This means that caffeine mainly works by occupying adenosine receptors in the brain, specifically, receptors that influence sleep, arousal, and cognition. Once it is in the body, caffeine will persist for several hours, and takes about six hours for one half of the caffeine consumed to be eliminated. When caffeine reaches the brain, it increases the secretion of norepinephrine which is related to the "fight or flight" response. The rise in norepinephrine levels increases activity of neurons in areas of the brain and the symptoms resemble those of a panic attack.The half-life of caffeine is roughly 3–4 hours in healthy adults, however, it is dependent on a variety of variables such as age, liver function, medications, level of enzymes, pregnancy. This short half-life has been found to help out daytime functioning, but increase the side effect of sleep problems. So, while caffeine has the potential to increase performance, it comes at a cost of sleep deprivation which in its own way can counter the main point of caffeine. Sleep deprivation alone can cause a variety of problems associated with cognitive control and functions. This can include reduced alertness, attention, vigilance, speed of motor functions.Though caffeine can be shown to decrease the quality of sleep, there is no evidence that caffeine affects all people the same way. In fact, some people report no sleep problems despite regularly consuming caffeine. Regular intake of caffeine may be normal for a person so it is understandable how they may still get satisfactory sleep.
The ages range from 50 to 80 years with a male predominance and a median age of 67 years. VC may grow large in size, resulting in the destruction of adjacent tissue, such as bone and cartilage. Diagnosis
Surgeons must provide adequate specimens including the full thickness of the tumors and adjacent uninvolved mucosa for correct histopathology diagnosis. Subtypes
Epithelioma cuniculatum (also known as Carcinoma cuniculatum,: 654  and Ackerman tumor) is a subtype of verrucous carcinoma, characterized by well-differentiated epithelial cells which lack cytological atypia, but display a blunt papillary/pebbly surface and keratin-filled crypts extending deep into the connective tissue. These keratin-filled resemble rabbit burrows. It is located almost exclusively on the foot, but at least oral location has also been described. Treatment
Surgery is considered the treatment of choice, but the extent of surgical margin and the adjuvant radiotherapy are still controversial. Surgical excision alone is effective for controlling VC, but elective neck dissection is not necessary even in patients in the advanced stages. Prognosis
Most patients with verrucous carcinoma have a good prognosis. Local recurrence is not uncommon, but metastasis to distant parts of the body is rare. Patients with oral verrucous carcinoma may be at greater risk of a second oral squamous cell carcinoma, for which the prognosis is worse. See also
List of cutaneous conditions
List of verrucous carcinoma subtypes

References
External links
eMedicine.com article