Light therapy improves sleep among older adults with type 2 diabetes and insomnia Original paper

    In this randomized controlled trial, morning light exposure therapy improved sleep quality among older adults with type 2 diabetes and insomnia but did not improve glycemic control in comparison with the control condition.

    This Study Summary was published on April 16, 2024.

    Quick Summary

    In this randomized controlled trial, morning light exposure therapy improved sleep quality among older adults with type 2 diabetes and insomnia but did not improve glycemic control in comparison with the control condition.

    What was studied?

    The effects of light therapy on sleep quality, circadian rhythm, and glycemic control among adults with type 2 diabetes and insomnia in long-term care facilities.

    Subjective sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), and sleep monitoring bracelets were used to assess objective sleep outcomes. The Morningness-Eveningness Questionnaire (MEQ) was used to assess circadian rhythm. The MEQ includes 19 questions and classifies individuals by chronotype, such as “absolute night type”, “intermediate type”, “intermediate morning type”, and “absolute morning type”. The morning types are characterized by earlier sleep and wake times.

    Morning blood samples were collected to assess glycosylated serum protein (GSP) as a measure of glycemic control.

    Who was studied?

    45 Chinese adults (average age of 85; 19 women and 16 men) with type 2 diabetes and insomnia.

    Individuals with visual disorders or blindness were excluded, as were those with other types of sleep disorders besides insomnia, such as narcolepsy.

    How was it studied?

    This 9-week randomized controlled trial included a 1-week baseline assessment, a 4-week intervention period, and a 4-week follow-up period. During the intervention period, all of the participants received light-emitting glasses, to be worn for 1 hour each morning.

    The light therapy group’s glasses emitted blue-enriched white light (blue light wavelength of 468 nm). The glasses produced a brightness of 1,500 lux, which may be comparable to the light exposure from conventional light boxes of 10,000 lux.

    The control group received glasses which emitted fainter yellow light, which did not alter circadian rhythms in previous research.

    What were the results?

    Light therapy reduced (improved) PSQI scores after 4 weeks and at the follow-up assessment compared to the control condition. MEQ scores also differed between groups, with a shift towards eveningness in the light therapy group (average scores went from “intermediate morning type” to “intermediate type”).

    The primary analysis of objective sleep outcomes did not find significant differences between groups, but a post hoc analysis found that objective sleep scores were higher (better) in the light therapy group after the intervention.

    Glycemic control did not improve in either group.

    This Study Summary was published on April 16, 2024.