Skeletal Effects of Chronic Night Shift

Inclusion Criteria * Healthy, nonpregnant adults 20-50 years old who recently (≤6 months) graduated from nursing school and were hired by University of Colorado Hospital for their first nursing position * For women to be eligible, they must be premenopausal, not breastfeeding, not pregnant with no plans to become pregnant during the year of observation and willing/able to maintain their current method of contraception use as detailed below. * Willing and able to travel to/from CU-AMC for study measurements at baseline and quarterly for one full year Exclusion Criteria * Non-nursing school related shift work 1 year prior to study. (note: many nursing students work as an Advanced Care Partner (ACP) or as a Student Nurse Extern (SNE) and these positions will not be considered exclusionary). * Current smokers at baseline (or within the previous year of study). * Individuals who are concurrently participating in another research protocol that would influence their safe participation in this study. For example, participants involved in a study that requires blood draws or ingestion of experimental medication as this would increase the risk of participation in our study and/or compromise study results. * Any clinically significant unstable medical or surgical condition within the last year (treated or untreated), including history of a clinically significant abnormality of the neurological system (including cognitive disorders or significant head injury) or any history of seizure…