What many have long suspected, researchers at the Universities of Zurich (UZH) and Lausanne (UNIL) have already scientifically proven by a study: We do not make our children, if we protect them from everything, especially from anything that might be sick. A person's immune system is formed during childhood through "training."
In addition, the so-called hygiene hypothesis provides a very considered perspective. Therefore, better hygiene, changes in agriculture and urbanization are responsible for our immune system coming into contact with some microbes less often or later in life, making us more susceptible to diseases. Thus, both chronic inflammatory diseases, allergies and mental illnesses, such as depression, would increase.
But not only hygiene, also childhood-experienced traumas and allergies can trigger chronic inflammatory diseases and mental disorders in adult life. Swiss scientists have been able to prove this through five groups, in which they identified the early programming of the immune system.
One in five have a very resistant immune system
The researchers based their study on the hygiene hypothesis and examined the epidemiological data of just under 5,000 people from the mid-twentieth century. They focused on the coincidence of allergies, viral and bacterial diseases and psychosocial stress in childhood. The scientists identified five distinct groups of early disease patterns, which they characterized using biological markers (white blood cells, inflammatory markers). In a second moment, they linked them to inflammatory mental disorders and chronic adults.
The result showed that 60% of the individuals examined had a discrete and "neutral" immune system and that their childhood load was comparatively low. 20 percent of the individuals showed a particularly resilient "resilient" immune system. "Even typical symptoms and unavoidable diseases of childhood, such as measles, mumps, or rubella, have manifested significantly less in this group than in the neutral group," the researchers write.
In contrast to the two largest and resilient groups, there were also three smaller groups: 7% of the people, the "atopic" group, had various allergic diseases. The "mixed" group (about 9%) had all kinds of unique allergic diseases. She suffered from, for example, allergies to drugs, bacterial and rash-related problems such as scarlet fever, whooping cough, or rubella. The smallest of the five groups (about 5%) consisted of people traumatized during childhood. These people were more susceptible to allergic diseases, but were relatively resistant to viral diseases typical of childhood.
Confirmed hygiene hypothesis
An interesting and important point of the study is that neutral and resilient groups are more likely to be in more advanced age groups than younger ones. In contrast, the atopic group, ie those more susceptible to hypersensitivity reactions, increased in younger age groups. "Our study confirms the hypothesis of hygiene, but at the same time goes beyond," says the first author Vladeta Ajdacic-Gross, UZH.
Differences between groups would also manifest themselves in terms of later health. People in the resilient group are better protected in adulthood, not only from chronic inflammatory diseases, but also from mental complaints. Members of the atopic and mixed group are physically and mentally at increased risk of disease as adults. In the traumatized group, people were more susceptible to mental illness in adulthood, and women also had a greater risk of developing chronic inflammatory diseases.
"The results indicate that the immune system functions as a hub between somatic and mental processes," explains Ajdacic-Gross. "They help us understand why many people without psychosocial pre-charge of mental health problems are picked up and why traumatized people are prone to chronic inflammatory diseases."
The results of the study "A step beyond hygiene hypothesis – immunomediated classes determined in a population-based study" were published in the online journal BMC Medicine published.
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