September 24, 2012

September 24, 2012 (Washington, DC) — Poor sleep quality is associated with a doubling in the risk of resistant hypertension in women, with the mechanism possibly mediated by depression, a new study shows [1].

The study was presented here at last week's American Heart Association High Blood Pressure Research 2012 Scientific Sessions by Dr Rosa Maria Bruno (University of Pisa, Italy).

"I would say that treating insomnia may improve resistant hypertension, although we need further data before we make firm clinical recommendations on this," Bruno told heartwire .

She commented: "There is lots of evidence that sleep disorders are related to cardiovascular events, but most relate to sleep-disordered breathing such as sleep apnea. Also, there have been many studies showing an association between short sleep duration and the incidence of cardiovascular events or hypertension. But we looked at whether insomnia was linked to the severity of hypertension, and we found poor sleep quality was significantly more prevalent in patients with resistant hypertension."

Quality Rather Than Quantity

The researchers reported that it was the quality of sleep rather than the duration of sleep that seemed to be the important factor in the relationship with resistant hypertension. They also found a large difference between men and women.

Bruno noted: "In women, poor sleep quality was strongly related to anxiety and depression and resistant hypertension, but this was not the case for men. This difference remained after accounting for other confounding factors. In women, we found that poor sleep quality was associated with a fivefold increase in the probability of having resistant hypertension, even after adjustment."

She cautioned that as this was only a cross-sectional study, they can conclude there is an independent association between poor sleep quality and resistant hypertension, but they cannot deduce that this is a causal effect. "This needs to be confirmed in a prospective study. It could also be that the hypertension is causing the insomnia, but we believe that the insomnia is making the hypertension worse."

Experimental evidence supports this view. It is known that interrupted sleep stimulates the sympathetic nervous system and increases cortisol levels, both of which cause an increase in blood pressure.

For the study, data on sleep quality, anxiety/depression, and cardiovascular risk factors were collected for 270 patients from a hypertension outpatient unit. Sleep quality was measured by the Pittsburgh Sleep Quality Index (PSQI), and anxiety and depression with the Beck Depression Inventory (BDI). Poor sleep quality was defined as PSQI >5, mild to severe depressive symptoms as BDI score >10. Patients with obstructive sleep apnea were excluded. Resistant hypertension was defined as a failure to control hypertension with three or more drugs.

Complete data were available for 234 patients, half of whom were women. Mean sleep duration was 6.4 hours, and 49% of participants had short sleep duration (less than six hours), which was similar in both sexes.

However, women had higher PSQI scores and a higher prevalence of poor sleep quality. Women showed also higher depression scores and prevalence of depressive symptoms than men.

Sleep and Depression Scores in Women vs Men

Score Women Men p
PSQI score 5.2 3.6 0.03
Poor sleep quality (%) 46 30 0.01
Depression score 4.5 1.8 0.006
Prevalence of depressive symptoms (%) 20 7 0.003

Resistant hypertension was present in 15% of patients, and these individuals had higher PSQI scores than those without resistant hypertension, a difference shown in women but not in men. The association between depression score and resistant hypertension showed a similar trend.

Sleep Scores (PSQI) Related to Resistant Hypertension

Group Resistant hypertension No resistant hypertension p
Entire population 5.8 4.1 0.03
Women 6.8 4.8 0.04
Men 4.7 3.5 0.37


Depression Scores (BDI) Related to Resistant Hypertension

Group Resistant hypertension No resistant hypertension p
Entire population 3.6 2.8 0.02
Women 5.1 3.7 0.03
Men 2.0 1.9 0.53

In a multiple logistic regression analysis (including age, sex, obesity, diabetes, previous CV events, sleep duration, use of hypnotic drugs) poor sleep quality was independently associated with resistant hypertension (OR 2.2). But this relationship lost significance when depressive symptoms were included in the model.