South African platinum mine employees reduce smoking in 5 years.

BACKGROUND: South Africa adopted comprehensive tobacco control policies in the 1990s. Smoking has since declined in the general population, but there is little information on the effect of the campaign in labour-intensive industries, especially the mining industry where workers are exposed to dust, which may interact with tobacco smoke to cause respiratory disease. OBJECTIVES: To determine the prevalence of, and trends in, smoking in employees of a South African platinum mining company, from 1998 to 2002, and to describe some demographic factors associated with their smoking habits. METHODS: This study used smoking data collected during annual fitness-to-work medical examinations. Employees were categorised into never, ever, continuous, new and ex-smokers. Data were analysed by race and age group. Age-standardised smoking prevalence rates were compared with rates in the South African general population. RESULTS: There were 80,713 records of 25,274 mine employees for the 5-year period. The decrease in smoking prevalence over this period was significant in both black and white men, but was greater in the former (from 42.9% to 29.8%, and from 47.2% to 44.7%, respectively). In 2002, the prevalence of smoking in black mine employees was 12.1% lower than that in black men in the general population. The prevalence of smoking decreased in black mine employees in all age groups (p<0.001); no such trend was seen for white mine employees. The proportion of light smokers increased significantly from 59.9% to 64.7%, with a corresponding significant decrease in the proportion of moderate and heavy smokers from 28.0% to 25.4%, and from 12.1% to 9.8%, respectively. CONCLUSION: This study showed a significant decrease in smoking prevalence over a relatively short period, despite the fact that there was no smoking cessation programme in the company. The decline can be largely attributed to the South African government's antismoking initiative and supports the drive to continue to increase excise taxes on cigarette products. Nevertheless, the relatively high prevalence of smoking in some groups of mine employees highlights the need for workplaces to support the government's initiatives to curb smoking by establishing smoking cessation and prevention programmes.

Ethics in occupational health research in South Africa

Occupational health research encompasses the same ethical issues that apply to all research on human subjects; together with unique challenges related to the workplace setting. This article covers the main principles of research ethics relating to the occupational environment; illustrated by the authors' experiences related to ethical challenges in conducting occupational research; and reports an analysis of submissions made to the Research Ethics Committee of the University of the Witwatersrand during the period 2004 to 2006 and some lessons learnt in that regard. It also provides an overview of the international and national ethical guidelines pertinent to occupational health research with a view to assisting researchers in doing ethically acceptable research

Occupational respiratory disease in mining.

This review is based on research-based literature on occupational lung disease in the mining and related industries, focusing on conditions of public health importance arising from asbestos, coal and silica exposure. Both 'traditional' and 'new' concerns about occupational respiratory disease in miners are addressed, with the inclusion of practical evidence-based findings relevant to practitioners working in developed and developing countries. Mining is not a homogeneous industry since current miners work in formal and informal operations with numerous, and often multiple, air-borne exposures. A further occupational health challenge facing primary care practitioners are ex-miners presenting with disease only after long latency. The sequelae of silica exposure remain an occupational health priority, particularly for practitioners who serve populations with concomitant HIV and tuberculosis infection and even when exposure is apparently below the statutory occupational exposure level. Coal workers' pneumoconiosis, asbestos related diseases, lung cancer and other occupational respiratory diseases remain of considerable importance even after mining operations cease. While mining exposures contribute significantly to lung disease, smoking is a major factor in the development of lung cancer and chronic obstructive airways disease necessitating a comprehensive approach for prevention and control of mining-related occupational lung disease.

Viral hepatitis in South African healthcare workers at increased risk of occupational exposure to blood-borne viruses.

