It's based on a science called chronomedicine, which holds that this ebb and flow vastly affects your blood pressure, heart rate -- all manner of bodily processes and disease symptoms -- and can guide doctors to optimal treatment times, Smolensky tells WebMD.
"By paying attention to our body clocks, our body rhythms -- which includes 24-hour rhythms, women's menstrual cycle rhythms, and even annual rhythms -- we can achieve better health, we can understand the rhythm of alertness, we can better prevent and treat illness," Smolensky tells WebMD. "This biological clock controls when we're sleepy, when we're alert, when the symptoms of our diseases are going to be most and least intense. It will affect how we respond to medications in terms of their therapeutic efficiency and their side effects."
When Smolensky began researching the book, he found that scientific journals were full of relevant information. "There was so much information in the literature that people and doctors don't know," he tells WebMD.
Here are a few tidbits Smolensky and co-author Lynne Lambert gleaned from their research:
- Most chronic illnesses in women worsen in the days just before a menstrual period. Also, the best time to schedule a Pap smear is near ovulation, midway between a woman's monthly periods; test results are most accurate then.
- Men produce more and faster-moving sperm in the afternoon, and having lots of speedy sperm boosts the odds of that one will reach the egg in the few days each month when conception is possible. For couples trying to conceive, several studies have shown that sperm counts are highest in spring and lowest in summer, and the late afternoon may be the best time for intercourse.
- Day 14 of a woman's menstrual cycle is a big one: ovulation occurs, conception is most likely, sexual fantasies and desires peak, orgasms are more intense, and the senses of vision and smell are more acute.
- If you're having dental work done, take note: anesthetics last about 32 minutes when given in the afternoon, as compared to only 12 minutes in the morning. Studies of patients undergoing root-canal surgery, tooth extraction, gum surgery, and other painful procedures show similar results.
- Taking aspirin and other non-steroidal anti-inflammatory drugs such as Advil with dinner or before going to bed is more effective in controlling the inflammation and pain of rheumatoid arthritis, a disease marked by inflammation in the joints. That's because the medication is in the tissues overnight and still there in the morning, when swelling is worst. Also, this reduces the potential side effects of these drugs, such as bleeding ulcers.
- The time of day you have diagnostic tests done or undergo medical procedures can alter the results. If you have asthma, for example, your airway function will vary over the day. It probably is best in mid-afternoon, and poorest in the early morning. If you routinely go for a checkup in the afternoon, your doctor may think your treatment is working fine. But if you go first thing in the morning, the severity of your illness will be more apparent.
- Blood pressure is often 20% higher in the late afternoon than in the morning. If you regularly have checkups in the afternoon, this could be telling your physician that your condition is worse than it really is.
- Glaucoma tests should be taken in the morning, when eye pressure is close to its highest.
- Some chemotherapies -- such as 5-fluorouracil, which is used to treat cancers of the intestinal tract -- are best tolerated and cause the fewest side effects when given by infusion while the patient sleeps at night. Other chemotherapies are best tolerated when given in the morning.