Measurement of the cortisol awakening response (CAR)

Using a combination of wrist-worn activity meters to determine time of awakening and MEMS monitoring of saliva sapling times we are investigating the impact of imprecise saliva sampling on measurement of the CAR.

We have found that delays between awakening and collection of the first sample of between 5-15 minutes results in erroneous overestimation of the CAR as well as earlier timing of the peak. This has led us to explore the CAR at five-minute intervals post awakening which revealed a lag of about 10 minutes from the point of awakening until initiation of the cortisol rise.

We are currently exploring the prevalence of non-CAR events across individuals and days.