The prevalence of hepatitis A, B and C antibodies was measured in a group of healthcare workers (HCWs) at increased risk of occupational acquisition of blood-borne viruses (N=402) from a large, urban referral hospital in South Africa. The aims of this study were to determine the immunity of HCWs to these agents and to recommend policy for the protection of HCWs against occupational exposure to viral hepatitis in this country. Race, sex and age were shown to be important factors influencing the presence of hepatitis A (HAV) antibodies. Most black HCWs (96.2%) are protected from HAV infection. Females have significantly higher HAV antibodies compared with males and antibodies increase with increasing age. Hepatitis B antibodies (anti-HBs) were found in 30.6% of HCWs. Anti-HBs levels were significantly associated with a past history of HBV vaccination. However, only a small proportion of HCWs (21.2%) could remember ever being immunized against HBV. For those individuals that did receive HBV vaccination (N=83), the mean number of years since their last vaccine was 6.2 years (SD +/- 3.5). HCV antibodies were found in 1.8% of HCWs at increased risk of occupational exposure. It was not possible to define whether these infections were occupationally acquired but genotyping of the HCV (in two of seven cases) showed genotype 5, the predominant South African genotype. New recommendations for the prevention of viral hepatitis in HCWs in South Africa are made, including pre-employment screening for HAV based on self-selection criteria, universal anti-HBs screening with HBV booster vaccination. HCV recommendations are based on appropriate education of HCWs about this infection and its prevention and a standardized post-exposure testing protocol.

Influence of baseline hematocrit and hemodilution on BOLD fMRI activation.

Current understanding of blood oxygenation level dependent (BOLD) fMRI physiology predicts a close relationship between BOLD signal and blood hematocrit level. However, neither this relationship nor its effect on BOLD percent activation (BPA) has been empirically examined in man. To that end, BPA in primary visual cortex in response to photic stimulation was determined in a group of 24 normal subjects. A positive linear relationship between BPA and hematocrit was seen, particularly in men. To evaluate the effect of change in hematocrit on BPA, 9 men were studied before and following isotonic saline hemodilution, resulting in an average 6% reduction in hematocrit and an 8-31% reduction in BPA. No significant change in the number of activated pixels was seen. A model of predicted BPA as a function of hematocrit and vessel size was developed, and results from this model closely mirrored the empiric data. These results suggest that hematocrit significantly influences the magnitude of BPA and that such baseline factors should be accounted for when comparing BOLD data across groups of subjects, particularly in the many instances in which hematocrit may vary systematically. Such instances include several disease states as well as studies involving sex differences, drug administration, stress and other factors. Finally, the robust agreement between predicted and empiric data serves to validate a semiquantitative approach to the analysis of BOLD fMRI data.

Reduction in BOLD fMRI response to primary visual stimulation following alcohol ingestion.

The physiology of alcohol's effects on brain function is poorly understood. Emission tomographic imaging has revealed both acute and chronic alterations in resting cerebral hemodynamics and metabolism following alcohol ingestion. However, cerebral functional integrity under these conditions has received less attention. Functional magnetic resonance imaging (fMRI) offers a non-invasive method for assessing brain functional activation. In order to assess its utility for studying the effect of alcohol on brain function, we performed fMRI with photic stimulation before and after administration of either 0.7 mg/kg alcohol (N = 12) or placebo (N = 5), resulting in peak breath alcohol levels averaging 0.069 g/dl. We found that the amplitude of visual cortical activation in response to photic stimulation was significantly reduced by approximately 33% following alcohol administration (4.0 +/- 1.7% vs. 2.7 +/- 1.3%, P = 0.02), but not following placebo (4.2 +/- 1.5% vs. 4.1 +/- 1.4%, P = 0.7). The results also suggest that the baseline right hemispheric predominance of activation in response to photic stimulation may be reduced following alcohol, suggesting a greater effect on the right hemisphere, consistent with previous studies and alcohol's known effects on visuospatial processing. In addition, through the course of each activation session, there was a progressive reduction in response following alcohol. These data demonstrate that the cerebral effects of alcohol intoxication can be studied with fMRI, and that the effects on brain function of even moderate alcohol intoxication may be widespread, may be lateralized, and may include the visual system.

Root stimulation studies in the evaluation of patients with motor neuron disease.

Nerve root stimulation may be employed in patients with motor neuron disease (MND) to rule out motor neuropathy with conduction block. The diagnostic utility of these studies is unknown, in part because the range of amplitude changes across nerve root segments in patients with active neuronal degeneration has not been well studied. We reviewed root stimulation studies in 32 patients (59 nerves) with MND and found segmental amplitude reduction from 0 to 45%, a range similar to values reported for normal subjects; there was no suggestion of conduction block based on our usual criteria.

