Attenuated melanopsin-mediated post-illumination pupillary response is associated with reduced actigraphic amplitude and mesor in older adults

Abstract

Study Objectives: This study aimed to explore the relationship between post-illumination pupillary response (PIPR) with sleep and circadian measures in a community sample of healthy older adults. Methods: Eligible participants were invited to complete a 1 week sleep diary and actigraphy, and provide an overnight urine sample to measure urinary 6-sulfatoxymelatonin (aMT6s). PIPR was defined as the (1) pupil constriction at 6 second poststimulus (PIPR-6s) and (2) for -30s beginning 10 seconds after stimulus (PIPR-30s), normalized as a percentage to the baseline pupil diameter, after 1 second of blue and 1 second of red light stimulus, respectively. The Net-PIPRs were reported by subtracting the PIPR to red stimulus from the PIPR to blue stimulus. The relationship between PIPR metrics to aMT6s and actigraphic rest-activity rhythm parameters was examined by generalized linear models. Results: A total of 48 participants were recruited (mean age: 62.6 ± 7.1 years, male: 44%). Both Net PIPR-6s and Net PIPR-30s were significantly associated with actigraphic rest-activity amplitude (B = 0.03, p = .001 and B = 0.03, p = .01, respectively) and actigraphic rest-activity mesor (B = 0.02, p = .001 and B = 0.03, p = .004, respectively). Additionally, the Net PIPR-30s were positively associated with overnight aMT6s level (B = 0.04, p = .03) and negatively associated with actigraphic rest-activity acrophase (B = −0.01, p = .004) in the fully adjusted models. Conclusions: Attenuated PIPR is associated with a reduced actigraphic amplitude and mesor. The reduced retinal light responsivity may be a potential pathway contributing to impaired photic input to the circadian clock and resulted in age-related circadian changes in older adults.