Salivary cortisol protocol adherence and reliability by socio-demographic features: the Multi-Ethnic Study of Atherosclerosis.
Collection of salivary cortisol has become increasingly popular in large population-based studies. However, the impact of protocol compliance on day-to-day reliabilities of measures, and the extent to which reliabilities differ systematically according to socio-demographic characteristics, has not been well characterized in large-scale population-based studies to date. Using data on 935 men and women from the Multi-Ethnic Study of Atherosclerosis, we investigated whether sampling protocol compliance differs systematically according to socio-demographic factors and whether compliance was associated with cortisol estimates, as well as whether associations of cortisol with both compliance and socio-demographic characteristics were robust to adjustments for one another. We further assessed the day-to-day reliability for cortisol features and the extent to which reliabilities vary according to socio-demographic factors and sampling protocol compliance. Overall, we found higher compliance among persons with higher levels of income and education. Lower compliance was significantly associated with a less pronounced cortisol awakening response (CAR) but was not associated with any other cortisol features, and adjustment for compliance did not affect associations of socio-demographic characteristics with cortisol. Reliability was higher for area under the curve (AUC) and wake up values than for other features, but generally did not vary according to socio-demographic characteristics, with few exceptions. Our findings regarding intra-class correlation coefficients (ICCs) support prior research indicating that multiple day collection is preferable to single day collection, particularly for CAR and slopes, more so than wakeup and AUC. There were few differences in reliability by socio-demographic characteristics. Thus, it is unlikely that group-specific sampling protocols are warranted.
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA; Department of Epidemiology, Johns Hopkins University Bloomberg School Public Health, Baltimore, MD 21287, USA. Electronic address: sahill@jhmi.edu.
Sherita
S
Hill Golden
Department of Biostatistics, University of Michigan - Ann Arbor, MI 48109, USA.
Brisa N
BN
Sánchez
Center for Social Epidemiology and Population Health, Department of Epidemiology, University of Michigan - Ann Arbor, MI 48109, USA.
Amy S
AS
Desantis
Department of Biostatistics, University of Michigan - Ann Arbor, MI 48109, USA.
Meihua
M
Wu
Department of Epidemiology, Columbia University, New York, NY 10032, USA; Department of Medicine, Columbia University, New York, NY 10032, USA.
Cecilia
C
Castro
Department of Epidemiology, University of California - Los Angeles, CA 10945, USA; Department of Medicine, University of California - Los Angeles, CA 10945, USA.
Teresa E
TE
Seeman
Department of Epidemiology, University of California - Los Angeles, CA 10945, USA; Department of Medicine, University of California - Los Angeles, CA 10945, USA.
Sameh
S
Tadros
Department of Biostatistics, University of Washington, Seattle, WA 98115, USA.
Sandi
S
Shrager
Center for Social Epidemiology and Population Health, Department of Epidemiology, University of Michigan - Ann Arbor, MI 48109, USA.
Ana V
AV
Diez Roux
D000368:Aged; D000369:Aged, 80 and over; D050197:Atherosclerosis / Q000453:epidemiology* / Q000378:metabolism*; D002318:Cardiovascular Diseases / Q000453:epidemiology; D015331:Cohort Studies; D005006:Ethnicity; D005260:Female; D019983:Guideline Adherence; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry*; D012959:Socioeconomic Factors; D013048:Specimen Handling; D014481:United States / Q000453:epidemiology
D006854:Hydrocortisone
Compliance; Cortisol awakening response (CAR); Diurnal cortisol; Population-based study; Reliability; Salivary cortisol