T1 effects in sequential dynamic susceptibility contrast experiments.

Residual effects of an initial bolus of gadolinium contrast agent have been previously demonstrated in sequential dynamic susceptibility contrast MR experiments. While these residual effects quickly reach a saturation steady state, their etiology is uncertain, and they can lead to spurious estimates of hemodynamic parameters in activation experiments. The possible influence of T1 effects is now investigated with experiments in which T1 weighting is varied as well as with serial regional T1 measurements. Little evidence for significant residual T1 effects is found, suggesting instead that susceptibility effects underlie these observations. An initial saturation dose of contrast agent minimizes this effect.

The effect of dosage cards on compliance with directly observed tuberculosis therapy in hospital.

We evaluated the effect of a dosage card signed by both patient and health worker on compliance in a tuberculosis ward. Compliance was assessed by testing a urine specimen from each patient for the presence of isoniazid and rifampicin pre-intervention and at two weeks, six weeks and 16 months post-intervention. Pre-intervention compliance was 62% and increased to 88%, 91% and 93% in the short, medium and long-term, respectively (P = 0.03, P = 0.02, P < 0.01). The assumption that directly observed therapy is successfully practised in hospital is not always correct. Simple inexpensive measures can improve compliance and have an impact on tuberculosis control.

Sex differences in blood-oxygenation-level-dependent functional MRI with primary visual stimulation.

OBJECTIVE: The authors evaluated the effect of sex on data derived from activation studies using blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (MRI). METHOD: Gradient echo-echo planar imaging was used to measure BOLD signal response in the primary visual cortex in response to binocular photic stimulation in 16 healthy, young subjects (eight women and eight men). RESULTS: BOLD signal response was 38% lower in women than in men, and much of the difference was lateralized to the right hemisphere. CONCLUSIONS: Lower BOLD signal response in women may reflect a sex difference in the brain's response to a primary visual stimulation or in the physiology underlying BOLD functional MRI signal changes.

Cocaine-induced cerebral vasoconstriction detected in humans with magnetic resonance angiography.

CONTEXT: Clinical observations and case reports suggest that there are important cerebrovascular complications of cocaine use, but no studies have documented a direct link. OBJECTIVE: To determine whether low-dose cocaine administration induces cerebral vasoconstriction in healthy cocaine users. DESIGN: Randomized controlled trial. SUBJECTS: Twenty-four healthy and neurologically normal men (mean age, 29 years) reporting median cocaine use of 8 lifetime exposures (range, 3 to >40). INTERVENTION: Double-blind intravenous administration of cocaine (0.4 or 0.2 mg/kg) or placebo, with cerebral magnetic resonance angiography performed at baseline and 20 minutes following infusion. MAIN OUTCOME MEASURE: Cocaine-induced angiographic change indicative of vasoconstriction, as independently and concordantly rated by 2 reviewers blind to treatment condition. RESULTS: Cocaine-induced cerebral vasoconstriction in a dose-related fashion (P=.03), with angiograms indicative of vasoconstriction found in 5 of 8 and 3 of 9 subjects receiving 0.4- and 0.2-mg/kg cocaine, respectively, compared with 1 of 7 subjects administered placebo. Outcome stratification by frequency of self-reported lifetime cocaine use (3-10 times, 11-40 times, or >40 times) revealed a statistically stronger dose-related effect (P<.001), suggesting that greater lifetime cocaine use was associated with a greater likelihood of vasoconstriction. CONCLUSIONS: Cocaine administration induced dose-related cerebral vasoconstriction on magnetic resonance angiograms. These changes occurred at low cocaine doses and in the absence of other risk factors, including polydrug abuse, hypertension, or cerebrovascular disease. Outcome stratification by prior cocaine use statistically strengthened the relationship between cocaine administration and vasoconstriction, suggesting that cocaine may have a cumulative residual effect in promoting cerebrovascular dysfunction.

Treatment of occupational cramp with botulinum toxin: diffusion of toxin to adjacent noninjected muscles.

