People who grew up surrounded by dogs in an urban environment and those who were breastfed and grew up with siblings may have one thing in common: asthma, according to a study by 20 researchers. The latter, specialized in different disciplines, have concluded that four specific combinations of exposure are more associated with asthma than the others.
His multidisciplinary study, carried out on almost 21,000 French people, was published in the American journal of respiratory and critical care medicine. Four aspects of the lives of the people studied were taken into account: socioeconomic factors, the living environment of these people at the time of the study and at the beginning of their life, but also their way of life.
Three situations in children, one in adults
The first of the combinations that is particularly likely to be associated with asthma is “exposure to heavy passive smoking during childhood” (from birth to age six) supported by living with dogs.
A paradox, when two previous studies concluded that a childhood surrounded by dogs could have benefits in preventing the risk of asthma. According to the latter, benefits were even seen in children exposed to dogs when they were still fetuses.
Another combination of factors found more than others in people with asthma: having so-called “unfavorable” delivery profiles, that is, delivering prematurely (before the eighth month of pregnancy) or by caesarean section, then spending a long time in a nursery in a urban environment. The first factor can lead to altered functioning of the body compared to normal, while the second coincides with a deterioration in the quality of the air breathed.
The last combination in children consists of belonging to a family of at least three people and having been breastfed. This last factor had also been pointed out as a preventive of asthma by a previous study, but only for people with exclusive breastfeeding (without bottles) and in families with no history of respiratory disorders.
In adults, unbalanced diet (which in the study most often leads to overweight) associated with smoking is the most correlated with asthma. The study indicates, however, that diet influences asthma risk less than body mass index (BMI), in this case being overweight.
The study also recalls that the number of asthma cases is constantly increasing in Western countries. In France, about 1,000 people die each year from asthma.
A “causal link” has not been established at this stage
If these associations of factors are more present in people with asthma, the study does not say that their presence is a mechanical cause of the disease. An important nuance not to jump to conclusions.
We will perform further analyzes to assess the existence of causal links. If this is the case, we can imagine the development of disease prevention programs that will be better targeted”, explains Valérie Siroux, director of the study.
This work also represents the first approach to analyze the link between the associations of factors and the development of asthma. This method could be reused to study other respiratory conditions in the future, in a search for coincidences before trying to establish cause-and-effect links.
Source: BFM TV
