The study, which was undertaken in conjunction with the Royal New Zealand Foundation of the Blind (RNZFB), was recently published in the journal PLosOne. It looked at self-reported sleep habits, sleep disruptions and medication use in people completely blind in one or both eyes; partially-sighted and fully-sighted.
Findings showed a greater rate of self-reported sleeping disorders, and specifically sleep-timing disorders, among blind and partially sighted New Zealanders. Twenty-six percent of people with no light perception in one or both eyes reported drifting sleep patterns (an indicator of an unadjusted biological clock) compared with four percent of fully-sighted respondents.
Principal investigator and chronobiologist Dr Guy Warman says: “It is well known that blind people lacking light perception can have problems keeping their sleep adjusted to a 24-hour day. But until now we haven’t known how big that problem is.”
This can have a major effect on health and wellbeing. “Effectively it can be like jetlag without leaving home,” says Dr Warman.
“In sighted people sleep-timing problems can be treated relatively easily with morning light exposure. For blind people, melatonin taken at the correct dose and at the right time can also be effective.”
In response to questions on sleep treatment approximately half of all respondents in the study reported having taken sleep medication. However, the maximum rate of melatonin use in blind and partially-sighted respondents was only four percent.
“This suggests a therapeutic gap in the treatment of circadian-related sleep disorders in New Zealand which might also be applicable to other countries around the globe,” says Dr Warman.
“The provision of resources by the RNZFB enables many New Zealanders with limited vision to avoid isolation, hold down jobs, and participate fully in our community. Efforts to provide resources to improve their quality of life would be greatly enhanced by addressing the sleep timing problems that are evidently common in this group.”
Dr Warman urges those who are blind or partially-sighted, who think that they might be experiencing drifting sleep, to discuss this with their doctor and to ask whether melatonin may be a useful treatment option.
The study was funded by a grant from the Health Research Council of New Zealand.