The objective of the present study is to synthesize the existing empirical literature
and perform a meta-analysis of published data on the relationship between cortisol
and telomere length. We systematically searched studies that examined the relationship
between cortisol and telomere length in humans on electronic databases and screened
reference sections of included articles. Fourteen studies were included in the meta-analysis,
with effect sizes being extracted for two cortisol measures: basal cortisol levels
and cortisol reactivity to acute psychological stress. Results from random-effects
models showed that basal cortisol levels (13 effect sizes from 12 cross-sectional
studies, N = 3675 participants) were not significantly correlated with telomere
length ( r = −0.05, 95% CI [−0.11, 0.02]). Further, results stratified by the specimen
type for cortisol measurement (i.e., saliva, urine, blood) showed that none of the
three basal cortisol level measures were correlated with telomere length. However,
we found a statistically significant correlation between salivary cortisol reactivity
to acute psychosocial stress (6 cross-sectional, N = 958 participants) and telomere
length ( r = −0.13, 95% CI [−0.23, −0.03]). Subgroup analyses revealed that correlations
between salivary cortisol reactivity and telomere length were more evident in studies
conducted among children (vs. adults) and in studies that included female participants
only (vs. both gender). However, the small number of available studies limits the
conclusions derived from subgroup analyses, and more studies are needed before moderator
effects can be properly established. Overall, findings of this study support the existence
of a relationship between cortisol reactivity and telomere shortening.