A Day In The Life Of Your Body How the "Body Clock" Affects Symptoms of Illness Among the various biologic rhythm cycles that medical chronobiologists study, the 24-hour day/night-activity/rest cycle is considered a key chronobiologic factor in medical diagnosis and treatment. Formally known as the circadian rhythm, it's also referred to as the "body clock." Why is the 24-hour body clock so important? Because so many of our normal body functions follow daily patterns of speeding up and slowing down, intensifying and diminishing, in alignment with circadian rhythm. Interestingly, so do the symptoms of a number of chronic disorders: Allergic rhinitis - (nasal inflammation associated with hay fever) - symptoms of sneezing, runny nose, and stuffy nose are typically worse in the early waking hours than during the day. Asthma - in most patients, symptoms are more than 100 times as likely to occur in the last few hours before awakening than during the day. Stable angina - chest pain and electrocardiographic (ECG) abnormalities are most common during the first 4 to 6 hours after awakening. Prinzmetal's angina - ECG abnormalities are most common during sleep; chest pain can occur even while at rest. Heart attack - most commonly occurs in early waking hours. Stroke - most commonly occurs in early waking hours. Hypertension - highest blood pressure readings typically occur from late morning to middle afternoon; lowest occur during early sleep. Therapy now exists that works with your body clock: Please consult your physician. Clinical studies are underway to further this research. Rheumatoid arthritis - symptoms are most intense upon awakening. Osteoarthritis - symptoms worsen in afternoon and evening. Ulcer disease - pain typically occurs after stomach emptying, following daytime meals, and in the very early morning, disrupting sleep. Epilepsy - seizures often occur only at particular times of the day or night; individual patterns differ among patients. For additional information about Biologic Rhythms, see these MedicineNet.com articles: Biologic Rhythms Body Rhythms and Angina Body Rhythms and Heart Attack Body Rhythms and Hypertension Body Rhythms and Allergies Body Rhythms and Asthma Biologic Rhythms Matching Drug Therapy to the Body Clock Biologic Rhythms and Diagnostic Testing References: The right time? Chronopharmacology - a new science. Nursing RSA Verpleging. 1992;7:23-27. Pharmacology. Smolensky MH, D'Alonzo GE. Medical chronobiology: concepts and applications. Am Rev Respir Dis.1993;147:S2-S 19. Time of day medicine dose is taken may boost its efficacy, cut toxicity. JAMA. 1996;275:1 143-1 144. Medical News & Perspectives.