather than negative, restrictive messages.     

Combined therapy: what does acamprosate and naltrexone combination tell us?

AIMS: Relapse prevention treatment with both acamprosate and naltrexone has been shown to be efficacious in the treatment of alcoholism. Whereas both compounds act pharmacologically differently, there is up to now only limited evidence as to whether combined treatment is efficacious and pharmacologically safe. It remains to be answered whether data justify the combination of both drugs in clinical practice. METHODS: Review of the three pre-clinical and four clinical studies that have been published to date on either combined tolerability or efficacy. RESULTS: Data available up to now show no occurrence of severe adverse events during combined treatment. Diarrhoea and nausea were shown to be the most significant side-effects. Whereas pre-clinical studies regarding efficacy of combined treatment are not yet conclusive, clinical data show the superiority of combined treatment compared with both placebo and acamprosate monotherapy. The synergistic effect of combined treatment remained after 12 weeks of drug-free follow-up. CONCLUSIONS: The combination of acamprosate with naltrexone in a clinical sample seems to be efficacious and safe. Numerous alcohol dependent patients could benefit, particularly those that responded insufficiently on monotherapeutic treatment with either acamprosate or naltrexone.     

Modelling varicella vaccination – What does a lack of surge in herpes zoster incidence tell us about exogenous boosting?

BackgroundFor decades, assessments of the impact of universal varicella vaccination on the epidemiology of varicella and herpes zoster (HZ) have been made using mathematical modelling. Decreased virus circulation and the resulting diminished exogenous boosting have been predicted to lead to a surge in HZ incidence. Lately, the exogenous boosting hypothesis has been challenged due to a lack of an extensive surge in HZ incidence in countries with, by now long-standing universal varicella vaccination.MethodsIn a deterministic compartmental transmission model of varicella zoster virus disease, we model various levels and duration of protection from boosting to explore the impact of successful childhood varicella vaccination on HZ incidence.ResultsConsidering total HZ incidence, lifelong and strong protection from boosting give a stable incidence of HZ for about 60 years followed by a decline, whereas lifelong intermediate protection leads to a decline. So does weak protection of intermediate duration. Full and short protection, lead to a small surge, while full and intermediate protection lead to the largest HZ surge. HZ incidence by age group show that total incidence is the result of opposing increasing and decreasing trends in the various age groups over time.ConclusionsThe absence of an extensive surge in HZ incidence after varicella vaccination can, especially during the first 20–30 years, occur in either strong, intermediate or weak boosting scenarios. The impact seems to depend on an interplay of the protective level and duration of the protection in determining the basic reactivation rate and the proportion of the population that is susceptible at the start of vaccination. However, the picture depends on whether the entire population or specific age groups are observed.     

Twins in metabolic and diabetes research: what do they tell us?

PURPOSE OF REVIEW: The purpose of this review is to provide a critical update of the impact of the 'thrifty phenotype hypothesis' on metabolism, and its implications for heritability estimates as obtained in so-called classical twin studies. RECENT FINDINGS: Our recent studies demonstrated a complex age or time-dependent relationship between different and independent markers of an adverse intrauterine environment, including birth weight, twin and zygosity status on one side, and distinct defects of insulin secretion and glucose metabolism on the other side. SUMMARY: These novel findings may, to some unknown extent, influence and perhaps bias the heritability estimates of type 2 diabetes-related traits obtained using classical twin analyses. The studies add to the increasing evidence of the intrauterine environment as a - or the - key player in the cause and pathophysiology of type 2 diabetes and the metabolic syndrome. We and others have shown that monozygotic twins represent a powerful tool to demonstrate nongenetic associations between low birth weight and different phenotypes of the metabolic syndrome, including type 2 diabetes, insulin resistance and, recently, hypertension. Future studies of discordant monozygotic twins may provide novel and crucial mechanistic explanations of the link between low birth weight and the metabolic syndrome.     

Dried fruit and public health – what does the evidence tell us?

A scientific workshop held in the UK explored the potential contribution of traditional dried fruits to public health, identified gaps in the evidence and addressed priorities for research. Presentations considered the categorisation and composition of dried fruits; dried fruit and gastrointestinal health; the polyphenol content of dried fruits and their potential contribution to health; dried fruit and appetite in relation to the psychology of snacking and obesity; dried fruit and dental health including its role as a snack; and conflicts in public health advice for dried fruits. A round table discussion explored the contribution of dried fruit to “five a day” fruit and vegetable intake and fibre intake, whether dried fruits have equivalence with fresh in terms of dietary advice, advice on snacking in relation to dental health and appetite control, informing the public about different types of dried fruits and avoiding consumer confusion, and future research requirements.