title: Does cosleeping contribute to lower testosterone levels in fathers? Evidence from the Philippines.
abstract: Because cross-species evidence suggests that high testosterone (T) may interfere with paternal investment, the relationships between men's transition to parenting and changes in their T are of growing interest. Studies of human males suggest that fathers who provide childcare often have lower T than uninvolved fathers, but no studies to date have evaluated how nighttime sleep proximity between fathers and their offspring may affect T. Using data collected in 2005 and 2009 from a sample of men (n = 362; age 26.0 ± 0.3 years in 2009) residing in metropolitan Cebu, Philippines, we evaluated fathers' T based on whether they slept on the same surface as their children (same surface cosleepers), slept on a different surface but in the same room (roomsharers), or slept separately from their children (solitary sleepers). A large majority (92%) of fathers in this sample reported practicing same surface cosleeping. Compared to fathers who slept solitarily, same surface cosleeping fathers had significantly lower evening (PM) T and also showed a greater diurnal decline in T from waking to evening (both p<0.05). Among men who were not fathers at baseline (2005), fathers who were cosleepers at follow-up (2009) experienced a significantly greater longitudinal decline in PM T over the 4.5-year study period (p<0.01) compared to solitary sleeping fathers. Among these same men, baseline T did not predict fathers' sleeping arrangements at follow-up (p>0.2). These results are consistent with previous findings indicating that daytime father-child interaction contributes to lower T among fathers. Our findings specifically suggest that close sleep proximity between fathers and their offspring results in greater longitudinal decreases in T as men transition to fatherhood and lower PM T overall compared to solitary sleeping fathers.
authors.affiliation: Department of Anthropology, University of Notre Dame, Notre Dame, Indiana, United States of America. lgettler@nd.edu
authors.forename: Lee T
authors.initials: LT
authors.lastname: Gettler
authors.forename: James J
authors.initials: JJ
authors.lastname: McKenna
authors.forename: Thomas W
authors.initials: TW
authors.lastname: McDade
authors.forename: Sonny S
authors.initials: SS
authors.lastname: Agustin
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Kuzawa
mesh_terms: D000368:Aged; D017028:Caregivers; D005220:Fathers; D006306:Health Surveys; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D016487:Parenting; D010332:Paternal Behavior; D010679:Philippines; D012424:Rural Population; D012463:Saliva / Q000378:metabolism; D012890:Sleep; D011795:Surveys and Questionnaires; D013739:Testosterone / Q000096:biosynthesis*; D014505:Urban Population
chemical_list: D013739:Testosterone