TRENDS IN PARTICULATE MATTER AND MORTALITY: AN APPROACH TO THE ASSESSMENT OF UNMEASURED CONFOUNDING

We propose a method for diagnosing confounding bias under a model which links a spatially and temporally varying exposure and health outcome. We decompose the association into orthogonal components, corresponding to distinct spatial and temporal scales of variation. If the model fully controls for confounding, the exposure effect estimates should be equal at the different temporal and spatial scales. We show that the overall exposure effect estimate is a weighted average of the scale-specific exposure effect estimates. We use this approach to estimate the association between monthly averages of fine particles (PM2.5) over the preceding 12 months and monthly mortality rates in 113 U.S. counties from 2000-2002. We decompose the association between PM2.5 and mortality into two components: 1) the association between “national trends” in PM2.5 and mortality; and 2) the association between “local trends,” defined as county-specificdeviations from national trends. This second component provides evidence as to whether counties having steeper declines in PM2.5 also have steeper declines in mortality relative to their national trends. We find that the exposure effect estimates are different at these two spatio-temporalscales, which raises concerns about confounding bias. We believe that the association between trends in PM2.5 and mortality at the national scale is more likely to be confounded than is the association between trends in PM2.5 and mortality at the local scale. If the association at the national scale is set aside, there is little evidence of an association between 12-month exposure to PM2.5 and mortality.

Cellular telephone use and time trends in brain tumour mortality in Switzerland from 1969 to 2002

A rising concern exists that with the widespread use of mobile communication technologies, the incidence of brain tumours may increase. On the basis of data from the Swiss national mortality registry from 1969 to 2002, annual age-standardized brain tumour mortality rates per 100,000 person-years were calculated using the European standard population. Time trend analyses were performed by the Poisson regression for six different age groups in men and women separately. The study period was divided into two intervals: before and after 1987, when the analogue mobile technology was introduced in Switzerland. Age-standardized brain tumour mortality rates ranged between 3.7 and 6.7 for men and 2.5 and 4.4 for women per 100,000 person-years. For the whole study period, a significant increase in brain tumour mortality was observed for men and women in the older age groups (60-74 and 75+ years) but not in the younger ones in whom mobile phone use was more prevalent. Time trend analyses restricted to data from 1987 onwards revealed relatively stable brain tumour mortality rates in all age groups. For instance, the annual change in brain tumour mortality rate for the 45-59-year age group was -0.3% (95% confidence interval: -1.7; 1.1) for men and -0.4% (95% confidence interval:-2.2; 1.3) for women. We conclude that after the introduction of mobile phone technology in Switzerland, brain tumour mortality rates remained stable in all age groups. Our results suggest that mobile phone use is not a strong risk factor in the short term for mortality from brain tumours. Ecological analyses like this, however, are limited in their ability to reveal potentially small increases in risk for diseases with a long latency period.

Current trends in hormone replacement therapy: perceptions and usage

OBJECTIVE: To determine whether physicians' confidence in the use of hormone replacement therapy (HRT) for climacteric symptoms has been affected by the negative media interpretation of data from landmark studies investigating HRT usage such as the Women's Health Initiative (WHI) study. METHODS: A structured questionnaire was completed via the internet by European and US gynecologists, obstetrician/gynecologists and general practitioners - all experienced in treating women with climacteric symptoms. RESULTS: Six hundred physicians completed the survey in six countries. Overall, 98% agreed that the menopause significantly affects quality of life and 97% considered that the majority/all of their patients experienced positive benefits from HRT. Most physicians (90%) believed the benefits of HRT outweigh the risks in suitable patients, and 92% would prescribe HRT for themselves/spouse/family. For treatment of atrophic vaginitis, 86% agreed that local estrogen was the most effective course of action. While 82% of participants were aware of the latest recommendations on low-dose HRT, and estrogen dose in particular, 67% cited lowering the progestogen dose as important. With regard to the recent negative media coverage on HRT, 78% of physicians felt this was unjustified. CONCLUSIONS: These results provide reassurance that health-care professionals in Europe and the US, experienced in treating women with climacteric symptoms, have not lost confidence in HRT. Despite a consensus on the importance of lowering the dose of HRT and a focus on estrogen, there remains a need to heighten prescribers' awareness on the pivotal role that a lower progestogen dose plays in optimizing the risk-benefit profile.

Changing trends in causes and patterns of facial fractures in children

OBJECTIVE: To review the epidemiology of facial fractures in children and to analyze whether it has changed over time. STUDY DESIGN: Retrospective review of records of children aged < or = 15 years diagnosed for fracture during 2 10-year periods. RESULTS: A total of 378 children were diagnosed with fractures, 187 in 1980-1989 and 191 in 1993-2002. The proportion of children with mandibular fractures decreased by 13.6 percentage-points from the first period to the second, whereas the proportion of patients with midfacial fractures increased by 18.7 percentage-points. Assault as a causative factor increased by 5.5 percentage-points, almost exclusively among children aged 13-15 years, with a high percentage (23.5%). CONCLUSIONS: Recognition of a change in fracture patterns over time is probably due to the increased use of computerized tomographic scanning.

An Assessment of Trends in the Extent of Swidden in Southeast Asia

Swidden systems consisting of temporarily cultivated land and associated fallows often do not appear on land use maps or in statistical records. This is partly due to the fact that swidden is a diverse and dynamic land use system that is difficult to map and partly because of the practice of grouping land covers associated with swidden systems into land use or land cover categories that are not self-evidently linked to swiddening. Additionally, in many parts of Southeast Asia swidden systems have changed or are in the process of changing into other land use systems. This paper assesses the extent of swidden on the basis of regional and national sources for nine countries, and determines the pattern of changes of swidden on the basis of 151 cases culled from 67 articles. Findings include (1) a majority of the cases document swidden being replaced by other forms of agriculture or by other livelihood systems; (2) in cases where swiddening is still practiced, fallow lengths are usually, but not always, shorter; and (3) shortened fallow length does not necessarily indicate a trend away from swidden since it is observed that short fallow swidden is sometimes maintained along with other more intensive farming practices and not completely abandoned. The paper concludes that there is a surprising lack of conclusive data on the extent of swidden in Southeast Asia. In order to remedy this, methods are reviewed that may lead to more precise future assessments.