The relationship between 6-sulphatoxymelatonin and polysomnographic sleep in good sleeping controls and wake maintenance insomniacs, aged 55-80 years

The pineal hormone, melatonin, is reported to possess hypnotic properties. This has led to an investigation of the relationship between the endogenous melatonin rhythm and sleep. However, this relationship has yet to be fully examined in aged insomniacs and controls. From media advertisements, 16 go od sleeping controls (11F, 5M) and 16 sleep maintenance insomniacs (11F, 5M ), aged over 55 years, were recruited to participate in a study involving f our nights of polysomnographically (PSG) measured sleep followed by a 26 h constant routine. During the constant routine, 2 h urine samples were colle cted and analysed for the melatonin metabolite, 6-sulphatoxymelatonin (aMT. 6S), This was used to determine total melatonin excretion. As well, the fol lowing circadian melatonin parameters were calculated from fifth order poly nomial curve fitting analyses, the goodness of the polynomial curve fit, pe ak melatonin concentration, the phase of the melatonin rhythm, and melatoni n and sleep rhythm synchrony. Apart for one control, all subjects showed si gnificant circadian melatonin rhythms. Although insomniacs showed a greater amount of wakefulness, less sleep in total, and lower sleep efficiency, no significant group differences were observed in any of the melatonin parame ters. In addition, while subjects with more reliable melatonin curve fits s howed shorter sleep latencies and higher sleep efficiencies, correlational analyses revealed no other significant relationships between any melatonin and PSG sleep parameters. Overall, the present results suggest that neither melatonin amplitude nor phase are related to sleep quality in the aged.