Dietary interventions affecting sleep : effects on next day mood, alertness and cognitive function

The primary aim of this thesis was to evaluate the efficacy of dietary/herbal interventions on sleep, and associated daytime consequences that are often the major complaints of poor sleep in the general population. A secondary aim was to develop appropriate methodology for assessment of such interventions in 'the field.' Poor sleepers participated in two placebo-controlled, double-blind, 3-week field studies that included a baseline week, and were assessed after the first night, over two weeks, and at follow up. Outcomes included objective and self-rated measures of sleep, mood, and daytime cognitive performance, which had initially been assessed using caffeine as a model for poor sleep in good sleepers, and a separate sample of poor sleepers. Previously reported beneficial effects for sleep (or stress and anxiety hypothesised to promote healthy sleep) of hops, lemon balm, L- theanine, and a tryptophan rich protein were largely not replicated here. Nor were any clear beneficial effects observed for next day mood and cognitive performance. Although those with insomnia disorder were excluded, insomnia is often undiagnosed and possibly resulted in a sample of poor sleepers with severe sleep complaints. The selection criteria for poor sleepers are of major importance. Furthermore, different mechanisms must be targeted for short- or long-term sleep problems, and sleep needs to be poor enough to show evidence of daytime impairment. Objective daytime outcome measures are not suitable for daily field testing, as multiple nights of improved sleep are necessary to see measurable changes in performance, and these can be influenced by uncontrolled compensatory mechanisms deployed by participants to manage the effects of their poor sleep. For the purpose of assessing changes associated with improved sleep due to interventions in poor sleepers without insomnia disorder, self-rated performance may be a more appropriate and reliable outcome. Feeling refreshed in the morning may be another important primary outcome variable, as this was found to be associated with both sleep quality and daytime performance.EThOS - Electronic Theses Online ServiceGBUnited Kingdo