Friday, November 14, 2008

Lack of Sleep Linked to Heart Risk

So people who are unwell tend to have disturbed sleep? Sounds reasonable. But that is not the inference drawn below

Sleeping less than seven and a half hours per day may be associated with future risk of heart disease, according to a report in the November 10 issue of Archives of Internal Medicine, one of the JAMA/Archives journals. In addition, a combination of little sleep and overnight elevated blood pressure appears to be associated with an increased risk of the disease.

"Reflecting changing lifestyles, people are sleeping less in modern societies," according to background information in the article. Getting adequate sleep is essential to preventing health conditions such as obesity and diabetes as well as several risk factors for cardiovascular disease including sleep-disordered breathing and night-time hypertension (high blood pressure).

Kazuo Eguchi, M.D., Ph.D., at Jichi Medical University, Tochigi, Japan, and colleagues monitored the sleep of 1,255 individuals with hypertension (average age 70.4) and followed them for an average of 50 months. Researchers noted patients' sleep duration, daytime and nighttime blood pressure and cardiovascular disease events such as stroke, heart attack and sudden cardiac death.

During follow-up, 99 cardiovascular disease events occurred. Sleep duration of less than 7.5 hours was associated with incident cardiovascular disease. "The incidence of cardiovascular disease was 2.4 per 100 person-years in subjects with less than 7.5 hours of sleep and 1.8 per 100 person-years in subjects with longer sleep duration," the authors write.

Patients with shorter sleep duration plus an overnight increase in blood pressure had a higher incidence of heart disease than those with normal sleep duration plus no overnight increase in blood pressure, but the occurrence of cardiovascular disease in those with a longer sleep duration vs. those with a shorter sleep duration was similar in those who did not experience an overnight elevation in blood pressure.

"In conclusion, shorter duration of sleep is a predictor of incident cardiovascular disease in elderly individuals with hypertension," particularly when it occurs with elevated nighttime blood pressure, the authors note. "Physicians should inquire about sleep duration in the risk assessment of patients with hypertension."


Early exposure to peanuts may prevent allergy

Note that most epidemiological reports make a great thing over the incidence of something being, say, 30% higher. In this case, the incidence is 1,000% higher. Time to think we are onto something real, I would say

Contrary to widespread recommendations, the consumption of peanuts in infancy is associated with a low prevalence of peanut allergy, the results of a new study suggest. "Our study findings raise the question of whether early introduction rather than avoidance of peanut in infancy is the better strategy for the prevention of peanut allergy," write researchers in the Journal of Allergy and Clinical Immunology.

In the UK, Australia and, until recently, the United States, guidelines have recommended that women avoid peanuts during pregnancy and breastfeeding, and should not introduce peanuts into their children's diets during infancy, note Dr. George Du Toit of King's College London and colleagues.

The researchers analyzed the prevalence of peanut allergy and diet histories for 5,171 Jewish children from the UK and 5,615 Jewish children from Israel. They found that children from the UK had a prevalence of peanut allergy that was 10-fold higher than that of children from Israel - 1.85 percent versus 0.17 percent.

"This difference is not accounted for by differences in atopy," the investigators write. Atopy is the inherited tendency to develop common allergic diseases such as eczema, hay fever or asthma.

They also found no differences between the two groups in environmental exposure to common causes of allergy, such as house dust mite and grass pollen, social class or genetic background.

"The most obvious difference in the diet of infants in both populations occurs in the introduction of peanut," they note. Approximately 69 percent of infants in Israel consume peanuts by 9 months of age, compared with just 10 percent of those in the UK.


Comment from the Volokhs:

What the article describing the study doesn't say is that most Israeli infants are introduced to a peanut snack called "Bamba" as one of their first foods. We started giving Natalie Bamba at around eight months, contrary to our doctors' recommendations. My wife said at the time, "I don't care what the doctors here say. Where is the evidence that peanut allergies are caused by early exposure to peanuts? [There is none, just a theory.] We all ate Bamba as babies in Israel growing up, and I never even heard of peanut allergies until I moved to the U.S."

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