Scalp hair samples were collected from ~59,000 adult Lifelines participants during 2A Visit 2. The main aim of hair collection was to use the samples for the assessment of hormone levels, e.g. cortisol (section: physical state).
The hair collection protocol was piloted in a subcohort of 300 participants in september 2013 (during 1A Visit 2) as an additional assessment initiated by researchers at the Department of Internal Medicine of Erasmus University, the Netherlands. During 2A visit 2 it was extended to ~59.000 participants. ~6000 samples have been analyzed for cortisol and cortisone and this data can be requested by sending an e-mail to data@lifelines.nl.

Cortisol levels are typically assessed in serum, saliva, or urine samples. However, due to the circadian rhythm of cortisol, its pulsatile secretion, and the daily variation due to changing circumstances like acute stress, these samples provide non-representative snapshots of chronic cortisol levels in the human body. For that reason, a novel non-invasive parameter to measure cortisol using scalp hair was developed¹⁾, providing the unique opportunity to measure long-term cortisol levels that reflect the mean levels of several months (since hair grows with an average of 1 cm per month). Using this technique, it is now possible to study chronic cortisol levels over time in very large cohorts²⁾.

During 2A visit 2, participants were asked to provide a lock of hair. Nurse practitioners that assisted in the visit cut off a lock of hair close to the scalp using clean scissors. The lock of hair was placed in an envelope, clearly marked and registered, and stored at room temperature.
Participants also filled in a questionnaire about their hair, see the list of questions below.

• Wester et al. (2017) Hair analysis reveals subtle HPA axis suppression associated with use of local corticosteroids: The Lifelines cohort study. Psychoneuroendocrinology 80: 1-6
• van Manen et al. (2019) Scalp hair cortisol and testosterone levels in patients with sarcoidosis. Plos ONE 14(6): e0215763
• Savas et al. (2019) Hair glucocorticoids as biomarker for endogenous Cushing's syndrome: validation in two independent cohorts. Neuroendocrinology 109(2):171-178
• Shukur et al. (2020) Hair cortisol-a method to detect chronic cortisol levels in patients with Prader-Willi syndrome. BMC Endocr Disord; 20(1):166
• van der Valk et al. (2024) Long-term glucocorticoid exposure and incident cardiovascular diseases - the Lifelines cohort. J Clin Endocrinol Metab: dgae081.