Light to improve sleep, cognition, mood and day time alertness

This randomised controlled trial (RCT) is a device based clinical trial, in which the device is the lighting technology installed in the ceiling of the laboratory suite. The computer software which controls the lighting technology is programmed to predetermined settings to deliver 2 different lighting conditions: - Light therapy (LT): white light (illuminance at 500 lux) with enriched blue and green wavelengths (440-560nm) from wake-up time until 3 hours prior to habitual sleep time, at which point the blue wavelengths are attenuated to yield yellow-enriched light (570-750nm) and the lights are dimmed to 90 lux. - Control light: white light (500 lux) from wake-up time to 3 hours prior to habitual sleep time, at which point the lights will be dimmed to 90 lux. All participants on this study must be 50 years or older and have self-reported poor sleep based on the Pittsburgh Sleep Questionnaire (PSQI, global score >5). Eligible participants will reside for four consecutive days on two separate occasions, at the Woolcock Institute in one of our research laboratory suites. On each occasion, participants will be exposed to either LT (intervention condition) or sham LT (control condition) in a randomised order (randomised crossover trial) with an intervening 2-week washout period at home. Sleep will be studied using high density electroencephalography (hdEEG) and electromyography (EMG) on the third night during each light condition. Source localisation will be performed with The Geoscan which is a non-invasive, hand-held, camera tracking device that identifies and digitizes the 256 high-density EEG sensor locations and creates a 3D coordinate file to be used for Source Estimation. The 3D coordinate file of EEG sensor locations is used to create head models to define the path of electrical current from the cortex to the scalp. HdEEG is a new neurobiological measurement tool permitting detailed topographical analysis of brain activity including identifying local sleep intrusions during wakefulness. It allows for neurocognitive phenotyping, identifying new risk markers and evaluating treatment interventions. Melatonin onset will be assessed from saliva samples collected on the third evening prior to sleep. Daytime function will be assessed using standardised computerised neurocognitive tests on the last two days of the laboratory visits. In addition, brain activity will be measured using routine EEG twice during the study in each (intervention or control) condition, while performing cognitive tasks. Overall, the study will allow us to ascertain whether manipulating the spectrum and timing of light exposure can optimise nocturnal sleep, daytime alertness and improve overall quality of life. The following questionnaires will be used to assess the participants eligibility for the study as well as determine their baseline level of sleepiness, quality of life and sleep disorders: - Sociodemographic questionnaire: ethnicity and level of education selection, and lifestyle questionnaire. - Medical History and Medications: medical history and concomitant medication information will be collected by the study coordinator and sleep physician. - Wechsler Test of Adult Reading (WTAR): a neuropsychological assessment tool that estimates an individual's level of intellectual functioning before the onset of injury or illness. Requires verbal pronunciation of a specific set of words. - The Epworth Sleepiness Scale (ESS): rating of general sleepiness in the last two weeks. - Karolinska Sleepiness Scale (KSS): assessment of subjects’ sleepiness over the last 5 minutes. - Insomnia Severity Index (ISI): rating of insomnia-related sleep problems. - Pittsburgh Sleep Quality Index (PSQI): assessment rating sleep quality over the past month. - Horne & Ostberg Morningness-Eveningness Questionnaire: assessment of what time of the day participants are most productive. - The Multivariate Apnoea Prediction Index (MAPI) Questionnaire: assessment for the presence and frequency of apnoea symptoms over the last month. - The Short Form (36) Health Survey: a patient-reported survey of patient health. The following extensive neurocognitive tests will be used to assess improvement in cognition and alertness with the intervention: - Psychomotor Vigilance Task (PVT): a tool which is used to assess sustained attention via a simple reaction time task. Subjects will be asked to press a button as quickly as possible in response to numbers appearing across the stimulus window on a small box. - N-Back (2-back): a visuospatial test that assesses working memory, encompassing short term memory storage and information processing. During this test, subjects will watch letters appear in different locations on the screen and subjects will try to match those in the same location. - The Stroop Task: This computerised test requires subjects to respond to a series of words that are displayed in colours (e.g. the word ‘red’ is displayed in blue) and identify the colour of the word or the definition of the word. - Letter Cancellation Task: This 10-minute test evaluates concentration, attention and visuospatial scanning ability or neglect. Subjects are shown an array of letters and are required to select a specific type of letters from those shown. - Declarative Memory (Word Pair) Task: a computerised memory test where subjects are required to learn a set of word pairs and recall them at different stages following the learning stage. - Procedural Memory (Finger Tapping) Task: assessment of the participants ability to memorise procedures. This Motor Sequence Task requires subjects to repeatedly type a 5-element number on a standard computer keyboard with the subjects’ non-dominant hand. The specific number sequence, which must be typed, is always displayed in front of subjects on the computer screen. - Symbol digit modality test: a cognitive function tests that asks participants to pair specific numbers with given geometric figures.