What is cortisol?
Cortisol is a steroid hormone which is produced by hypothalamic-pituitary axis (HPA axis) which is released in response to stress. Therefore, measuring the cortisol levels is an efficient tool to assess stress levels in humans and animals.
Cortisol varies across a day, following a diurnal curve; it has a sharp rise in the morning, around 30 mins after awakening and then drops suddenly at first; followed by a more gradual decline as the day goes on. Therefore it is very important to measure cortisol levels approximately at the same time of the day to be able to compare cortisol levels.
In this study we are focussing on two types of cortisol levels:
Basal Cortisol level: is a measure of baseline level of individual cortisol which is usually measured over several days at the same time each day –to account for variation within that individual. In order to obtain the baseline level and account for extreme values, we calculate the average cortisol levels measured on a minimum of two samples taken on consecutive days.
Acute Cortisol level: is a measure of the stress response to an event including for example an exciting or stressful situation. Although an increase in cortisol levels is released just a few minutes after exposure to a stressor, it takes an average of 22 mins for this increase to show in the saliva.
Most widely used methods to measure cortisol:
Cortisol can be sampled from blood, urine, faeces or saliva. Saliva is often the most commonly used method of collection as it is easy to use, only requiring people to either take swabs or to provide “drool” samples into tubes.
What can affect cortisol?
Cortisol levels can be affected by many medications, alcohol, nicotine, food (especially acidic food such as fruit), drink and exercise.
What is good practice when measuring cortisol?
Before giving cortisol samples it is good practice to:
• Avoid eating and brush your teeth 30 minutes before the test. This is because foods with high sugar or acidity and tooth paste can affect cortisol levels by making saliva more acidic and increase/decrease bacterial growth.
• Document consumption of alcohol, caffeine, nicotine, and prescription/over-the-counter medications within the prior 12 hours.
• Document vigorous physical activity and the presence of oral diseases or injury.
• If measuring salivary cortisol, ensure no blood contamination is in the sample. This can occur through tooth-loss in children or brushing teeth in adults.
• To rinse mouth with water 2 mins before taking saliva sample.
Cortisol in the LEAD project
Why are we measuring cortisol in the LEAD?
We hope that the interventions used in the LEAD study (the dog intervention and relaxation intervention) may help children to relax. By measuring cortisol levels we may be able to see if this is actually the case.
When are we measuring cortisol?
In the LEAD study we are going to measure basal and acute cortisol levels.
We will measure basal cortisol 3 times on 3 different days before the start and also after the study (again, 3 times on 3 different days). Basal cortisol level will always be measured between 9.30-10am when children should not have had food, brush their teeth or exercise for at least 30 minutes. Basal cortisol measures will give us an average cortisol level for each child before we assess their language and cognitive abilities or do any study interventions.
We will also measure acute cortisol levels immediately before and after some intervention sessions. Acute cortisol level will be measured on three of the intervention days (both before and after intervention sessions). Intervention sessions for each individual child will be held as close to the same time as possible – to control for cortisol variation during the day. With these acute samples we are looking at the effect of a single session spent with the dog/relaxation on children stress levels.
How are we measuring cortisol?
We will measure cortisol from saliva samples, asking the children to spit into a sterile tube.
The tubes of saliva will be carefully labelled with anonymous codes to protect the children’s identities and they will then be sent for cortisol analysis. Once the samples have been analysed they will be destroyed.