Bicycle helmet efficacy: a meta-analysis.

Bicycle helmet efficacy was quantified using a formal meta-analytic approach based on peer-reviewed studies. Only those studies with individual injury and helmet use data were included. Based on studies from several countries published in the period 1987-1998, the summary odds ratio estimate for efficacy is 0.40 (95% confidence interval 0.29, 0.55) for head injury, 0.42 (0.26, 0.67) for brain injury, 0.53 (0.39, 0.73) for facial injury and 0.27 (0.10, 0.71) for fatal injury. This indicates a statistically significant protective effect of helmets. Three studies provided neck injury results that were unfavourable to helmets with a summary estimate of 1.36 (1.00, 1.86), but this result may not be applicable to the lighter helmets currently in use. In conclusion, the evidence is clear that bicycle helmets prevent serious injury and even death. Despite this, the use of helmets is sub-optimal. Helmet use for all riders should be further encouraged to the extent that it is uniformly accepted and analogous to the use of seat belts by motor vehicle occupants.

Middle ear effusion: rate and risk factors in Australian children attending day care.

There have been no previous longitudinal studies of otitis media conducted in non-Aboriginal Australian children. This paper describes the rate and risk factors for middle ear effusion (MEE) in children attending day care in Darwin, Australia. A prospective cohort study of 252 children under 4 years was conducted in 9 day care centres over 12 fortnights between 24 March and 15 September 1997. Tympanometry was conducted fortnightly and multivariate analysis used to determine risk factors predicting MEE. The outcome of interest was the rate of type B tympanograms per child detected in either ear at fortnightly examinations. After adjusting for clustering by child, MEE was detected on average 4.4 times in 12 fortnights (37% of all examinations conducted). Risk factors associated with presence of effusion were younger age, a family history of ear infection, previous grommets (tympanostomy tubes), ethnicity and the day care centre attended. A history of wheeze appeared protective. These effects were modest (RR 0.57-1.70). Middle ear effusion is very common in children attending day care in Darwin. This has clinical importance, since MEE during early childhood may affect optimal hearing, learning and speech development. There is little scope for modification for many of the risk factors for MEE predicted by this model. Further study of the day care environment is warranted.

Cyanobacterial (blue-green algae) contamination in drinking water and perinatal outcomes.

OBJECTIVE: The aim of this ecological study was to examine the relationship between potential cyanobacterial exposure through drinking water during pregnancy and birth outcomes. METHOD: One hundred and fifty-six communities in South-Eastern Australia were involved, providing 32,700 singleton live newborn during the period 1992-94. Cyanobacterial occurrence and cell density (alert level) in drinking water sources during the first trimester, the total gestational period for premature births or limited to 36 weeks in term infants, and the last 12 weeks prior to preterm births or up to and including 36 weeks in term infants were used as estimates of exposure. RESULTS: There were statistically significant differences between the proportion of time during the first trimester with cyanobacterial occurrence and the percentage of births that were low birth weight (LBW) and very low birth rate (VLBW). Significant differences were also found among various categories of first trimester exposure based on average cell density and LBW, prematurity and congenital defects. However, the pattern of these results does not suggest a causal link to cyanobacteria. There were no clear dose-response relationships. Analyses based on exposure during the last 12 weeks and total gestation also showed no significant dose-response effects. CONCLUSION: The results of this study provide no clear evidence for an association between cyanobacterial contamination of drinking water sources and adverse pregnancy outcomes.

Respiratory effects associated with indoor nitrogen dioxide exposure in children.

