Behavioural responses to COVID19 lockdown will define the long-term impact of psychological stressors on sleep and brain health. Here we tease apart factors that help protect against sleep disturbance. We capitalise on the unique restrictions during COVID19 to understand how time of day of daylight exposure and outside exercise interact with chronotype and sleep quality. 3474 people from the UK (median age 62, range 18 to 91) completed our online 'SleepQuest' Study between 29th April and 13th May 2020 − a set of validated questionnaires probing sleep quality, depression, anxiety and attitudes to sleep alongside bespoke questions on the effect of COVID19 lockdown on sleep, time spent outside and exercising and self-help sleep measures. Significantly more people (n=1252) reported worsened than improved sleep (n=562) during lockdown (p<0.0001). Factors significantly associated with worsened sleep included low mood (p<0.001), anxiety (p<0.001) and suspected, proven or at risk of COVID19 symptoms (all p<0.03). Sleep improvement was related to the increased length of time spent outside (P<0.01). Older people's sleep quality was less affected than younger people by COVID19 lockdown (p<0.001). Better sleep quality was associated with going outside and exercising earlier, rather than later, in the day. However, the benefit of being outside early is driven by improved sleep in 'owl' (p=0.0002) and not 'lark' (p=0.27) chronotype, whereas, the benefit of early exercise (inside or outside) did not depend on chronotype. Defining the interaction between chronotype, mental health and behaviour will be critical for targeted lifestyle adaptations to protect brain health through current and future crises.

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Background COVID‐19 restrictions have been associated with apathy, anxiety and depression in individuals with cognitive impairment 1‐3 and increased stress in caregivers 4 . But despite links between these restrictions and sleep impairment in the general population 5 , effects on sleep in this cohort are not widely reported. Here we determine overall sleep quality in these populations during the first UK lockdown, how this changed over time and explanatory factors associated with longitudinal change. Method Cognitively impaired group (CIG), carer group (CG) and older healthy participants completed online self‐reported validated questionnaires (PSQI, GAD‐7, PHQ‐8 and DBAS) alongside bespoke questions comprising the ‘SleepQuest’ study at two comparable stringent lockdown periods within the UK [t1 – (29/4/20‐13/5/20) and t2 – (5/11/20‐2/12/20)]. Analysis utilised paired t‐tests with Bonferroni correction with 95% confidence intervals. Multivariable linear regression evaluated predictive factors. Result Within the CIG, baseline n = 79 [MCI, n = 33; AD, n = 19; Other, n = 27], mean age 68.7±9.7, with follow‐up data for n = 37. Within the CG, baseline n = 183, mean age 59.4±11.1, follow‐up n = 116. Overall sleep quality by PSQI Total was impaired at baseline (CIG = 7.8±4.3; CG = 7.9±4.0) compared to 6.6±3.6 for older healthy participants (n = 2354). There was a trend towards sleep quality deterioration from t1‐t2 in both groups (CIG ‐ Mean diff = 0.84, CI[‐0.20,1.84], p = 0.111; CG ‐ Mean diff = 0.51, CI[‐0.01,1.02], p = 0.053). PSQI subcomponent analysis revealed increasing sleep medication use in both groups (CIG – Mean diff = 0.83, CI[0.36,1.32], p corr = 0.007; CG – Mean diff = 0.99, CI[0.81,1.17], p corr <0.001). However, levels of daytime dysfunction improved in both groups (CIG – Mean diff = ‐0.54, CI[‐0.87,‐0.21], p corr = 0.014; CG – Mean diff = ‐0.46, CI[‐0.61,‐0.30], p corr <0.001). Within the CIG, affective and behavioural factors at t1 did not predict sleep at t2. Within carers, increased anxiety (total GAD‐7) at t1 predicted worse sleep at t2 (Est[normalised PSQI total] = 0.22, SE = 0.10, p = 0.041). Conclusion Overall sleep quality for individuals with cognitive impairment and their carers was poor at baseline and trended towards further deterioration, although daytime function improved. Within this cohort, potential compensatory strategies included increased use of sleep medication (associated with adverse outcomes). Given impaired sleep may accelerate progression of dementia neuropathology 6,7 , it is important to understand and ameliorate the impact of prolonged socio‐political stressors on people with dementia and their carers.