Does cosleeping contribute to lower testosterone levels in fathers? Evidence from the Philippines.
Level 3 - non-randomized controlled study
Prospective longitudinal cohort study with non-randomized comparison groups
PubMed 22957016 · doi:10.1371/journal.pone.0041559
What was done
Data from a longitudinal study in metropolitan Cebu, Philippines, were analyzed across two timepoints (2005 and 2009) in a cohort of 362 men (mean age 26.0 ± 0.3 years in 2009). Participants were classified by sleep proximity to their children: same-surface cosleepers, roomsharers (different surface, same room), or solitary sleepers. Morning and evening (PM) testosterone (T) levels, diurnal T decline, and longitudinal changes in T over 4.5 years among men transitioning to fatherhood were compared across groups.
What was found
A large majority of fathers (92%) practiced same-surface cosleeping. Compared to solitary sleepers, same-surface cosleeping fathers showed significantly lower evening T and a greater waking-to-evening diurnal decline in T (both p < 0.05). In men who were non-fathers in 2005, transitioning to fatherhood with same-surface cosleeping at 2009 follow-up was associated with a significantly greater 4.5-year longitudinal decline in PM T compared to solitary sleeping fathers (p < 0.01). Baseline T in 2005 did not predict subsequent sleeping arrangements in 2009 (p > 0.2). Specific numerical testosterone concentrations and confidence intervals were not reported in the abstract.
Why it matters
This study provides evidence that close physical proximity during sleep is associated with neuroendocrine changes in fathers, specifically greater suppression of evening testosterone during the transition to fatherhood.
Limits
The cohort was heavily skewed toward same-surface cosleeping (92%), leaving a very small comparison group of solitary sleeping fathers. The study is observational and restricted to young men in metropolitan Cebu, Philippines, limiting generalizability to populations where solitary sleeping is standard. Sleep disruption, nighttime awakenings, and daytime childcare hours were not reported in the abstract.
Cited by
- supports In longitudinal research in the Philippines, fathers who spent more time providing hands-on care and co-sleeping with infants showed steeper drops in testosterone.