ACTIVITY AND LIGHT EXPOSURE IN THE OLD ORDER AMISH

Light profoundly influences physiology and behaviour, through a photochemical, melanopsin. Modern lighting is theorized to interfere with the with melanopsin and contribute to Seasonal affective disorder (SAD), characterized by recurring episodes of low mood-energy, excessive sleeping and eating in the fall-winter. Old Order Amish [OAA], a rural population not using any grid-fed lights, following seasonally dictated lifestyle and reported to have low SAD incidence, represents unique opportunity to test the possible mitigating effect of interaction between seasonal variations in total/spectral light and sleep-pattern changes on SAD. Daily/seasonal sleep-pattern and ambulatory light-exposure in forty healthy consenting OAA subjects (age- 25–74, mean53.5, 65%F) were investigated using Actimeter/light logger, on the wrist for a period of three consecutive days months apart. Actiwatch logged total light-exposure [Lux]; blue, green, and red spectral response [μW/cm2] using a photo-diodes; activity, and sleep/ wake periods with an accelerometer. Complete data from thirty-three participants analyzed using METLAB, for daily light-exposure/ sleep-wake profile during periods of pre/post-twilight, 2 hr. Pre/post-sleep, sunrise to sunset, and compared between shorter to longer photoperiod. Daily/seasonal spectral variation of ambulatory light calculated. Effect of the spectral changes on melanopsin photoreception investigated by calculating ‘melanopic-flux’, compared to the photopic exposure. OAA woke up before and slept post twilight, irrespective of photoperiod, suggesting artificial light exposure at all day-lengths, and one-Hr. less sleep in longer photoperiods. High daytime light-exposure (>1500 Lux) irrespective of photoperiod, and very low pre-sunrise and post-sunset exposures, indicate high amplitude light-dark cycle. Seasonal variation in light exposure, quantitatively and spectrally, during critical circadian entrainment periods [2Hr post wake/ pre-sleep], was NOT observed. Pronounced day/night difference in spectral composition, with increase in red spectrum exposure at dawn/dusk and during the 2h preceding sleep indicating low wavelength artificial light sources. Calculated melanopic-flux indicated very low artificial melanopsin activation Results support that certain light-exposure patterns, but not hypothesized seasonal variation in intensity and wavelength, could be contributing to low rates of SAD and high morningness in OOA NIH grant K18MH093940 (PI Postolache).