The aim of the study is to determine whether a night-time tea can improve subjective sleep quality in healthy sleepers and self-reported poor sleepers, compared to a control drink.

The study will adopt a randomised, double-blind, placebo controlled, crossover design. Sixty-eight healthy adults aged 18+ (34 good sleepers and 34 poor sleepers) will be recruited from the general population. Good sleepers will be recruited if they have a stable sleep-wake schedule (i.e. bed/wake time within the range of 22.00 - 09.00 and with at least 6.5 hours of sleep duration reported per night). Poor sleepers will be recruited if they report subjective sleep difficulties (i.e. poor sleep quality or unrefreshing sleep) and if they display a Pittsburgh Sleep Quality Index total score of >5. Participants will consume both an active tea, and a control tea in a counterbalanced order for 7 days (separated by a 7-day washout period). Participants will complete questionnaires assessing mood, quality of life and sleep and provide blood samples to assess immunological markers. Sleep monitoring will also be conducted using actigraphy sleep monitoring and sleep diaries. Assessments will be made at baseline and following 7 days supplementation.

Inclusion Criteria:

Healthy male and female adults aged 18 years and above. Both good sleepers and poor sleepers will be recruited. Good sleepers will be recruited if they have a stable sleep-wake schedule (i.e. bed/wake time within the range of 22.00 - 09.00 and with at least 6.5 hours of sleep duration reported per night).

Poor sleepers will be recruited if they report subjective sleep difficulties (i.e. poor sleep quality or unrefreshing sleep) and if they display a Pittsburgh Sleep Quality Index total score of >5.

Exclusion Criteria:

Both good and poor sleeper participants cannot participate if they display evidence of current or previous sleep disorders (e.g. sleep apnoea, insomnia, circadian rhythm disorders); an initial screening for sleep disorders will be conducted using the Sleep Disorders Screening Checklist - 25 (SDS-CL).

• Participants must not be shift workers
• Cannot currently be participating in other research trials which will compromise the results here
• Participants cannot take part if they will be sleeping at a location other than their usual residence during participation
• Nor if they have experienced travel across multiple time zones within the last three months or will be experiencing travel across multiple time zones during the study
• Participants cannot take part if they have current or previous mood disturbances
• Are currently unwell with anything that impacts sleep
• Are currently using medication which affects the central nervous system
• Or are currently misusing alcohol or drugs