Abstract
BackgroundLight information is the most important cue of circadian rhythm which synchronizes biological rhythm with external environment. Circadian misalignment of biological rhythm and external environment is associated with increased risk of depression, insomnia, obesity, diabetes, cardiovascular disease, and cancer.Increased light transmission by cataract surgery may improve circadian misalignment and related health outcomes. Although some observational studies have shown improvement of depression and insomnia after cataract surgery, randomized controlled trials are lacking. We will conduct a parallel-group, assessor-blinded, simple randomized controlled study comparing a cataract surgery group at three months after surgery with a control group to determine whether cataract surgery improves depressive symptoms, sleep quality, body mass regulation, and glucose and lipid metabolism.Methods/DesignWe will recruit patients who are aged 60 years and over, scheduled to receive their first cataract surgery, and have grade 2 or higher nuclear opacification as defined by the lens opacities classification system III. Exclusion criteria will be patients with major depression, severe corneal opacity, severe glaucoma, vitreous haemorrhage, proliferative diabetic retinopathy, macular oedema, age-related macular degeneration, and patients needing immediate or combined cataract surgery. After baseline participants will be randomized to two groups. Outcomes will be measured at three months after surgery among the intervention group, and three months after baseline among the control group. We will assess depressive symptoms as a primary outcome, using the short version geriatric depression scale (GDS-15). Secondary outcomes will be subjective and actigraph-measured sleep quality, sleepiness, glycated haemoglobin, fasting plasma glucose and triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, body mass index, abdominal circumference, circadian rhythms of physical activity and wrist skin temperature, and urinary melatonin metabolite. Chronotype and visual function will be assessed using the ‘morningness-eveningness’ questionnaire, the Munich chronotype questionnaire, and the National Eye Institute Visual Function Questionnaire.DiscussionAlthough there are potential limitations due to the difference in duration from baseline survey to outcome measurements between two groups, any seasonal effect on the outcome measurement will be balanced as a result of continuous inclusion of participants through the year, and outcomes will be adjusted for day length at outcome measurements at analysis.Trial registrationUMIN000014559, UMIN Clinical Trials Registry, registered on 15 July 2014.
Highlights
Light information is the most important cue of circadian rhythm which synchronizes biological rhythm with external environment
Discussion: there are potential limitations due to the difference in duration from baseline survey to outcome measurements between two groups, any seasonal effect on the outcome measurement will be balanced as a result of continuous inclusion of participants through the year, and outcomes will be adjusted for day length at outcome measurements at analysis
Epidemiological studies among shift workers suggest that circadian misalignment is significantly associated with an increased risk of sleep disturbance [2], depression [3], obesity and metabolic syndrome [4,5], diabetes [6,7], ischaemic heart disease [8,9], and stroke [10]
Summary
To conduct an RCT assessing the long-term effect of cataract surgery is ethically difficult, because the effectiveness of cataract surgery for visual acuity is established. To assess the effect of cataract surgery after three months with minimum disadvantage to the control group due to delayed surgery, we have potential limitations due to the difference of duration from baseline survey to outcome measurements between the two groups. Compared with the control group, the intervention group will spend a longer time from baseline measurement to outcome measurement due to the duration between baseline and surgery, and it may distort the results because of a seasonal effect on outcomes. Trial status At the time of submission, the study protocol has been fixed and registered for clinical trial registration, but the recruitment of participants has not started. NT provided contributions from the engineering aspect for measuring outcomes. All authors contributed to the refinement of study protocol and approved the final manuscript
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