Is the prevalence of asthma declining? Systematic review of epidemiological studies

Risk for asthma in offspring of asthmatic mothers versus fathers: a meta-analysis

BACKGROUND

Many human epidemiologic studies demonstrate that maternal asthma confers greater risk of asthma to offspring than does paternal disease. However, a handful have shown the opposite. Given this disparity, a meta-analysis is necessary to determine the veracity and magnitude of the "maternal effect."

METHODOLOGY/PRINCIPAL FINDINGS

We screened the medical literature from 1966 to 2009 and performed a meta-analysis to compare the effect of maternal asthma vs. paternal asthma on offspring asthma susceptibility. Aggregating data from 33 studies, the odds ratio for asthma in children of asthmatic mothers compared with non-asthmatic mothers was significantly increased at 3.04 (95% confidence interval: 2.59-3.56). The corresponding odds ratio for asthma in children of asthmatic fathers was increased at 2.44 (2.14-2.79). When comparing the odds ratios, maternal asthma conferred greater risk of disease than did paternal asthma (3.04 vs. 2.44, p = 0.037). When analyzing the studies in which asthma was diagnosed by a physician the odds ratios were attenuated and no significant differences were observed (2.85 vs. 2.48, N = 18, p = 0.37). Similarly, no significant differences were observed between maternal and paternal odds ratios when analyzing the studies in which the patient population was 5 years or older (3.15 vs. 2.60, p = 0.14). However, in all cases the trend remained the same, that maternal asthma was a greater risk factor for asthma than paternal.

CONCLUSIONS/SIGNIFICANCE

The results show that maternal asthma increases offspring disease risk to a greater extent than paternal disease.

The Jamaica asthma and allergies national prevalence survey: rationale and methods

Background

Asthma is a significant public health problem in the Caribbean. Prevalence surveys using standardized measures of asthma provide valid prevalence estimates to facilitate regional and international comparisons and monitoring of trends. This paper describes methods used in the Jamaica Asthma and Allergies National Prevalence Survey, challenges associated with this survey and strategies used to overcome these challenges.

Methods/Design

An island wide, cross-sectional, community-based survey of asthma, asthma symptoms and allergies was done among adults and children using the European Community Respiratory Health Survey Questionnaire for adults and the International Study of Asthma and Allergies in Children. Stratified multi-stage cluster sampling was used to select 2, 163 adults aged 18 years and older and 2, 017 children aged 2-17 years for the survey. The Kish selection table was used to select one adult and one child per household. Data analysis accounted for sampling design and prevalence estimates were weighted to produce national estimates.

Discussion

The Jamaica Asthma and Allergies National Prevalence Survey is the first population- based survey in the Caribbean to determine the prevalence of asthma and allergies both in adults and children using standardized methods. With response rates exceeding 80% in both groups, this approach facilitated cost-effective gathering of high quality asthma prevalence data that will facilitate international and regional comparison and monitoring of asthma prevalence trends. Another unique feature of this study was the partnership with the Ministry of Health in Jamaica, which ensured the collection of data relevant for decision-making to facilitate the uptake of research evidence. The findings of this study will provide important data on the burden of asthma and allergies in Jamaica and contribute to evidence-informed planning of comprehensive asthma management and education programs.

Trends in the epidemiology of asthma in England: a national study of 333,294 patients

BACKGROUND

Observations in the UK at the end of the last century found increasing trends of asthma prevalence over time. However, it has been reported that the number of new cases of asthma presenting to general practice has declined, especially among younger children. Aim To study national trends in the epidemiology of asthma.

METHODS

A cross-sectional observation analysis was performed using the QRESEARCH database, which is one of the world's largest national aggregated health databases containing records from 422 English practices yielding 30 million patient-years of observation. Data was extracted on 333,294 individuals with a recorded diagnosis of asthma and calculated annual age-sex standardized incidence, lifetime period prevalence and asthma-related prescribing rates for each year from 2001-2005.

RESULTS

The incidence rate of asthma decreased in all patients (2001: 6.9 (95% confidence intervals [CI] 6.8-7.0); 2005: 5.2 (95% CI 5.1-5.3) per 1000 patient-years, p<0.001), but most particularly in children under 5 years of age (-38.4%) where a decrease in the lifetime prevalence of asthma (-34.3%) was also found. However, the lifetime prevalence rate of asthma for adults increased (15-44 years: 23.3%; 45-64 years: 27.7%; >65 years: 21.5%) with an estimated 5,658,900 (95% CI 5,639,700-5,678,200) or approximately one person in nine having being diagnosed with asthma in England. The number of asthma-related prescriptions also increased over the study period (17.1%), such that in 2005 an estimated 32,577,300 (95%CI 32,531,600-32,623,000) prescriptions were issued.

CONCLUSIONS

This large national study reveals that the rate of new diagnoses of asthma appears to have passed its peak; however, the number of adults with a lifetime asthma diagnosis continues to rise. Whether these trends are genuine or are a result of the introduction of incentives and guidelines to improve identification and recording of asthma or changing diagnostic trends is a question with important public health implications and one, therefore, that warrants detailed further enquiry.