Trends in worldwide asthma prevalence.

This review of trends in worldwide asthma prevalence starts with defining how asthma prevalence is measured in populations and how it is analysed. Four population studies of asthma across at least two regions are described: European Community Respiratory Health Survey (ECRHS), the International Study of Wheezing in Infants (EISL), the International Study of Asthma and Allergies in Childhood (ISAAC) and the World Health Survey (WHS). Two of these (ISAAC and WHS) covered all the regions of the world; each using its own standardised questionnaire-based methodology with cross-sectional study design, suitable for large populations. EISL (2005 and 2012) and ISAAC (1996-1997 and 2002-2003) have undertaken a second cross-sectional population survey from which trends are available: EISL in three centres in two countries; ISAAC 106 centres in 56 countries (13-14 year olds) and 66 centres in 37 countries (6-7 year olds). Key results from these studies are presented. Unfortunately, there is no new worldwide data outside of EISL since 2003. Global Burden of Disease estimates of asthma prevalence have varied greatly. Recent reliable worldwide data on asthma prevalence and trends is needed; the Global Asthma Network Phase I will provide this in 2021.

The Global Asthma Network rationale and methods for Phase I global surveillance: prevalence, severity, management and risk factors.

The Global Asthma Network (GAN), established in 2012, followed the International Study of Asthma and Allergies in Childhood (ISAAC). ISAAC Phase One involved over 700 000 adolescents and children from 156 centres in 56 countries; it found marked worldwide variation in symptom prevalence of asthma, rhinitis and eczema that was not explained by the current understanding of these diseases; ISAAC Phase Three involved over 1 187 496 adolescents and children (237 centres in 98 countries). It found that asthma symptom prevalence was increasing in many locations especially in low- and middle-income countries where severity was also high, and identified several environmental factors that required further investigation.GAN Phase I, described in this article, builds on the ISAAC findings by collecting further information on asthma, rhinitis and eczema prevalence, severity, diagnoses, asthma emergency room visits, hospital admissions, management and use of asthma essential medicines. The subjects will be the same age groups as ISAAC, and their parents. In this first global monitoring of asthma in children and adults since 2003, further evidence will be obtained to understand asthma, management practices and risk factors, leading to further recognition that asthma is an important non-communicable disease and to reduce its global burden.

Genome-wide association studies may be misinterpreted: genes versus heritability.

Much of the literature on genome-wide association studies (GWAS) is based on the premise that an important proportion of common diseases is heritable and that this proportion is likely to be due to genetic variants detectable with extensive scans of the DNA. Heritability is estimated from family studies, including twin studies and is based on the comparison of the variation in disease among different members of particular families. Since there is a wide gap between the population variation in disease explained by the results of GWAS (usually <10% for common diseases) and estimates of heritability (often >50%), the question arises as to how to explain these differences. However, the premise for this question is based on two sources of misunderstanding: (i) confusion between variation and causation and (ii) confusion between heritability and genetic determination. As we show with a number of examples, variation is not causation and heritability is not genetic determination. Therefore, heritability studies do not provide valid estimates of the proportion of disease cases that are attributable to genetic factors. Such estimates in turn cannot be used to estimate the proportion of cases that are due to environmental factors.

Developing a general population job-exposure matrix in the absence of sufficient exposure monitoring data.

In New Zealand, there is a need for a comprehensive and accessible database with national occupational exposure information, such as a general population job-exposure matrix (GPJEM). However, few New Zealand-specific exposure data exist that could be used to construct such a GPJEM. Here, we present the methods used to develop a GPJEM for New Zealand (NZJEM), by combining GPJEMs from other countries with New Zealand-specific exposure information, using wood dust as an example to illustrate this process. The assessments of GPJEMs from other countries were made available to a New Zealand expert in occupational wood dust exposure, who then provided a preliminary NZJEM assessment (including the percentage exposed and the level of exposure for each occupation). Where possible, this assessment was based on New Zealand exposure measurements. In the next step, information from a nationwide workplace exposure survey of 3000 members of the New Zealand workforce was used to finalize the NZJEM assessments. The final NZJEM listed 104 of the 956 New Zealand occupational codes as exposed to wood dust. The percentage of workers exposed within an occupation ranged from 5% (e.g. boiler attendants) to 100% (e.g. cabinet makers). The level of exposure ranged from 0.05 mg m(-3) (e.g. electricians) to 3 mg m(-3) (e.g. carpenters). Of these assessments, 23% were mainly based on New Zealand exposure data, 37% on overseas GPJEMs and exposure data, and for 40% the national survey data served as the main source of information for the expert assessment. Combining the NZJEM assessments with national employment statistics indicated that 5.6% of the New Zealand workforce is occupationally exposed to wood dust, corresponding to a total of 97 000 workers (86% male and 14% female). Construction-related occupations included the largest number of exposed workers.

The Tasmanian Epilepsy Register--a community-based cohort. Background and methodology for patient recruitment from the Australian national prescription database.

BACKGROUND/AIMS: Centralized prescription databases may provide an efficient mechanism for recruitment of community-treated disease. METHODS: The Australian federal government agency, the Health Insurance Commission (HIC), invited patients to participate in the Tasmanian Epilepsy Register (TER). Eligible patients included those who received at least one anticonvulsant above a 'reportable' price threshold between July 1, 2001 and June 30, 2002. Patients were asked to disclose their medical indication for anticonvulsant treatment with additional demographic and prescription information obtained from the HIC. RESULTS: 7,541 were eligible for recruitment. After two mail invitations over 6 months, 3,375 (46.6%) had responded, but TER enrollment amongst those indicating treatment for epilepsy was 1,180 (78.3%). TER participants were more likely to obtain their prescriptions exclusively from their general practitioner (70.9%) or from combined sources (19.1%) rather than from pediatrician (4.2%), neurologist (1.4%) or general physician (1.0%) sources. Patients were more likely to respond with increasing age (linear trend p < 0.001), when from a higher socioeconomic area (linear trend p < 0.001), or if their prescription was obtained from a neurologist (p < 0.001). CONCLUSION: The national Australian prescription database represents community-treated epilepsy and provides an effective and efficient method for patient recruitment for clinical epidemiological research.