Mild Cognitive Impairment and Obstructive Sleep Apnea

Memory (immediate and delayed recall) will be assessed using HVLT-R. HVLT-R has been used in elders with Alzheimer's Disease and takes 10 minutes to complete. Total score ranges from 0 to 60, a higher score indicates a better memory (better outcome).

The Digit Symbol subtest (DS) from the Wechsler Adult Intelligence Scale (WAIS-R) was used to measure psychomotor/cognitive processing speed. An age-adjusted total scaled score was used for analysis. The adjusted total score ranges from -5.7 to+27. A higher score indicates a better outcome.

Global cognitive function will be assessed using MMSE. It is a 30-item cognitive screen measuring orientation, registration, short-term memory, attention/concentration, language, and constructional capacity. Summary score will be used as a measure of global cognitive function. Total score ranges from 0 to 30, equal to and above 24 is normal (better outcome), less than 21 indicates increasing odds of dementia (worse outcome).

Attention will be measured using SCW. We used the Golden and Freshwater's (2002) version. This version provides paper stimuli for each trial: in the first, columns of the words"red""blue" and "green" are printed in black ink (Word Reading; W); in the second, columns of the same words are printed in red, blue, or green ink (Color Naming; C); in the third, the words "red" "blue" and "green" are printed in a colored ink (red, blue or green) that does not match the word (Color-Word; CW). Participants read each page aloud as quickly as possible for 45 seconds and receive a score for each trial representing the number of items correctly read aloud. The Interference T-score is obtained by first calculating a deviation score by subtracting a predicted CW score from the obtained raw CW score (in 45s). The obtained deviation score is then converted to an Interference T-score. Lower T scores(T<40) in the Interference condition show reductions in inhibitory control.

Attention/reaction time will assessed using the PVT. The participants sat in a closed and quiet examination room, without any auditory or visual disturbance. A 1-minute mock PVT demonstration was done prior to each test. The PVT visual display was held 14-22 inches from the subject's eyes. The participants were asked to either use the index finger or thumb of their dominant hand to respond to the PVT signals. The participants were instructed to maintain the fastest possible reaction times to a simple visual stimulus: a red light emitting diode displaying time in milliseconds in a window of the portable PVT device. We used number of lapses, defined as mean reaction time above 500 milliseconds (errors of omission) as the primary outcome. Lower score indicates better outcomes (Less lapses).

Daytime sleepiness be assessed using ESS. The ESS asks the respondent to rate the likelihood of falling asleep in eight specific situations using a four-point Likert scale ranging from never dozing to high chance of dozing. The scale significantly correlates with the frequency of apneas and is a clinical and research standard for the assessment of daytime sleepiness. The total score ranges from 0 to 24, a higher score indicates higher chance of daytime sleepiness (worse outcome).

Everyday function will be assessed using FOSQ. It is a 30-item Likert-scale, self-report, disease-specific functional status measure written at the 4th grade level. The total score ranges from 0 to 120, a higher score indicates a better outcome.

This informant-rated composes of multiple subscales, to evaluate cognitively based functional abilities in older adults. The factor structure of Everyday Cognition was assessed with confirmatory factor analysis, which supported a 7-factor model including 1 global factor and 6 domain-specific factors (Everyday Memory, Language, Visuospatial Abilities, Planning, Organization, and Divided Attention). The total mean score ranges from 0 to 57. A higher score indicates a worse outcome.

Global change (progression) will be assessed using ADCS-CGIC at 1 year. It has 8 categories as markedly improved, moderately improved, minimally improved, not changed, minimally worse, moderately worse, markedly worse, missing response.

Cognitive ability will be assessed and staged using CDR. It contains 6 items (memory, orientation, judgement and problem solving, community affairs, home and hobbies, personal care), and each item ranges from 0 to 3. The total score ranges from 0 to 18, a higher score indicates a worse outcome. We observed the change of CDR score from baseline to 1-year follow up. Improved on CDR was defined as a lower CDR score compared to baseline. Reference group is unimproved, defined as worsened (higher) CDR or unchanged CDR compared to baseline.