BACKGROUND: The human health effects of exposure to indoor nitrogen dioxide (NO2) are unclear, and few studies have examined the effects of short-term peak levels of exposure. METHODS: The association between indoor exposure to NO2 and respiratory illness was examined in 388 children aged 6-11 years. The NO2 levels were monitored during winter in 41 classrooms, from four schools with unflued gas heating and four schools with electric heating. Each classroom was monitored daily with 6-hour passive diffusion badge monitors over nine alternate weeks, and with hourly monitors over two of those weeks. Children living in homes with unflued gas appliances were also monitored daily over four evenings during times of gas use. RESULTS: Exposure to NO2 at hourly peak levels of the order of > or = 80 ppb, compared with background levels of 20 ppb, was associated with a significant increase in sore throat, colds and absences from school. An increase in cough with phlegm was marginally significant. Significant dose-response relationships were demonstrated for these four measures with increasing levels of NO2 exposure. CONCLUSIONS: Short-term peak levels of exposure are important to consider in relation to adverse respiratory effects associated with NO2 exposure.

Characteristics of longer consultations in Australian general practice.

OBJECTIVE: To assess the association between general practitioner (GP) billing for "longer" consultations, patient factors linked with health care need, and other consultation characteristics. DESIGN: Retrospective analysis of data from Medicare (1984-1992), Australian Morbidity and Treatment Survey (1990-1991) and Australian Capital Territory Record Linkage Study (1988-1992). SETTING: Australian general practice, 1984 (introduction of Medicare) to 1992. MAIN OUTCOME MEASURES: Consultations billed as longer (> or = 20 or > 25 minutes) compared with standard; type of billing (bulk or private); patient health care need (defined as health and sociodemographic factors linked to worse health outcomes); consultation continuity, type of care given and number of problems managed. RESULTS: Longer billed consultations increased between 1984 and 1992, from 2.8% to 6.7% of all standard and longer consultations. Longer consultations were more likely to be bulk-billed than privately billed (odds ratio [OR], 1.74). They were more likely than standard consultations to deal with psychological diagnoses (OR, 2.06; 95% confidence interval [95% Cl], 1.83-2.32) or multiple problems (OR for four versus one diagnosis, 5.18; 95% Cl, 4.31-6.22) and to involve patients aged under 50 years, new to the practice or with new problems, but not chronic disease. In the ACT, those billed for longer consultations were more commonly tertiary educated (OR, 1.99; 95% Cl, 1.35-2.94), bulk-billed (OR, 2.75; 95% Cl, 2.51-3.10), aged 40-49 years and non-obese. CONCLUSION: Longer billed consultations were not associated with greater patient need, other than psychosocial need, but with bulk billing and patient socioeconomic advantage. However, evaluation was complicated by the effects of continuity of care and number of problems managed in the consultation.

Health effects of exposure to cyanobacteria (blue-green algae) during recreational water-related activities.

The aim of this study was to investigate effects on health of exposure to cyanobacteria as a result of recreational water activities. Participants, who were aged six years and over, were interviewed at water recreation sites in South Australia, New South Wales and Victoria on selected Sundays during January and February 1995. Telephone follow-up was conducted two and seven days later to record any subsequent diarrhoea, vomiting, flu-like symptoms, skin rashes, mouth ulcers, fevers and eye or ear irritations. On the Sundays of interview, water samples from the sites were collected for cyanobacterial cell counts and toxin analysis. There were 852 participants, of whom 75 did not have water contact on the day of interview and were considered unexposed. The 777 who had water contact were considered exposed. No significant differences in overall symptoms were found between the unexposed and exposed after two days. At seven days, there was a significant trend to increasing symptom occurrence with duration of exposure (P = 0.03). There was a significant trend to increasing symptom occurrence with increase in cell count (P = 0.04). Participants exposed to more than 5000 cells per mL for more than one hour had a significantly higher symptom occurrence rate than the unexposed. Symptoms were not correlated with the presence of hepatotoxins. These results suggest symptom occurrence was associated with duration of contact with water containing cyanobacteria, and with cyanobacterial cell density. The findings suggest that the current safety threshold for exposure of 20,000 cells per mL may be too high.

Repetitive industrial work and neck and upper limb disorders in females.

