Atopy is associated with asthma in adults living in rural and urban southwestern Nigeria

Parasites and allergy: Observations from Africa

Population studies from the African continent have observed a marked increase in the prevalence of allergy‐related diseases over the past few decades, but the cause of this rise is not fully understood. The most investigated potential risk factor has been the relationship between exposure to helminths and allergy‐related outcomes. Immunologically, parallels exist between responses to helminths and to allergens as both are associated with elevated levels of immunoglobulin E, increased numbers of T helper 2 cells and other immune cells. However, epidemiological studies from the African continent have found inconsistent results. In this review, observations from population studies carried out in Africa over the last decade that focus on the relationship between helminth infections and allergy‐related outcomes are examined. How these findings advance our understanding of the complex interactions between helminths and allergies at the population level is also explored as well as some of the underlying immune mechanisms involved. This knowledge is important for better diagnosis, treatment and prevention of allergy‐related diseases and has wider global significance.

Low prevalence of asthma in sub Saharan Africa: a cross sectional community survey in a suburban Nigerian town

BACKGROUND

Asthma remains an important cause of morbidity and mortality, especially in developing countries but the prevalence in Nigeria is not well described.

METHODS

Using the European Community Respiratory Health Survey (ECRHS) standard screening questionnaire and asthma criteria, we recruited a representative sample of adults resident in a suburban community in Nigeria through a stratified three-stage cluster sampling technique.

RESULTS

Out of a total of 3590 individuals contacted, 2310 responded and provided completed data (62.8% female). The prevalence of respiratory symptoms ranged from 0.4% (95% CI: 0.1-0.6) to 9.1% (95% CI: 7.6-10.6). Apart from nasal allergies, the most frequently reported symptoms were 'woken up by an attack of breathlessness at any time in the last 12 months' (2.4%, 95% CI: 1.8-3.0) and 'woken up by an attack of cough at any time in the last 12 months' (2.9%, 95% CI: 2.0-3.7). The combined proportion of respondents reporting previous asthma attack or currently taking asthma medication within the preceding 12 months (diagnosed asthma) was 1.5%, 95% CI: 1.0-2.0. The proportion with 'probable asthma' based on ECRHS criteria of any three symptoms of asthma (woken up by an attack of breathlessness or previous asthma attack or currently taking asthma medication within the preceding 12 months) was 3.1%, 95% CI: 2.0-4.3 for men and 3.3%, 95% CI: 2.4-4.2 for women.

CONCLUSION

The prevalence of asthma in this suburban Nigerian population is low. Determinants of adult asthma distribution in low-income setting need further clarification.

Symptom prevalence and risk factors for asthma at the rural regions of Denizli, Turkey

OBJECTIVE

This study was conducted using a standardised method (ECRHS) to identify the prevalence of asthma symptoms and risk factors in adults who lives in the rural regions of Denizli province.

METHODS

This study was designed as a cross-sectional study to investigate the prevalence of asthma and asthma symptoms in adults older than 18 years old, around the rural regions of Denizli. Data were collected by personal interview and filling in questionnaires between July 2009 and September 2009.

RESULTS

A total of 1,343 individuals were enrolled. Prevalence of current asthma was 5.9%, having an asthma-like symptom was 34.0% and allergic rhinitis was 2.5%. Most common asthma symptoms were woken by an attack of breathlessness (20.5%, n=275), woken by attack of cough (19.9%, n=267) and wheezing (12.7%, n=171).

CONCLUSIONS

Asthma is an important disease that may occur not only in cities but also at country sides. In rural areas risk factors for asthma and asthma-like symptoms compared to urban areas may show some differences.

Allergy sensitization and asthma among 13-14 year old school children in Nigeria

BACKGROUND

The prevalence of asthma and role of atopy in asthma among children has not been clearly defined in Nigeria.

OBJECTIVE

To determine the prevalence of asthma and investigate risk factors related to allergy sensitization among urban and rural school children in southwest Nigeria.

METHODS

Validated ISAAC questionnaire was administered to 1736 high school children in randomly selected schools in rural and urban communities. Identified asthma cases were matched to controls. Allergy skin tests, blood eosinophil count, serum IgE and stool examination for parasites were performed. Dust samples from homes were also collected and analyzed for allergens.

