What can lead to premature aging in humans?

Neurodegenerative diseases: when nerve cells perish

Because they are associated with aging processes, neurodegenerative diseases are considered to be an important medical challenge for the coming decades. Experts already estimate the number of people affected by dementia in Germany at around 1.5 million. In addition, an estimated 300,000 people in Germany are known to have Parkinson's disease.

In addition to Parkinson's disease and various forms of dementia, medicine knows a whole range of other neurodegenerative diseases. Some of these are age-related and some are not. Examples of neurodegenerative diseases that can also occur in young people are amyotrophic lateral sclerosis (ALS), Huntington's disease and the infectious prion disease "Creutzfeldt-Jacob".

According to estimates, the total number of patients in Germany with neurodegenerative diseases is likely to rise to three million or more by 2050 as a result of demographic change (German Center for Neurodegenerative Diseases).

Why the breakdown of nerve cells occurs

On the one hand, the nerve cells of the brain are very long-lived cells; on the other hand, they cannot regenerate, or only with difficulty, in the event of injuries. This is why neurodegenerative diseases are so fatal: the brain cannot easily replace those cells that die prematurely.

What ultimately leads to neurodegeneration differs from disease to disease and is often only partially known so far. In certain forms of Parkinson's disease or Creutzfeldt-Jacob's disease, for example, a genetic peculiarity leads to an accumulation of proteins in the nerve cells of the brain. These aggregates impair the cell function and lead to the death of the cells. In people with Huntington's disease, on the other hand, a very specific genetic sequence occurs in the genome much more frequently than in healthy people. The result is that the affected cells become more sensitive to external stimuli and die more easily.

In healthy people, the cells of the body have genetic programs which roughly determine how long the cell in question can live. The natural lifespan of cells in the body varies from tissue to tissue. Some cells only live a few days. Others make it for a few weeks. And still others stay with the body for a lifetime.

The place determines the symptoms

It is characteristic of neurodegenerative diseases that usually not the whole brain is affected, but different, often very precisely defined areas or cell types. For this reason, specialized doctors can determine exactly what kind of disease it is based on the clinical symptoms.

Parkinson's disease, for example, only affects nerve cells that produce the neurotransmitter dopamine. Dopamine is needed to control movement. The corresponding nerve cells have a coordinating function. Accordingly, Parkinson's patients appear stiff and slowed down in their movement sequences, or they show very characteristic movement patterns, such as rhythmic muscle twitching ("tremors"). The mental functions, on the other hand, are often retained.

Huntington's disease also affects nerve cells that are involved in controlling movement. In this case, the affected nerve cells produce the messenger substance glutamate. The affected people show sweeping movements that can act like a dance. Glutamate-producing nerve cells are also involved in higher mental abilities, so that the social behavior of those affected also changes.

In amyotrophic lateral sclerosis (ALS), on the other hand, so-called motor neurons perish selectively. These are nerve cells that connect the brain with the muscles. When motor neurons die, the brain can no longer “control” the muscles. The result is paralysis, which in the advanced stage of ALS can also affect the respiratory muscles.

German Center for Neurodegenerative Diseases

The German Center for Neurodegenerative Diseases e. V. (DZNE) researches the causes of disorders of the nervous system and develops strategies for prevention, therapy and care. It cooperates closely with universities, their clinics and non-university institutions. The DZNE is one of six centers for health research (DZG) set up by the Federal Ministry of Education and Research to combat the most important common diseases. Further information on the DZG can be found here.

Results of health research