Cognitive dysfunction in patients with obstructive sleep apnea (OSA): partial reversibility after continuous positive airway pressure (CPAP)
Introduction
Obstructive sleep apnea (OSA) is characterized by repeated episodes of upper airway obstruction during sleep, which result in intermittent hypoxemia and disruption of the normal sleep pattern. Most frequent symptoms reported by patients are excessive daytime sleepiness (EDS), memory impairment, and lack of concentration 5., 19., 20., 21.. Because of the negative effect of cognitive dysfunction on daily life, in the last few years there has been an emergent interest in the neuropsychological evaluation of OSA patients.
Several studies in OSA demonstrated the presence of cognitive deficits concerning memory 5., 6., 13., 31., 37., attention 5., 14., 15., 21., 29., 38., executive functions, and motor abilities 5., 6., 13., 21., 31..
Moreover, it has been demonstrated that continuous positive airway pressure treatment (CPAP), which improves the respiratory pattern of OSA patients 11., 12., 39., 41., results in an improvement of the cognitive deficits. A number of studies showed an improvement of selected neurocognitive impairments after 4–6 months of treatment 3., 11., 23., 24., 25., 28.. However, the results are difficult to interpret, because the severity of OSA, the degree of impairment, and the specific areas of cognitive improvements varied greatly in the different investigations. The majority of studies have evaluated the CPAP effects after several months of treatment. In just a few cases, the effects have been analyzed after a very short period (one or two nights of therapy) showing conflicting results 25., 35., 41., 42., 43..
The aims of this study were to assess the cognitive status in a selected sample of OSA patients, and to evaluate the effect of CPAP after both a short (15 days) and a long (4 months) period of treatment.
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Subjects
Twenty-tree patients, 2 females and 21 males were included in the OSA group (age: 56.5±6.1 years; education level: 10.9±5.1 years; Body mass index (BMI): 33.45±5.64). Inclusion criteria were: (a) diagnosis of severe OSA (apnea/hypoapnea index (AHI)>40); (b) age between 45 and 65 years; and (c) complaint of excessive daytime somnolence for at least 1 year.
Twenty-three healthy subjects, 4 females and 19 males, were included in the control group (age: 55.8±5.4 years; education level: 11.2±4.9
Clinical and nocturnal variables
The OSA patients did not differ significantly in comparison to the healthy controls for sociodemographic variables, such as age and educational level. The clinical data and the nocturnal respiratory variables for the OSA patients are reported in Table 1. In each control subject AHI was <5 (AHI: 3.2±1.3).
Cognitive evaluation before CPAP therapy
The mean scores obtained in OSA patients and controls in the Beck Scale, ESS, and neuropsychological tests are reported in Table 2.
The daytime somnolence, evaluated by ESS, was greater in OSA
Discussion
The main aim of this study was to assess the effects of OSA on cognitive function and the potential reversibility of cognitive impairment after short- and long-term treatment with CPAP. Unlike most previous reports, in our study we examined an homogenous sample of OSA patients, in terms of clinical and polysomnographic characteristics. Our results demonstrated that OSA patients showed cognitive impairments in some neuropsychological areas: sustained attention and learning abilities, executive
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