As per the study conducted and research paper published by Dr. Frank B. Hu, Dr. Walter C. Willett, Dr. Alberto Acherio and others in the American Journal of Epidemiology, “Prospective Study of Snoring and Risk of Hypertension in Women”, it was examined whether the association between hypertension and snoring held true. The study conducted in 1986 involved 73,231 US nurses between the ages of 40 and 65 years. None of them had any diagnosed cancer or cardiovascular disease.
Hypertension or high blood pressure is a chronic condition wherein there is long term force of the blood putting high pressure on the artery walls. It leads to a host of health issues including cardiac diseases.
Blood pressure is measured as the amount of resistance to the blood circulation in the arteries and the amount of blood pumped. Hypertension arises when the more blood is pumped by the heart and if the arteries are narrow, the blood pressure goes up. It is measured in mm HG i.e., millimetres of mercury. It is determined as systolic pressure (top reading) and diastolic pressure (bottom number).
The systolic pressure is the pressure of the arteries when the heart beats while the diastolic pressure is the pressure within the arteries between two heartbeats.
After following up with each one for 8 years, 7,622 incidents of medically diagnosed hypertension was reported. Other elements that were directly associated with snoring included waist circumference, BMI, smoking, old age, weight gain, sedentary living, and sleeping on their back.
As per the clinical study that started in 1986, the doctors conducting the research used self-reported blood pressure levels in 1986, 1988, 1990 and 1994 for different models to study the correlation between snoring and hypertension. The researching team used multiple linear regression models to find the difference in blood pressure levels in the various categories of non-snoring and snoring groups based on:
- Smoking status – never, quit smoking, currently smoking of 1-14, 15-24, and over 25 cigarettes per day
- Nurses age
- BMI (body mass index)
- 7 categories of waist circumferences
- Consumption of alcohol (0, 1-4, 5-14, and >15 g/day)
- Physical activity
They conducted both prospective and cross-sectional analysis while analyzing the hypertension diagnosis. For finding the ratio of hypertension, the non-snorers were considered as the reference group.
When the researchers did the prospective analysis of hypertension as a dependent factor, the follow up time was accrued until June 1, 1994 or the date of hypertension diagnosis; diagnosis of cardiac issues such as angina pectoris myocardial infarction, and coronary artery surgery; stroke; and even death. It was based on the individuals in the various categories including non-snoring, occasional snoring, and regular snoring.
Additionally, for the multivariate analysis that used the pooled logistic regression, adjustments were done for the confounding variables such as BMI in 1986, age, status of smoking, use of alcohol, and physical activity undertaken. Later on, living arrangements and marital status were also considered.
Thus, the results showed that 17,511 or 23.9% of women reported hypertension diagnosed by a doctor. In the 8 years of follow-up, there are over 7,622 cases of high blood pressure (hypertension) that was diagnosed. However, 65% of women reported snoring, 26% never snored, and only 9% reported regular snoring.
Hours of sleep
- 5% women slept 5 hours or less
- 25% women slept 6 hours
- 41% women slept 7 hours
- 245 women were able to sleep for 8 hours
- 5% women reported over 9 hours of sleep
In 1972, all the participants of the study were married and in 1980, 84% were still married. As per the statistics revealed, 11% of those who regularly snored were widowed or divorced while 9% were married. Another set of data revealed that in 1992, 74% of the women were either married or had a partner. Out of that group, 10% who snored were single and 9% were married or had partners.
Other Factors Contributing to Snoring
As seen in the study, older women tend to snore more but the regular snoring did not increase after they turned 60 years. People that smoked in the past or even those who had given up snoring for the past 10 years had higher prevalence of snoring than non-smokers. Those that were current smokers had a higher risk of snoring as the number of cigarettes they smoked increased.
Body Mass Index (BMI)
In 1986, the BMI was strongly linked with regular snoring. Women with a BMI > 30 kg/m2 were more likely to snore 11 times more than those with normal BMI with less than 21kg/m2.
It was seen that those women that had higher BMI in 1976 but lost weight in the ensuing 10-year period had lower prevalence of snoring than those that kept a stable weight while those that gained weight over the years had an increased chance of regular snoring. When the researchers put the BMI for 1976 and 1986 into the model, the association was crucial in showing that obesity enhances snoring.
As per the study’s multivariate analysis, it was observed that physical activity lowered the risk of snoring. Active women snored less while those who consumed alcohol over 15 g/day showed higher snoring levels than women that did not drink.
Additionally, in 1986, the average reported blood pressure differences (systolic/diastolic) between non-snorers and snores after adjustments were made for BMI, age, smoking alcohol consumption and physical activity. For the level of hypertension that was reported in 1986, 1988, 1990, and 1994, there was an increase in regular snorers and occasional snorers as compared to non-snorers. It was observed that the variation in the systolic pressure of non-snorers and snorers was 2.0mmHh while in the diastolic pressure was around 1.2 mmHg.
Connection between Hypertension and Snoring
In the large group of women that were observed for years, it was seen that regular snoring was connected to a higher risk for hypertension in prospective analysis and cross-sectional study. The diastolic and systolic pressure levels were higher in regular snorers and extremely low among non-snorers.
In the case of occasional snorers, the levels were intermediate. The researchers corroborated various predictors of snoring in other groups such as age, obesity and smoking. It was noticed that body fat distribution, waist-hip ratio, physical activity and sleeping positions contributed to snoring in many cases. Weight gain led to more cases of snoring while losing weight led to a lower occurrence of snoring.
The Wisconsin Sleep Cohort (K.M. Hia, T.B Young, T. Bidwell, et al – Sleep Apnea and Hyper-tension. Ann Intern Med 1994; 120:382-8) reported that after considering age, BMI, and gender, there was a strong correlation between hypertension and sleep apnea.
In the current study, it was observed that there was small, yet enhanced risk of hypertension among occasional and regular snorers. The researchers speculated that snoring with sleep apnea can increase the risk of cardiovascular disease by the repetitive arousal of the sympathetic nervous system.
With 97% of the women getting their blood pressure checked during 1986 to 1988, detection bias can be overruled when considering the positive connection between cases of hypertension and snoring.
In another study – “Snoring as A Risk Factor for Ischemic Heart Disease and Stroke in Men” by M. Koskenvuo, J. Kaprio, and T. Telakivi (BMJ 1987), it proved that snoring was associated with a higher risk of stroke and ischemic heart disease. The intermittent step was developing hypertension. As hypertension does not show any specific symptoms, the detection or diagnosis depends on behavioral factors that may be related to snoring.