A multi-centre prospective case-control study of campylobacter infection in persons aged 5 years and older in Australia

There are an estimated 277,000 cases of campylobacteriosis in Australia each year, most of which are thought to be sporadically acquired. To explore causes for these infections, we conducted a multi-centre case-control study of patients and community controls across five Australian States during 2001-2002. A total of 881 campylobacter cases and 833 controls aged 5 years were recruited into the study. Crude logistic analyses were conducted within various food and non-food exposure groups. A final most parsimonious multivariable logistic regression model was developed and adjusted odds ratios (aOR), 95% confidence intervals (95% CI) were derived together with adjusted population attributable risks (PAR). Consumption of undercooked chicken (aOR 4.7, 95% CI 2.6-8.4) and offal (aOR 2.0, 95% CI 1.0-4.0), ownership of domestic chickens aged<6 months (aOR 12.4, 95% CI 2.6-59.3) and domestic dogs aged<6 months (aOR 2.1, 95% CI 1.1-4.2) were found to be independent risk factors for illness in the final model. The PAR proportions indicate that eating chicken meat, either cooked or undercooked may account for approximately 30% of campylobacter cases that occur each year in Australia. These results justify the continued need for education of consumers and foodhandlers about the risks associated with the handling of raw chicken and the potential for cross-contamination.

Frequency of infectious gastrointestinal illness in Australia, 2002: regional, seasonal and demographic variation

To estimate the frequency of infectious gastroenteritis across Australia, and to identify risk factors, we conducted a national telephone survey of 6087 randomly selected respondents in 2001-2002. The case definition was three or more loose stools and/or two or more vomits in a 24-hour period in the last 4 weeks, with adjustment to exclude non-infectious causes and symptoms secondary to a respiratory infection. Frequency data were weighted to the Australian population. Multivariate logistic regression was used to assess potential risk factors including season, region, demographic and socioeconomic status. Among contacted individuals, 67% responded. The case definition applied to 7% of respondents (450/6087) which extrapolates to 17.2 million (95% CI 14.5-19.9 million) cases of gastroenteritis in Australia in one year, or 0.92 (95% CI 0.77-1.06) cases/person per year. In the multivariate model, the odds of having gastroenteritis were increased in summer and in the warmest state, in young children, females, those with higher socioeconomic status and those without health insurance.

Do larger people have more naevi? Naevus frequency versus naevus density

BACKGROUND

It is unclear which of the number or the density of naevi on the skin is the more appropriate measure of risk of melanoma. Furthermore, the relationship between the number of naevi and their density in an individual has not been explored. Thus, for example, it is unknown if larger people tend to have more naevi by virtue of having a larger skin area, or if the density of naevi is similar in people of different body sizes. In this study, we explored the relationship between the number and the density of naevi in a sample of adolescents.

SUBJECTS AND METHODS

A sample survey of naevi in 472 grade 9 secondary school students (aged 14-15 years) was conducted in Tasmania, Australia during 1992, and a subset of these individuals was followed up in 1997. Counts of naevi of various sizes were taken on the arm, leg, and back. Naevus density was estimated by using an algorithm to estimate body surface area from the height and weight of an individual. More general relationships of the naevus counts to height and weight were also explored. Finally, we considered whether the relationship between naevus density and the anthropometric variables could be confounded by exposure to ultraviolet radiation.

RESULTS

The mean number of naevi was very similar in the two samples. Naevus density was slightly lower in the 1997 sample, mainly because of increasing body size in the cohort. The numbers of naevi were only weakly related to height and weight in males, and there was essentially no relationship in females. Regression analysis showed significant relationships of weight to the back naevus counts in males in 1992 and 1997, and to the arm naevus count in males in 1997; otherwise, none of the regression coefficients for height and weight were statistically significant. This picture did not change following adjustment for potentially confounding variables indicating time spent outdoors or in the sun. Furthermore, there was no evidence that time spent in the sun was related to the body mass index.

CONCLUSIONS

It appears that the number and density of naevi in an individual are unrelated. Accordingly, with the present state of knowledge concerning the risk of melanoma, both the number and density of naevi should be considered as equally valid in future studies as markers of the risk of melanoma, and in studies on the natural history of naevi. If the disease mechanism is systemic, and not related to particular naevi, naevus density might form the better marker of risk. However, if the disease mechanism is related to effects on particular naevi, then the risk would vary in proportion to the number of naevi.

Melanin density and melanin type predict melanocytic naevi in 19-20 year olds of northern European ancestry

Recent advances in estimating the density of cutaneous melanin by spectrophotometry and the concentration of the two types of melanin (eumelanin and phaeomelanin) in hair offer the potential to define the risk of skin cancer in individuals more accurately. The presence of common melanocytic naevi on the arm is associated with an increased risk of melanoma, and in this study the associations of arm naevi with melanin density at the upper inner arm and with melanin type in hair samples were examined in a representative sample (n = 267) of 19-20 year olds of northern European ancestry. Particularly in men, the association with naevus count was stronger for cutaneous melanin density than for follicular melanin type. Adjusted for recreational sun exposure, the rank correlation coefficients were r = -0.25, 0.12 and 0.01 for men, and r = -0.17, -0.12 and 0.14 for women, for cutaneous melanin, hair eumelanin and hair phaeomelanin, respectively. The associations with less objective markers of phenotype (hair colour, eye colour, nurse-assessed skin colour, and self-reported skin reaction to unaccustomed sun) were weaker. These findings provide important new information that human susceptibility to mutations of melanocytes can be estimated by objective biological measures. The next step is to determine whether these measures also predict the risk of melanoma.

