Most research on hypothalamic-pituitary-adrenal
axis function under aversive conditions has focused on
relatively increased acute episodic, or chronic secretions as an
operationalization of “stress.” Severe or recurrent stress,
perhaps in interaction with individual characteristics, results in
chronically decreased HPA function among some persons
suffering from posttraumatic stress disorder. Little evidence
exists to assess the population distribution of chronic low
cortisol in different free-ranging human populations, as a
manifestation of past trauma or stress. This study reports
findings of chronically depressed ambulatory salivary cortisol
among rural-dwelling Batswana men (n30) compared with
men living in Gaborone (n34), the capital of Botswana,
based on repeated ambulatory sampling. Out of 914 saliva
samples analyzed by radioimmunoassay, 268 (29.3%) samples
(41 urban, 227 rural) were below the minimum detectable dose
(MDD of 0.034 ug/dL) of the assay. Low values were
distributed across comparable times of day as were MDD
samples. There was significant clustering of low cortisol within
individuals; percentage of intra-individual repeats that were
MDD ranged from zero to 94.1% for rural participants
(median59.8%; mean54.8%; SD27.8%), and from zero
to 40% for urban (median0%; mean8%; SD11.9%).
There was no association between number of repeats and
proportion MDD (P[F0.47]0.639; b 10.0045
0.0019). Examination of laboratory quality control suggests
that this pattern is not a result of measurement error, or poor
sample preservation, but instead reflects a difference from
residing in a remote rural versus a central urban community.