Chronic high blood pressure can be linked to sleep apnea, researchers at the University of Wisconsin Medical School have found.
Published in the current Archives of Internal Medicine, the study is the first analysis of a large segment of the population to confirm what physicians have often observed: hypertension occurs in many of their patients who experience breathing disturbances during sleep.
Sleep apnea may account, in fact, for hypertension in a substantial number of American adults, suggested study director Terry Young, professor of preventive medicine.
"If we assume that there is a causal relationship between sleep-disordered breathing and hypertension, we can estimate from our data that among working-aged adults, sleep apnea would contribute to high blood pressure in approximately 400,000 women and two million men," she said.
Young noted that breathing pauses associated with sleep apnea are known to trigger regular bursts of elevated blood pressure in people as they sleep. To learn whether the episodes resulted in elevated daytime blood pressure, the UW researchers studied 1,060 employed people aged 30-60 participating in the Wisconsin Sleep Cohort Study.
Scientists have learned much from the ongoing investigation of randomly selected Wisconsin state employees: the prevalence of sleep apnea is much greater than previously expected; smoking puts people at increased risk for sleep apnea; doctors are failing to recognize sleep apnea in women; and sleep apnea is associated with car accidents.
In the current study, researchers found that people with mild to moderate sleep apnea, or those who experience 15 breathing pauses an hour as they sleep, were 1.8 times more likely to have hypertension than those who didn't experience apnea.
The UW researchers also noted a dose-response relationship between sleep apnea and the risk for hypertension. The more severe the apnea, the greater the increment in blood pressure, they found.
"This is a public health concern because the prevalence of even mild to moderate sleep apnea is so high," said Young, noting that nine percent of women and 24 percent of men experience sleep apnea of this severity. "Most of these cases go undiagnosed."