Over a 5-year period, 40 patients, 11 with musician's and 29 with writer's cramp, were treated with botulinum toxin A using a precise injection technique in which the hollow-bore electromyography (EMG) needle was positioned by both standard EMG and by muscle twitch evoked by stimulating current passed through it. Moderate to complete improvement in dystonia occurred in 28 patients (70%) after the first injection and in 34 patients (85%) after the second injection with better outcome in nonmusicians than in musicians. Of note, weakness of uninjected muscles, immediately adjacent to those injected, was found in 25/40 patients (63%). The most common patterns of toxin spread were from flexor digitorum sublimis to profundus, extensor carpi radialis to extensor digitorum communis, and extensor indicis proprius to extensor pollicis brevis. Spread to, and weakness of, adjacent uninjected muscles was a major factor contributing to suboptimal outcome in 6/39 (15%) such patients.

Age-related reduction in functional MRI response to photic stimulation.

Many functional imaging studies have demonstrated age-related alterations in cerebral blood flow during the resting state. However, few studies have addressed possible differences in functional response to cerebral activation. We assessed the response of visual cortex to photic stimulation in 9 normal elderly subjects and 17 normal younger subjects with blood oxygenation level dependent functional magnetic resonance imaging. We found that the amplitude of response in elderly subjects was significantly decreased compared to younger subjects (2.5 +/- 1.0% versus 4.0 +/- 1.6%, p = 0.01), suggesting a reduction in functional activation or an age-related alteration in the coupling of blood oxygenation to focal activation.

Dynamic susceptibility contrast magnetic resonance imaging in neuropsychiatry: present utility and future promise.

Dynamic susceptibility contrast magnetic resonance imaging (DSC MRI) provides a noninvasive means to create high resolution maps of the regional distribution of cerebral blood volume (CBV). Most DSC MRI studies conducted to date have focused on the evaluation of patients with cerebral neoplasms, ischemia or infarction, and epilepsy. However, preliminary work suggests that DSC MRI may also provide clinically important information for the evaluation of patients with neuropsychiatric disorders, especially dementia and schizophrenia. Additionally, with appropriate modification, DSC MRI may be used to reliably evaluate the effects of pharmacological challenges on cerebral hemodynamics. As pharmacotherapy is an important component in the treatment of a range of psychiatric disorders, the dynamic assessment of changes in cerebral perfusion associated with drug administration may ultimately lead to the development of "brain function tests" for a wide range of disorders.

Applications of dynamic susceptibility contrast magnetic resonance imaging in Neuropsychiatry.

Functional neuroimaging has assumed an important role in the cognitive and clinical neurosciences. Recently, substantial progress has been made toward developing functional magnetic resonance imaging techniques for the examination of cerebral hemodynamic changes that accompany brain function and toward earlier and better diagnosis of brain disease. Dynamic susceptibility contrast (DSC) MRI offers unique information about cerebral hemodynamics both at rest and in response to brain activation. We review the clinical applications of DSC MRI and present our experience with this modality in the evaluation of patients with neuropsychiatric disorders. Our experience suggests that DSC MRI may afford new insights into the diagnosis and treatment of cognitive disorders.

Ulnar neuropathy and dystonic flexion of the fourth and fifth digits: clinical correlation in musicians.

Peripheral nerve lesions are sometimes associated with focal dystonia. We diagnosed ulnar neuropathy in 28 of 73 (40%) cases of occupational cramp in musicians. Focal slowing of ulnar conduction across the elbow was identified in 15 of 19 (79%) patients using the near nerve technique and in 5 of 17 (29%) patients using surface recording. Ulnar neuropathy was present in 24 of 31 (77%) cases with flexion dystonia of the fourth and fifth digits and only 4 of the remaining 42 (10%) cases with other patterns of focal dystonia. Focal dystonia improved in 13 of 14 patients whose ulnar neuropathy improved and appeared or worsened in 2 patients following ulnar nerve injury. These data, together with our recent observation of a dystonic pattern of antagonist bursting in patients with isolated ulnar neuropathy (Muscle Nerve 1995, 18:606-611), suggest that ulnar neuropathy may initiate or sustain a specific dystonia, flexion of the fourth and fifth digits, by inducing a central disorder of motor control.