Summary: Several hormones exhibit functioning degradation of the system over time due to stress, i.e., acute psychological stress will cause gradual degradation in the functioning of the system and leads to variety of diseases. To analyze in a randomized controlled study whether acute psychological stress alters local pro-inflammatory signals in a human model of chronic inflammation, i.e., gingivitis. Chronic inflammation represents a crucial factor in a variety of diseases and factors that contribute to the onset and progression of disease. Psychological stress is assumed to represent such a factor. The acute psychological stressor applied in this study induced a profound cortisod increase, proving its validity as a stressor. Neuropeptides, such as local corticotrophin-releasing hormone (CRH) or substance P (SP), are involved in this process.
Models for reliability estimate using degradation data can be classified into two groups: physics-based (or experimentally based) and statistics-based models. By using the statistics based model for reliability estimate using degradation data we here obtain

(1)

necessary and sufficient conditions for \(R_x (t)\) (i.e., reliability at time ‘\(t\)’ given a threshold degradation level \(x\)) to be a valid reliability function,

(2)

the relationship between the degradation path and the degradation hazard function for the response of stress.