Hair is more than just a biological feature. It serves as protection, insulation, and even sensory input for many species. Beyond its everyday role, hair is becoming an increasingly important sample type in research. Hair provides a non-invasive way to measure biomarkers, like cortisol, that reflect stress levels over time.
This makes hair a powerful tool for scientists studying both animals and humans. In fact, using hair to measure cortisol levels offers insights into long-term stress and health conditions. Let’s explore eight key research studies that use hair to measure cortisol across different species, showcasing its value in scientific research.
1. Age and Hair Cortisol Levels as Predictors of SARS-CoV-2 Infection
- Published: 2024
- Species: Human
- Sample: Hair
In this study, researchers measured hair cortisol levels to evaluate chronic stress among healthcare workers during the SARS-CoV-2 pandemic. By comparing cortisol levels from workers who contracted the virus with those who did not, they found higher hair cortisol levels were linked to a higher risk of infection, especially in older individuals. This study highlights the use of hair as a non-invasive way to track long-term stress and its impacts on health.
2. Behaviour and Welfare Assessment in Rabbits: The Role of Housing Systems
- Published: 2024
- Species: Rabbit
- Sample: Hair, Saliva
Researchers studied how different housing environments affect the stress and behavior of rabbits. Hair cortisol levels indicated chronic stress, particularly in group-housed rabbits, despite their increased physical activity. The results demonstrated how hair is a useful tool for assessing both welfare and stress in farm animals.
3. Biobehavioral Predictors of Pain Intensity and Chronic Pain in African-American Adults
- Published: 2024
- Species: Human
- Sample: Hair
The African-American population has been the focus of many studies related to chronic stress and pain in adults. Hair samples were used to track cortisol levels, revealing that chronic pain episodes were linked to higher stress. Analyzing trends in the data, researchers helped predict pain intensity and the likelihood of future pain episodes.
4. Coping Strategies and Their Impact on Hair Cortisol in Marginalized Parents
- Published: 2024
- Species: Human
- Sample: Hair
Another study measured hair cortisol in socioeconomically marginalized parents to understand how stress coping strategies affect long-term stress. The study found that hair cortisol levels were directly influenced by different coping methods, especially emotion-focused strategies. This provides insight into how chronic stress manifests in populations facing constant challenges. Doctors are then able to create better treatment plans for their patients.
5. Keratinase Digestion to Improve Steroid Hormone Extraction from Hair
- Published: 2021
- Species: Echidna, Squirrel, Whale, Bird, Lizard
- Sample: Hair, Spines, Feathers
Stress isn’t only a problem for humans. Researchers investigated ways to improve hormone extraction from keratinous tissues like hair using keratinase. The enzyme boosted hormone yields from hair, feathers, and baleen, making it easier to study stress levels in diverse wildlife. This study showcases how small improvements in assay techniques can provide more accurate results for measuring stress markers like cortisol.
6. Stress Hormones in Sea Lions and Seals: Hair as a Stress Marker
- Published: 2020
- Species: Sea Lion, Seal
- Sample: Hair
This research validated hair as a reliable sample for measuring stress hormones in pinnipeds (commonly known as seals). Hair was shown to store cortisol and other hormones, remaining stable over time. The findings highlight hair’s utility for wildlife endocrinology, especially for monitoring stress without invasive methods. This proved beneficial to researchers unable to get other sample types.
7. Hair Cortisol Levels in Postpartum Dairy Cows: Links to Health and Reproduction
- Published: 2019
- Species: Cattle
On several dairy farms, researchers measured cortisol levels in dairy cows to examine how stress affects reproduction. They found that cows with higher cortisol levels had delayed artificial insemination and other reproductive issues. Hair provided a reliable way to track chronic stress in livestock and its impact on fertility. Dairy farmers were able to make changes to improve productivity.
8. ACTH Administration and Hair Cortisol in Goats
- Published: 2018Â
- Species: GoatÂ
- Sample: HairÂ
This study explored how repeated ACTH administration affected stress and reproductive function in goats. Researchers found no immediate change in hair cortisol levels, but chronic stress still influenced reproductive outcomes. This research underscores hair’s role in reflecting long-term stress, even when short-term cortisol spikes are not detectable.
Splitting Hairs as a Non-Invasive Biomarker Source
Hair is proving to be a vital resource for studying stress and health in both humans and animals. It offers a non-invasive way to measure long-term cortisol levels, providing valuable insights into how stress affects various species.
As these studies demonstrate, hair can tell researchers much about the health, stress levels, and well-being of the animals or humans from which it comes. With Arbor Assays’ wide range of cortisol test kits and assays, scientists can easily measure cortisol and other hormones in hair, supporting their research in stress, health, and wellness across species.