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To what extent environmental factors may lead to health effects in children will depend on certain personal circumstances such as genetic background, gender, age, ethnicity, and social conditions. More...
Pulmonary diseases in children may have a genetic basis. Usually several genes are involved, except in the case of cystic fibrosis, which results from a change in a single gene.
In the case of asthma a genetic predisposition is usually necessary for the onset of the disease, but environmental factors are also involved. Children of affected parents are two to three times more likely to develop asthma. However, in addition to genetic factors, environmental factors may also be important since the increased prevalence of asthma and allergy cannot be explained by genetic factors alone.
Environmental and genetic factors often interact. Therefore, researchers are interested in identifying environmental factors, such as exposure to tobacco smoke and air pollution, that may contribute to causing or triggering asthma, allergies, or other respiratory diseases. More...
In early childhood, about twice as many boys suffer from asthma than girls do. During adolescence this ratio is reversed and a larger number of girls are affected. The timing of this gender reversal suggests that sex hormones play a certain role in asthma. More...
Many diseases that appear during childhood or adult life may have their origins in very early stages of life. In humans, the development of the lungs occurs during development in the womb or shortly after birth, and there seems to be a link between low birth weight and respiratory problems later in life.
It has been observed that both serious respiratory infections in childhood and early exposure to adverse environmental factors may result in respiratory problems in adults. For instance, exposure to environmental tobacco smoke after birth can cause respiratory problems in children. However, if a mother exposes her unborn child to tobacco smoke by smoking during pregnancy, this can lead to even longer lasting effects.
Children have a higher breathing rate than adults. This means that children breathe in more air relative to their body weight compared to adults and are thus more exposed to environmental factors, such as airborne particulate matter. More...
In developing countries, respiratory infections, often combined with malnutrition, are one of the most common causes of death in children under 5 years of age. Lack of access to clean water and sanitation, malnutrition and poor access to medical services can foster the development of infectious diseases.
In developed countries, such as the United Kingdom, adults and children of lower socio-economic status have also been demonstrated to be at higher risk of respiratory infections. This may be due to crowding, increased exposure to infectious agents or reduced immunity related to a bad diet. More...
Living conditions can modify the effect of both genetic and environmental factors. Thus in theory, improving living conditions is a powerful way to prevent disease. More...
3.5.1 In Western Europe, there has been a steep decrease in the prevalence of severe infectious diseases such as tuberculosis. Worldwide, pneumonia is the respiratory disease that causes the largest number of deaths in children, and is linked both to infections and living conditions. More...
3.5.2 Asthma and allergies have become more and more frequent in Western Europe. One explanation for this increase is the “hygiene hypothesis” which assumes that infections in early childhood may prevent the development of allergic diseases. The human immune system uses two complementary types of biological responses to infections. When one part of the immune system lacks practice fighting bacteria and viruses, perhaps from an overly sanitary lifestyle, the other part can overreact to harmless substances like pollen, causing an allergic reaction.
Other possible explanations for the increase in asthma and allergies are changes in diet, such as a higher salt intake, a lower intake of certain vitamins and a lower consumption of fish that contains omega-3 fatty acids, that may also contribute to the development of asthma.
In addition, factors affecting the development of the fetus may lead to a greater risk of asthma later in life. For instance, there is a higher number of children suffering from asthma among those who were very small at birth or those who are born from older mothers. Moreover, if a mother smokes during pregnancy it affects on her child’s birthweight and early childhood respiratory health. However, it is not clear if this increases the risks of developing asthma and allergies in the longer term. In contrast, breast feeding for at least 6 months can protect children against respiratory problems in early life, but longer-term benefits for asthma and allergies are not clear. More...
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