A cross-sectional study was performed in which physical examinations of the neck and upper limbs were conducted on 82 currently working female industrial workers with exposure to repetitive work tasks and on 64 currently working referent subjects without exposure to repetitive work tasks. Associations between results of symptom questions and physical examination were sought with variables related to the work environment and to the individuals. In a multivariate model, there were statistically significant associations between exposure to repetitive work and diagnoses in both the neck/shoulders (prevalence odds ratio, POR = 4.6) and elbows/hands (POR = 3.5). In addition, age (POR = 1.9, 75th vs. 25th percentiles), tendencies towards subjective muscular tension (POR = 2.3), and stress/worry (POR = 1.9) were also associated with diagnoses in the neck/shoulders; however, there was not an association between these variables and the prevalence of diagnoses in elbows/hands. Standardized evaluation of videotape recordings in 74 of the industrial workers revealed significant associations between neck flexion, and elevation and abduction of the arm and the prevalence of neck/shoulder diagnoses. In the multivariate model, neck flexion was significantly associated with diagnoses in the neck/shoulders (p = 0.005). In addition, low muscle strength, lack of emotional well-being at work, and a variety of psychosomatic symptoms were associated with diagnoses in the neck/shoulders (all p < 0.001). Lack of strength was also associated with disorders of elbows/hands (p = 0.007). This study demonstrated a substantial prevalence of neck and upper limb disorders associated with repetitive work performed with a flexed neck and elevated and abducted arms, as well as a possible potentiation of these ergonomic factors by certain personal traits in some workers.

An assessment of neck and upper extremity disorders by questionnaire and clinical examination.

To study the usefulness of a screening questionnaire for neck/upper extremity complaints, 165 women in either repetitive industrial, or mobile and varied work, were studied by the questionnaire and by a detailed clinical physical examination. A total of 94 subjects recorded complaints in the questionnaire. In 140 subjects findings were recorded at the examination. Most subjects with findings at the clinical examination of shoulders reported complaints in the questionnaire (sensitivity 80%). For the other anatomical regions, the sensitivity was rather low (42-65%). For all regions, most subjects without findings reported no complaints (specificity 77-97%). A total of 75 subjects were given clinical diagnoses according to a set of predetermined diagnostic criteria. The capacity of the questionnaire to identify diagnoses of shoulders was higher (sensitivity 92%) than for the other regions (66-79%). Of subjects who did not qualify for diagnosis, a majority (specificity 71-81%) did not report complaints in the questionnaire. We conclude that the questionnaire approach gives a fairly good picture of the neck/upper extremity status of a working female population. However, a clear view of the size of a problem is obtained only by a detailed clinical examination, particularly as regards the neck, elbows and hands, for which the questionnaire gave an underestimate.

Focal epilepsy and exposure to organic solvents: a case-referent study.

Organic solvent exposure was studied in 104 cases of idiopathic focal epilepsy and 312 matched referents. Exposure to solvents was classified as O, I, II, or III on the basis of occupational codes. The relative risk (RR) of epilepsy for those in exposure class I, II, or III, relative to O, was estimated using conditional logistic regression. An increasing trend in RR was observed with higher exposure classes. The attributable risk for cases with focal epilepsy of deep hemispherical origin was estimated to be 8%.

Ferruginous bodies and pulmonary fibrosis in dead low to moderately exposed asbestos cement workers: histological examination.

Histological slides from the lungs of 89 dead asbestos cement workers have been examined with respect to ferruginous bodies and fibrosis. The results have been compared with individually matched controls with no known exposure to asbestos, and related to asbestos exposure, expressed as duration of exposure and cumulative asbestos dose, and smoking habits. The asbestos cement workers studied had been employed for on average 15 years, with a mean cumulative dose of 26 fibre-years per ml (f-y/ml). Clear dose-response relations between exposure (duration of exposure and cumulative asbestos dose) and level of ferruginous bodies were found. An association was evident already at a low cumulative dose (1-10 f-y/ml). Fibrosis was more common and more pronounced among the exposed workers than among controls. An association between ferruginous bodies and fibrosis was also found. Among the controls, but not among exposed workers, there was an association between smoking history and fibrosis.