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BMJ 2005; 330 doi: https://doi.org/10.1136/bmj.330.7505.1411 (Published 16 June 2005) Cite this as: BMJ 2005;330:1411
  1. Christopher Martyn, associate editor (cmartyn{at}bmj.com)

    Aircraft noise affects cognitive development in children

    Everyone finds unwanted noise annoying, but children may be especially vulnerable to its effects, partly because they cope with stressors less well than adults, and partly because noise might interfere with learning at a critical developmental stage. Children may react by tuning out unwanted noise and, in the process, pay less attention to other inputs, such as a teacher's speech. A new study adds to the developing literature on the negative effect of noise on learning.

    The study used over 2800 children aged 9-10 years, attending schools located near three major airports in Spain, the Netherlands, and the United Kingdom. The investigators assessed level of noise caused by aircraft and traffic around the school, and related these levels to the results of cognitive performance testing and health questionnaires. Chronic exposure to aircraft noise had deleterious effects on reading comprehension even after adjustment for socioeconomic differences between high noise and low noise schools (figure). A limitation of the study is its cross sectional design, but the results show, perhaps unsurprisingly, that schools in noisy places are less than ideal educational environments.

    Lancet 2005;365: 1942-9

    GI endoscopy is not a route for transmission of hepatitis C virus

    Surgical operations are one way in which the hepatitis C virus (HCV) is transmitted and, even though the evidence is weak, a faint cloud of suspicion hangs over less invasive procedures too. In Italy and France, for example, blood donors are turned away if they have had a recent gastrointestinal endoscopy. The results of a large prospective study from Italy now show that this procedure is blameless.

    The investigators measured the incidence of HCV seroconversion in more than 9000 patients from three centres in the six months after endoscopy and in a large comparison group of blood donors. In two of the centres, biopsy specimens were taken with reusable forceps. Although a small percentage of the endoscopy group was lost to follow-up, none of the 8260 people retested became positive for the HCV antibody after the procedure. This included 912 patients whose endoscopy had been performed with an instrument previously used on an HCV carrier. In contrast, four blood donors became positive for the HCV antibody and HCV RNA, an incidence of 0.042 cases per 1000 person years. Each of them had had minor surgery before the second test. The conclusion is that the risk of HCV transmission by endoscopy is extremely low when instruments are cleaned using the proper techniques.

    Annals of Internal Medicine 2005;142: 903-9

    Gulf war veterans' health

    The Gulf War ended more than 14 years ago but controversy continues over whether the events and conditions experienced by the combatants caused persistent ill health. Without doubt, many of the people who were deployed report debilitating symptoms. More than 500 000 US personnel took part in the military action in the Gulf War. By 2001, nearly 20% were receiving some form of disability compensation.

    The US Department of Veterans Affairs has now carried out a cross sectional survey of the prevalence of 12 conditions in 1061 deployed and 1128 non-deployed US veterans. Structured interviews were used to elicit symptoms and history of illness. Physical examination was supplemented by laboratory tests, which included pulmonary function and peripheral nerve conduction. Deployed veterans reported dyspepsia, a group of common skin conditions, fibromyalgia, and chronic fatigue syndrome more often than the non-deployed control group. The association was most striking for chronic fatigue syndrome, where the odds ratio was 40.6. But abnormalities on physical examination and most common laboratory tests occurred at the same rate in the two groups. Mean score on an overall measure of self reported health, the SF-36, was slightly lower in deployed participants, but the investigators conclude that the current physical health of deployed veterans is similar to that of non-deployed veterans.

    Annals of Internal Medicine 2005;142: 881-90

    Simple measures reduce aflatoxin exposure

    Staple foods in the developing world, particularly maize and groundnuts, are often contaminated with aflatoxins, metabolites of Aspergillus species. Apart from their well known carcinogenic action on the liver, they also impair growth and the development of the immune system in children. Levels of exposure among sub-Saharan Africans are many times higher than those allowed by regulation in Europe and the United States.

    Food contamination with aflatoxins occurs mainly during storage of harvested crops, and a randomised trial among subsistence farmers in a rural area of Guinea finds that a package of low technology interventions designed to improve conditions of storage reduces the amount of aflatoxin present in the crop, and substantially lowers aflatoxin exposure in those eating it. Farmers and their families from 20 villages took part. In 10 of the villages, farmers were shown how to identify and discard mouldy groundnuts, dry the remaining nuts on mats made from natural fibre instead of on the ground, and store them in conditions that mimimise humidity. In the other 10 villages farmers followed traditional practices. Measurement of blood aflatoxin-albumin adducts immediately after harvest showed little difference between the two groups of villages, but by five months after the harvest levels in villagers in the intervention group were half those in villagers in the control group (figure).

