A study was undertaken at the University of Helsinki in 1981, under the expert guidance of Dr. Markku Koskenvuo, Dr. Jaako Kaprio, Dr. Tiima Telakivi and their team. It was done to see the correlation between snoring and ischemic heart disease in men.
What Is Ischemic Heart Disease?
Ischemic heart disease or coronary heart disease is a cardiac issue that happens when the arteries in the heart start narrowing, leading to low oxygen and poor circulation of blood in the heart. It leads to a heart attack, if not properly diagnosed and treated.
The study undertaken looked for an association of snoring leading to stroke and coronary heart disease or ischemic heart disease. The study that continued for 3 years follow-up, included 4,388 men that were aged between 40 to 69 years. In a questionnaire that was sent to each, they were asked if they snored regularly, occasionally, frequently or never snored.
Additionally, the hospital records and death certificates were analyzed for the next 3 years to check and see how many developed heart diseases or had a stroke. It was seen that 149 men developed coronary issues while 42 men passed away in the ensuing period. Only men were studied as they have a higher risk of developing ischemic cardia diseases and tend to snore more than women.
Categories Of Snorers
For the sake of analysis, there were three groups of snorers- 1294 habitual and frequent snorers, 480 non-snorers and 2614 occasional snorers. As per the age-related risk of ischemic heart disease in non-snorers and habitual snorers was 1 per 91.
In 1981, the follow up sessions showed that 462 men reported that they had myocardial infarction. The risk of developing ischemic heart disease was higher (1-30) in those that frequently snored, than those that didn’t.
In the journal paper “Cardiac arrhythmias in sleep apnea” by Dr. AG Tilkian and Dr. C. Guilleminault, it was mentioned that heavy snoring which is a constant factor in sleep apnea, is associated with developing arterial hypertension.
Another journal study “Sleep apnea syndromes” by Dr. J Motta and Dr. C. Guillemninault mentioned that people with sleep apnea may develop hypercapnia and hypoxemia when they are asleep. This is closely associated with pulmonary arterial pressure and increases the risk of cardiac arrhythmias or irregular heartbeat.
As per this study, there was mounting evidence that cardiovascular diseases and snoring are interlinked. Plenty of cross-section surveys have found that ischemic cardiac disease, hypertension and angina pectoris have a close association. A case-controlled study with patients that had suffered a stroke were found to be snorers (2-8) while it was 10-8 for habitual or regular snoring. However, it was not clear whether snoring was related to the cardiac diseases without the people suffering with hypertension or those snorers without sleep apnea were equally at risk.
Methods Of The Study
Additionally, over the period of time, postal questionnaires were sent to the study participants. It was asked whether they had been diagnosed with angina pectoris, hypertension or myocardial infarction, as per a doctor. They were asked about the details of the hypertension medication that was prescribed. They were classified into 3 categories:
- If they were under drug medication for treatment of hypertension
- If they had temporary hypertension but were not under drug treatment
- If they did not have history of high blood pressure
All three categories of case subjects got their height and weight recorded and BMI was calculated based on it. Additionally, they were further categorized into two groups- non-smokers, past smokers (2873) and occasional smokers in one category and current smokers that numbered 1384 were in the second group. Additionally, alcohol intake on a regular basis was also noted for both the groups.
To know the number of men that had stroke or developed cardiac diseases in the following years was noted from the Finnish hospitals discharge registers from October 1981 to December 1983. Comparing the results and health status of each category and sub-groups were done on the logistic models. The adjustments were made on the basis of:
- History of high blood pressure or hypertension
- Age of the participant
- Body mass index (BMI)
- Smoking status
- Amount of alcohol intake
Additionally, the study did an analysis of men that did not have any cardiac issues (who had not reported any myocardial infarction or angina pectoris when the study started) and those that did have heart issues. As per the age adjusted related risk, the ischemic heart disease based on hospital/death between non-snorers and frequent snores was 1 per 91 men.
Of the total 462 men that reported myocardial infarction or angina pectoris, only 80 men reported ischemic heart disease while stroke was reported by 10 men. During the 35-month duration of the study, habitual snorers were more at risk of ischemic heart disease than non-snorers with a ratio of 1-30. In the follow up months. 48 men died due to ischemic heart disease. 2 men were non-snorers, 19 of them were habitual snorers, and 27 were occasional snorers.
Analysis Of Case Data
Although as per the data, deaths due to ischemic heart disease was 100,000 per year, but in the cohort, within the age group of 40-49 years was 155, those in the age of 50-59 years group, it was 509 and in the age group of 60-69 years, was 806 in 1982. While the mortality from ischemic heart disease in frequent snorers was 503, occasional snorers that died numbered 354 and non-snorers were 143 men.
Although the data was studied in cross-section, the results of the study indicated that habitual/ frequent snorers were at greater risk of developing myocardial infarction. However, the co-relation between ischemic disease and snoring was not directly related to BMI, smoking, alcohol use, and hypertension. Healthy men that snored and had no history of angina pectoris or myocardial infarction were at risk of developing ischemic heart disease.
As per the analyzed data, the results showed that the role of snoring as a risk element reduced after the ischemic heart disease was diagnosed as other risk factors were enhanced. Incidents of ischemic heart disease was 17% with men with cardiac issues in the past while those developing the disease though with no past cardiac issues was 2%.
Risk Of Stroke with Snoring
As per the results of the study, snoring is associated with risk of having a stroke. Yet, it was not possible to get the exact calculations as there was no case of stroke in the snorers and non-snorers, while they were under this study. Thus, the risk was small between non-snorers and snorers of 1-2% vs 1 -0%.
Why Is Snoring Associated with Ischemic Heart Disease?
In the study, under the guidance of Dr. Markku Koskenvuo, Dr. Jaako Kaprio and their team at the University of Helsinki, as per the knowledge of pathophysiology of sleep apnea, it was seen that the increase in risk of developing cardiovascular disease in snorers was due to obstructive sleep apnea.
Obstructive sleep apnea leads to total collapse of upper airways when the individual is asleep. However, the duration and frequency of sleep apnea varies among people. Few people experience over 300 apneic episodes in a night so the blood oxygen saturation drops significantly, sometimes below 70% while average is 95%.
This leads to temporary increase in the systemic and pulmonary arterial pressure that strains the heart. Thus, with time, snoring turns out to be detrimental and enhances the risk of developing ischemic heart disease irrespective of BMI, smoking, hypertension and alcohol use.