RESULTS

The prevalence of asthma was 7.5% (95% CI 6.0 to 9.2%) and 8% (95% CI 6.0-10.4%) in the rural and urban communities respectively . Risk factors for asthma included cigarette-smoking, cats in the home and family size. Eosinophil count (109/L) was elevated in asthmatics [0.70 (95% CI 0.48-1.11) vs. 0.32 (95% CI 0.19-0.69); p<0.01], but IgE levels were similar between the two groups (298±229 IU/mL vs. 288±257; p=0.97). Positive skin tests to cat hair, cockroach, mango blossom and mouse epithelium were more frequent in asthmatics than in healthy controls, especially in the rural communities. There was no correlation between allergens in dust collected from homes and skin test reactivity.

CONCLUSION

Asthma prevalence is similar in rural and urban children in Southwest Nigeria and atopy with elevated IgE was not observed to be a major factor for asthma in our cohort of children in both communities.

Urban vs. rural factors that affect adult asthma

In this review, our aim was to examine the influence of geographic variations on asthma prevalence and morbidity among adults, which is important for improving our understanding, identifying the burden, and for developing and implementing interventions aimed at reducing asthma morbidity. Asthma is a complex inflammatory disease of multifactorial origin, and is influenced by both environmental and genetic factors. The disparities in asthma prevalence and morbidity among the world's geographic locations are more likely to be associated with environmental exposures than genetic differences. In writing this article, we found that the indoor factors most consistently associated with asthma and asthma-related symptoms in adults included fuel combustion, mold growth, and environmental tobacco smoke in both urban and rural areas. Asthma and asthma-related symptoms occurred more frequently in urban than in rural areas, and that difference correlated with environmental risk exposures, SES, and healthcare access. Environmental risk factors to which urban adults were more frequently exposed than rural adults were dust mites,high levels of vehicle emissions, and a westernized lifestyle.Exposure to indoor biological contaminants in the urban environment is common.The main risk factors for developing asthma in urban areas are atopy and allergy to house dust mites, followed by allergens from animal dander. House dust mite exposure may potentially explain differences in diagnosis of asthma prevalence and morbidity among adults in urban vs. rural areas. In addition, the prevalence of asthma morbidity increases with urbanization. High levels of vehicle emissions,Western lifestyles and degree of urbanization itself, may affect outdoor and thereby indoor air quality. In urban areas, biomass fuels have been widely replaced by cleaner energy sources at home, such as gas and electricity, but in most developing countries, coal is still a major source of fuel for cooking and heating, particularly in winter. Moreover, exposure to ETS is common at home or at work in urban areas.There is evidence that asthma prevalence and morbidity is less common in rural than in urban areas. The possible reasons are that rural residents are exposed early in life to stables and to farm milk production, and such exposures are protective against developing asthma morbidity. Even so, asthma morbidity is disproportionately high among poor inner-city residents and in rural populations. A higher proportion of adult residents of nonmetropolitan areas were characterized as follows:aged 55 years or older, no previous college admission, low household income, no health insurance coverage, and could not see a doctor due to healthcare service availability, etc. In rural areas, biomass fuels meet more than 70% of the rural energy needs. Progress in adopting modern energy sources in rural areas has been slow. The most direct health impact comes from household energy use among the poor, who depend almost entirely on burning biomass fuels in simple cooking devices that are placed in inadequately ventilated spaces. Prospective studies are needed to assess the long-term effects of biomass smoke on lung health among adults in rural areas.Geographic differences in asthma susceptibility exist around the world. The reason for the differences in asthma prevalence in rural and urban areas may be due to the fact that populations have different lifestyles and cultures, as well as different environmental exposures and different genetic backgrounds. Identifying geographic disparities in asthma hospitalizations is critical to implementing prevention strategies,reducing morbidity, and improving healthcare financing for clinical asthma treatment. Although evidence shows that differences in the prevalence of asthma do exist between urban and rural dwellers in many parts of the world, including in developed countries, data are inadequate to evaluate the extent to which different pollutant exposures contribute to asthma morbidity and severity of asthma between urban and rural areas.