If the memory has become worse, many think of the beginning of dementia. However, the fear is often unfounded. It is different if certain proteins are also detectable in the cerebrospinal fluid.
Many people experience subjective cognitive impairment. One becomes more forgetful, can no longer find the right word or the attention span becomes shorter. Older people in particular are familiar with the feeling that the head is sagging. If doctors are then unable to determine any reduction in mental performance using objective test methods, this is referred to in medicine as “subjective cognitive impairment”. The abbreviation SCD is derived from the English technical term “Subjective Cognitive Decline”.
Subjective cognitive impairments do not mean anything
Scientists from the German Center for Neurodegenerative Diseases (DZNE) have now investigated the phenomenon. According to this, many people with subjective cognitive impairments do not experience a progressive loss of cognitive performance. That’s the reassuring news. “SCD is a risk factor, but not a clear warning signal for later dementia,” says DZNE researcher Prof. Frank Jessen, director of the Psychiatric Clinic and at the University Hospital in Cologne.
Study examines the interaction with proteins in the cerebrospinal fluid
But the researchers found something else. It is about protein deposits in the brain, so-called plaques. “If, in addition to SCD, there is also evidence that certain proteins accumulate in the brain, then taken together this is a strong suspicion of developing Alzheimer’s disease,” reports Jessen.
In a study, the DZNE researchers examined 400 people with subjective cognitive impairments at the start of the study and around 300 people with measurable cognitive impairments – including symptoms of dementia due to Alzheimer’s disease. More than 200 adults whose cognitive performance was within the normal range and who did not have SCD at the start of the study served as a control group. The study participants were on average around 70 years old.
Among other things, cerebrospinal fluid was taken from the study participants in order to measure the protein beta-amyloid. The protein accumulates in the brain during Alzheimer’s disease. According to the report, 83 subjects with SCD and 25 subjects in the control group had amyloid beta above the threshold, meaning these subjects were amyloid positive.
The combination of SCD and beta amyloid is problematic
“Beta-amyloid deposition, like SCD, is a risk factor for Alzheimer’s. Considered in isolation, however, neither phenomenon is a clear indicator of a disease. But the picture becomes clearer, as our study proves, if you look at these phenomena together and over a longer period of time,” says Jessen.
Measurable cognitive deficits developed during the study period primarily in study participants who both complained about subjective cognitive impairments and were amyloid-positive. Those affected also showed a smaller hippocampus in the MRI, which is an indication of the loss of brain mass.
“If you add up all the findings, including the data from those subjects who already had measurable cognitive deficits at the start of the study, then we see the combination of SCD and amyloid-positive status as a strong indicator of early-stage Alzheimer’s disease,” says Jessen. The combination roughly corresponds to stage 2, which is the time before measurable symptoms of Alzheimer’s disease appear for the first time.
The results of the study “Subjective cognitive decline and stage 2 of Alzheimer’s disease in patients from memory centers” have been published in the journal Alzheimer’s & Dementia.