    Lancet 2005;365: 1950-6

    Isoniazid prevents tuberculosis in HIV infected men

    The annual incidence of tuberculosis in gold miners in South Africa now exceeds 4% largely because of a combination of occupational exposure to silica dust and a high prevalence of HIV among miners. The figure is all the more striking because control measures using directly observed short course chemotherapy based on rifampicin and annual chest x ray screening are already in place.

    The investigators used an ingenious study design, inviting employees in random sequence to attend a workplace clinic. They found that isoniazid, when self administered in a dose of 300 mg/day for six months, was moderately effective as a primary prevention measure in HIV positive workers without current evidence of active tuberculosis. Incidence, over a median follow-up of 22 months, was reduced by 38% overall and by 46% in men who had not had tuberculosis before the study. Even so, the incidence remains appallingly high and, as the authors point out, additional strategies are needed. One suggestion is to extend preventive treatment to include individuals with a history of tuberculosis. Current guidelines do not recommend secondary prevention in tuberculosis.

    JAMA 2005;293: 2719-25

    Neither vitamin E nor donepezil prevents progression to Alzheimer's disease

    Mild cognitive impairment is thought to represent a transitional state between the cognitive changes of normal ageing and the earliest clinical features of Alzheimer's disease. The rate of progression to clinically diagnosable Alzheimer's disease is 10-15% per year, in contrast to a rate of 1-2% per year among normal elderly people. As donepezil, a cholinesterase inhibitor, and vitamin E have both been shown to be of limited benefit in slowing progression of cognitive decline in patients with moderate to severe Alzheimer's disease, hopes were high that these treatments would be more effective when used at the earlier stage of mild cognitive impairment.

    Unfortunately, the results of a randomised controlled trial that compared both these treatments against placebo are deeply disappointing (figure). Nearly 800 people aged 55 to 90 from centres in the United States and Canada who fulfilled criteria for the diagnosis of amnestic mild cognitive impairment took part. During the three year study period, 214 progressed to dementia, almost entirely of the Alzheimer type. Neither treatment reduced the rate of progression to Alzheimer's disease. Although an initial benefit of donepezil was seen during the first year, it was not sustained.

    Figure3

    Credit: NEW ENGLAND JOURNAL OF MEDICINE

    New England Journal of Medicine 2005;352: 2379-88

    Initial advantage of endovascular repair of abdominal aortic aneurysms is not sustained

    Two randomised trials have shown that endovascular repair of abdominal aortic aneurysms is associated with considerably lower perioperative mortality than conventional open repair. Whether this short term advantage persists is another matter. Uncontrolled studies suggest that endovascular repair might require subsequent reintervention more often and that there is a continued risk of aneurysm rupture. Longer term data from one of the randomised trials shows that the survival advantage of endovascular repair is not sustained after the first postoperative year.

    Two years after randomisation, the cumulative survival rates were 89.6% for open repair and 89.7% for endovascular repair. The cumulative rates of aneurysm related death, however, were lower in the group treated by endovascular repair. Although this difference was accounted for by events occurring in the perioperative period, there was no significant difference in subsequent aneurysm related mortality between the groups.

    An accompanying editorial (pp 2443-5) suggests several possible explanations for the preponderance of late deaths in the endovascular group. One is simply chance, in view of the small number of events. Another is that patients who have survived the stress of open repair may be less likely to die in the first few months after surgery than patients who have undergone endovascular repair because the latter group has not been subjected to a conventional surgical procedure. That is to say, the survival advantage of the less invasive approach to aneurysm repair results from postponing death in higher risk patients for some months after the operation. A third possibility is that endovascular repair may increase late mortality by failing to prevent rupture or by causing complications. The last suggestion isn't borne out by the data so far, but longer follow-up will be needed to exclude it.

    New England Journal of Medicine 2005;352: 2398-405

    Good treatment outcomes can be achieved in homeless people with tuberculosis

    JAMA's theme issue on tuberculosis contains a nationwide survey of tuberculosis in homeless people in the United States-a high risk group that is difficult to study and difficult to treat. Homeless people don't get enumerated in censuses, so incidence is impossible to determine. Instead, the researchers calculated the proportion of all reported cases of tuberculosis that occurred in homeless people (figure). Over the past 10 years this proportion has remained stable at around 6%, although, as the map shows, there is a geographical divide with higher proportions occurring in western and some southern states. Most homeless people with tuberculosis are men aged 30-59. Compared with people with homes, homeless people with tuberculosis are more likely to be in jail, to misuse alcohol or other drugs, and to be HIV positive. They are also more likely to be infectious, but not more likely to be drug resistant.

    Many risk factors for tuberculosis overlap with risk factors for persistent homelessness, so these findings are not unexpected. As the authors point out, the information should be useful in devising strategies for interrupting the transmission of Mycobacterium tuberculosis. Encouragingly, the survey showed that, once diagnosed, homeless people with tuberculosis received good case management and had excellent treatment outcomes.

    JAMA 2005;293: 2762-6

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