Islamabad - A research suggests that Alzheimer’s disease is yet another condition that may be caused by sleep disorders.

Co-author Barbara B Bendlin of the University of Wisconsin-Madison explains the motivation for the study, saying, “Previous evidence has shown that sleep may influence the development or progression of Alzheimer’s disease in various ways.”

“For example, disrupted sleep or lack of sleep may lead to amyloid plaque build-up because the brain’s clearance system kicks into action during sleep. Our study looked not only for amyloid but for other biological markers in the spinal fluid as well.”

Biological markers for Alzheimer’s disease include signs of amyloid and tau protein build-up. Amyloid and tau are “sticky” proteins produced in excess in the brains of people with Alzheimer’s disease.

The former builds up into plaques, while the latter forms tangles. These are formations that either block the communication between neurons or obstruct the transport of nutrients to nerve cells, eventually leading to neurodegeneration.

Upon analysis, participants’ cerebrospinal fluid showed “signs of amyloid, tau, and brain cell damage and inflammation.”

The study therefore revealed that people who reported being sleepy during the day, having poor sleep quality, or experiencing other sleep problems, had more biological markers for Alzheimer’s disease in their spinal fluid compared with people who did not report having trouble sleeping.

The results remained even when the researchers adjusted for potential confounders, including the use of sleep medication, education, depression, and body mass index.

However, the authors note that not all sleep disorders correlated with signs of Alzheimer’s. For instance, the researchers found no association between spinal fluid biological markers and obstructive sleep apnea.

“It’s important to identify modifiable risk factors for Alzheimer’s given that [...] delaying [its] onset in people by a mere 5 years could reduce the number of cases we see in the next 30 years by 5.7 million.”

Bendlin says the study did not address causality, so “it’s still unclear if sleep may affect the development of the disease or if the disease affects the quality of sleep. More research is needed to further define the relationship between sleep and these biomarkers.”

Bendlin concludes, “It may be possible that early intervention for people at risk of Alzheimer’s disease may prevent or delay the onset of the disease.”

Another study suggests that middle-aged adults who experience a moderate to severe traumatic brain injury (TBI) may be at significantly greater risk of developing dementia in later life. TBI is defined as a blow, bump, or jolt to the head that causes damage to the brain.

Study co-author Dr Rahul Raj of the University of Helsinki in Finland and colleagues sought to investigate this association further.

When the team accounted for numerous confounding factors - including age, sex, education, and socioeconomic status - the researchers found that participants who experienced a moderate to severe TBI were 90 per cent more likely to be diagnosed with dementia than those who had a mild TBI.

Dementia risk was highest for adults whose moderate to severe TBI occurred between the ages of 41 and 50, the team reports, and middle-aged men were more likely to develop the neurodegenerative disease than middle-aged women.

“It seems that the risk for developing dementia after TBI is the highest among middle-aged men,” notes Dr Raj.

“The more severe the TBI, the higher the risk for subsequent dementia. While previous studies have identified good education and high socioeconomic status as protective factors against dementia, we did not discover a similar effect among TBI survivors.”

The researchers found no link between TBI and increased risk of Parkinson’s or ALS.

Dr Raj and colleagues believe that their findings indicate that TBI sparks a process that leads to dementia later in life, but further studies are needed to pinpoint the exact mechanisms behind this process.

In the meantime, the team hopes that the study helps to encourage longer-term monitoring of adults who have a TBI, in both clinical and research settings.

“It is a tragedy when an adult of working age develops dementia after recovering from a brain injury, not just for the patient and their families, but it also negatively impacts the whole society,” says Dr Raj.

“In the future, it will be increasingly important to prevent TBIs and to develop rehabilitation and long-term monitoring for TBI patients.”