The use of spectrophotometry to estimate melanin density in Caucasians

The density of cutaneous melanin may be the property of the skin that protects it from damage by solar radiation, but there is not an accepted, noninvasive method of measuring it. To determine whether the density of cutaneous melanin can be estimated from reflectance of visible light by the skin, reflectance of 15-nm wavebands of light by the skin of the inner upper arm of each of 82 volunteers was measured at 20-nm intervals with a Minolta 508 spectrophotometer. A 3-mm skin biopsy was then taken from the same site, and four nonserial sections of it were stained with Masson Fontana for melanin. The melanin content of the basal area was calculated using the NIH Image analysis system. We show that cutaneous melanin in Caucasians can be estimated by the difference between two measurements of reflectance of visible light by the skin: those at wavelengths 400 and 420 nm. This new spectrophotometric measurement was more highly correlated (r = 0.68) with the histological measurements of cutaneous melanin than was skin reflectance of light of wavelength 680 nm (r = 0.33). Reflectances in the range of 650-700 nm have been used previously in skin cancer research. This relatively accurate measurement of melanin is quick and noninvasive and can be readily used in the field. It should provide improved discrimination of individual susceptibility to epidermal tumors in Caucasians and information about melanin's biological role in the causation of skin cancer.

Changes in self-reported skin type associated with experience of sunburning in 14-15 year old children of northern European descent

Melanoma risk differs by sun-sensitive phenotype, of which self-reported skin type (tendency to burn, inability to tan) is an indicator. If self-reports of skin type are influenced by the amount of sun exposure subjects have had, the two principal determinants of risk are linked, and stratifying by skin type would bias the estimated effect of sun exposure. Our objective was to determine whether teenagers changed their self-reports of skin type after being sunburnt. A random sample (n = 364) of 14-15 year old schoolchildren of northern European ancestry self-assessed and self-reported their skin type before and after their summer holidays. Their responses had high correlation coefficients (girls 0.71, boys 0.54) for repeatability at 4 months, but subjects who sunburnt less (more) frequently than usual that summer revised their skin type assessment to be less (more) sun-sensitive afterwards. We conclude that these 14-15 year olds were influenced by a recent experience of sunburn when reporting their skin type. A more objective measure of phenotype is needed.

Stable lead isotope profiles in smelter and general urban communities: a comparison of environmental and blood measures

High-precision lead isotope ratios and lead concentrations have been compared statistically and graphically in women of child-bearing age (n = 77) from two smelter communities and one general urban community to evaluate the relative contributions to blood lead of tissue lead stores and lead from the contemporaneous environment (soil, floor dust, indoor airborne dust, water, food). Blood lead (PbB) contents were generally low (e.g. <10 μg dL(-1)). Statistically significant isotopic differences in blood and environmental samples were observed between the three cities although isotopic differences in blood for individual subjects living in close proximity (∼200 m radius) was as large as the differences within a city. No single environmental measure dominated the biological isotope profile and in many cases the low levels of blood lead meant that their isotopic profiles could be easily perturbed by relatively small changes of environmental exposure. Apportioning of sources using lead isotopes is possibly not feasible, nor cost effective, when blood lead levels are <5 μg dL(-1). Interpretations based on statistical analyses of city-wide data do not give the same conclusions as when the houses are considered individually. Aggregating data from multiple subjects in a study such as this obscures potentially useful information. Most of the measures employed in this study, and many other similar studies, are markers of only short-to-medium integration of lead exposure. Serial sampling of blood and longer sampling times, especially for household variables, should provide more meaningful information.

Assessment of habitual sun exposure in adolescents via questionnaire--a comparison with objective measurement using polysulphone badges

The reliability and validity of sun exposure questions were examined in a group of 125 schoolchildren aged 14-15 years of northern European ancestry. We compared estimates of erythemally effective dose (EED) obtained from polysulphone badges worn on four consecutive weekend days in late spring to answers to several questions on habitual sun exposure. The polysulphone badge estimates accurately reflected the reported sun exposure of children and were highly correlated with responses to questions on habitual sun exposure obtained 12 months earlier. For the question "During weekends and school holidays, how much time do you usually spend in the sun each day", the Pearson correlation coefficients for the association with EED were 0.36 (girls) and 0.23 (boys). Adjusted for within-person variation in the EED measurements, the correlation coefficients were 0.65 (girls) and 0.43 (boys). For the question "Weekends and school holidays, where do you spend your time", the correlation coefficients were 0.18 (girls) and 0.32 (boys); the adjusted coefficients were 0.30 (girls) and 0.53 (boys). The findings suggest that "habitual' sun exposure in teenage children is a temporally stable behaviour that is reported with an acceptable degree of reliability and validity.

Sunburn associated with increased number of nevi in darker as well as lighter skinned adolescents of northern European descent

The associations of sun exposure, sunburn, skin color, and other constitutional characteristics with the density of nevi (2 mm or more in diameter) were assessed in a study of 410 secondary school children ages 14-15 years in Tasmania, Australia. Skin color was estimated by using a chromameter that measures across the visible light spectrum (400-700 nm). Skin color and lifetime history of sunburn were significant predictors of nevus density on the arms and legs of girls and boys and on the shoulders and backs of boys. The nevus density ratios between the highest and lowest exposure groups were 2.85 for the arms and legs of boys (P < 0.01), 2.19 for the arms and legs of girls (P < 0.01), and 1.72 (P = 0.03) for the shoulders and backs of boys. The increase in nevus density appeared to occur at lower levels of lifetime sunburn in children with light or medium skin than it did in children with darker skin. Darker-skinned children with a history of many sunburns ( > or = 11 lifetime sunburns) had a similar number of nevi compared with their lighter-skinned peers.