A groundbreaking study conducted by researchers from the UK, Germany, and Australia has linked obstructive sleep apnoea (OSA) to early cognitive decline, even in patients who are otherwise healthy and not obese. OSA is a potentially dangerous condition that affects an estimated 1 billion adults worldwide, with up to 80% of sufferers remaining undiagnosed.
Dr Ivana Rosenzweig, a neuropsychiatrist who heads the Sleep and Brain Plasticity Centre at King’s College London, and the lead author of the study, said, “We show poorer executive functioning and visuospatial memory and deficits in vigilance, sustained attention, and psychomotor and impulse control in men with OSA. Most of these deficits had previously been ascribed to co-morbidities. We also demonstrated for the first time that OSA can cause significant deficits in social cognition.”
The study, published in Frontiers in Sleep, involved 27 men aged 35–70 with a new diagnosis of mild to severe OSA but without any co-morbidities, as well as a control group of seven age-, BMI-, and education-matched men without OSA. These participants were selected because most OSA sufferers have co-morbidities such as cardiovascular and metabolic disease, stroke, diabetes, chronic systemic inflammation, or depression, making it difficult to determine the direct effects of OSA on cognitive function.
Participants’ sleep was monitored using electroencephalography (EEG) to measure brain waves, while blood oxygen levels, heart rate, breathing, and eye and leg movements were also tracked. The researchers tested the subjects’ cognitive function with the Cambridge Neuropsychological Test Automated Battery (CANTAB).
The results revealed that patients with severe OSA had poorer vigilance, executive functioning, short-term visual recognition memory, and social and emotion recognition than the matched controls. Patients with mild OSA performed better in these domains than patients with severe OSA but worse than the controls.
Dr Rosenzweig explained the potential mechanisms behind these findings: “This complex interplay is still poorly understood, but it’s likely that these lead to widespread neuroanatomical and structural changes in the brain and associated functional cognitive and emotional deficits.”
The study is a significant step in understanding the impact of OSA on cognitive function, as it provides proof of concept that OSA itself can lead to cognitive deficits. However, the role of co-morbidities remains unclear.
Dr Rosenzweig elaborated on this point: “Our findings suggest that co-morbidities likely worsen and perpetuate any cognitive deficits caused directly by OSA itself. What remains to be clarified in future studies is whether co-morbidities have an additive or synergistic effect on the latter deficits, and whether there is a difference in brain circuitry in OSA patients with or without co-morbidities.”
The implications of this study are significant, as OSA affects a large portion of the adult population, particularly men in middle or old age. Major risk factors for OSA include obesity, smoking, chronic nasal blockage, high blood pressure, and being male.
Early intervention and treatment for OSA could potentially reduce or even prevent cognitive decline in sufferers. The condition is characterised by symptoms such as restless sleep, loud snoring, daytime sleepiness, and prolonged morning headaches, which can be highly debilitating for patients and their partners.
This research highlights the importance of raising awareness about OSA, its potential consequences on cognitive function, and the need for further studies to explore the complex relationship between OSA, co-morbidities, and cognitive decline.
