- Studies indicate that getting less than six hours of sleep is linked to a higher risk of cognitive decline and high blood pressure.
- A recent study reveals that shorter sleep duration may combine with high blood pressure to heighten the risk of cognitive decline and brain aging.
- While these findings are correlational, they could pave the way for randomized studies to assess the effectiveness of treatments that alter sleep patterns or help manage blood pressure in preventing or slowing cognitive decline.
While some studies have identified a connection between insufficient sleep and an increased risk of cognitive impairment and dementia, other research has failed to find a similar link between sleep duration and cognitive function.
A recent study published in the Journal of the American Heart Association reveals that individuals with high blood pressure who also slept for shorter durations were more likely to exhibit poor cognitive function and higher levels of brain aging and injury markers. In contrast, those who had shorter sleep durations but normal blood pressure did not show these cognitive deficits or elevated markers of brain injury.
The study suggests that high blood pressure may play a key role in how sleep duration impacts cognitive health, potentially explaining the conflicting results in previous research.
This study also opens the door for early identification of individuals at risk for cognitive decline, as well as randomized trials investigating treatments that normalize sleep patterns and manage blood pressure to help prevent or delay cognitive decline.
Dr. Matthew Pase, the study’s author and an associate professor at Monash University, shared with Medical News Today:
“The findings highlight the importance of maintaining healthy blood pressure and ensuring adequate sleep to support brain health in old age. Doctors should be vigilant in monitoring and managing patients’ blood pressure levels. Additionally, the medical community is increasingly recognizing the significance of good sleep, and it should now be seen as an integral part of a healthy lifestyle.”
The amount of sleep a person requires can vary
One of the study’s strengths was its large sample size, but due to its observational design, it cannot establish a causal relationship between sleep duration and cognitive health.
The sleep study was conducted over a single night, meaning the data on sleep duration may not accurately reflect long-term sleep patterns. Since blood pressure typically decreases by 10% at sleep onset, shorter sleep duration could prevent this drop. However, blood pressure was measured during the daytime, so the potential impact of sleep patterns on the blood pressure drop at sleep onset may have been overlooked.
Additionally, Dr. Christopher Berg, a board-certified cardiologist at Memorial Care Heart and Vascular Institute, pointed out some limitations of the study. He stated, “The strength of their findings was unimpressive. For example, they assessed cognitive function with six tests, only one of which showed a significant relationship with sleep duration in individuals with hypertension.”
He continued, “They also examined six MRI-based parameters, but again, only one showed an association with sleep duration in those with hypertension. The meaningful correlation between these parameters and actual cognitive performance, or their relevance to dementia risk, remains uncertain, as does the extent to which these findings can be extrapolated.”
Dr. Berg also noted that individual sleep needs can vary significantly. “The idea of a universal recommendation‘ everyone needs X hours of sleep’ is not strongly supported by the literature and doesn’t seem to hold up in practice. Nevertheless, this study reinforces the general recommendation that adequate sleep is important for both mental and physical health, particularly for individuals with hypertension,” he said.
Associating reduced sleep with cognitive impairments.
The study involved 682 participants aged 40 and older, who were part of the Framingham Health Study, a multi-generational longitudinal research project focused on identifying risk factors for cardiovascular diseases. Only participants without dementia or a history of stroke were included.
Sleep data was collected through a questionnaire and a home-based sleep study (polysomnography). Additionally, participants’ daytime blood pressure was measured during the sleep assessment. Approximately 3.3 years later, participants underwent cognitive evaluations and MRI scans to examine changes in brain structure.
The researchers found no significant association between sleep duration and cognitive function or brain imaging markers, except for gray matter volume. In this case, individuals who self-reported shorter sleep duration had larger gray matter volumes.
When the researchers analyzed the effects of sleep duration on cognitive health, separating participants into those with normal and high blood pressure, they discovered that sleep duration impacted cognitive function and brain imaging biomarkers only in those with high blood pressure.
