Use of a multivitamin or multiple single vitamins was associated with poorer sleep maintenance compared to individuals who did not take vitamin supplements. There was a tendency for vitamin users to have a greater number of awakenings during the night, more total wake time during the night, greater use of sleep medications, and a higher rate of insomnia than non-users. Controlling for age, gender, and ethnicity partially attenuated the sleep-vitamin association. Future research should examine the influence of these variables more closely to better illuminate differential effects vitamins may have on sleep for different populations.
This study was conducted to stimulate a scientific dialogue on the subject of vitamins and sleep, not to resolve the matter, and many questions remain unanswered. There are at least five plausible interpretations for the observed association between vitamin use and disturbed sleep, and the present study cannot assign differential credence to any one. First, vitamin use causes disturbed sleep in some individuals. Second, no single vitamin causes disturbed sleep, but the interaction of some unknown combination of vitamins does cause disturbed sleep. Third, individuals experiencing disturbed sleep are more likely to initiate vitamin use. Fourth, there is no causal link between vitamins and poor sleep, but factors that motivate insomnia, such as anxiety and depression, also invite vitamin use. Fifth, the results of this study are unreliable and unreplicable.
This is one of the first studies to test the association between vitamins and sleep. These data should be considered preliminary, needing replication, and needing clarification, but are nonetheless provocative and worthy of further investigation. Methodological shortcomings and low response rate restricted our ability to tease out potentially important associations in this data set. For example, we could not evaluate dose effects, time of day administration, or duration of use. Dosing may be of particular importance because either toxic or inadequate amounts of vitamins have been shown to affect sleep adversely. In addition, inadequate distribution of sample size prevented analysis of particular vitamins, such as possible beneficial effects of vitamin E. Like all other cross-sectional studies, uncontrolled variables may have corrupted the age influence. Finally, we did not collect data on herbal supplements so their influence in the present study is indeterminate.
For future consideration, one plausible methodological approach that would illuminate salient factors would be to assign vitamin use, singly and in combinations, to normal sleeping