The goal of this observational study is to evaluate the influence of circadian rhythms on the determination of an individual's immune age. The biomarker IMMAX was calculated for 50 participants aged 20-69 at 8 a.m., 1 p.m. and 6 p.m. on the same day.

Inclusion Criteria:

• aged > 18 years
• knowledge of German or English sufficient to provide verbal explanations and obtain written consent

Exclusion Criteria:

• exercise on the assessment day
• acute infection
• vaccination within the last 4 weeks
• autoimmune disease
• cancer
• drugs that may influence immune cell counts
• participation in other interventional studies during study period

All subjects who are willing to visit the study centre in Dortmund three times a day.