While some school of thought say sleeping less than six hours a day is a major risk factor for stroke, to others the major risk factors are hypertension, age, high cholesterol, obesity and genetic factor. They say the minor risk factors for developing stroke include being a
male and obstructive sleep apnoea (OSA).
The argument was fuelled by a recent United States study of 5,666 people followed for up to three years, which showed that habitually sleeping less than six hours a night significantly increases the risk of stroke symptoms among middle-age to older adults who are of normal weight and at low risk for OSA.
A stroke, or cerebrovascular accident (CVA), is described as the rapid loss of brain function(s) due to disturbance in the blood supply to the brain. This can be due to ischaemia (lack of blood flow) caused by blockage (thrombosis, arterial embolism), or a haemorrhage (leakage of blood). As a result, the affected area of the brain cannot function, which might result in an inability to move one or more limbs on one side of the body, inability to understand or formulate speech, or an inability to see one side of the visual field.
Several studies have shown that the risk factors for stroke include old age, hypertension (high blood pressure), previous stroke or transient ischemic attack (TIA), diabetes, high cholesterol, cigarette smoking and atrial fibrillation; and that high blood pressure is the most important modifiable risk factor of stroke.
OSA or obstructive sleep apnoea syndrome (OSAS) is a common disorder in the community in Nigeria. Association between hypertension and sleep apnoea/snoring has been described among many population. The association between sleep related breathing disorders and cardiovascular disease is further stressed by reports of a high prevalence of sleep apnoea among patients with hypertension.
Local studies have associated OSAS with increased morbidity and mortality. It is characterized by partial or complete collapse of the upper airways during sleep leading to impaired gas exchange and recurrent arousal from sleep. The reported consequences of OSAS include excessive daytime sleepiness, cognitive dysfunction, impaired work performance, and impairment in health-related quality of life.
Observational and experimental evidence suggests that obstructive sleep apnea may contribute to the development of systemic hypertension, cardiovascular disease, and abnormalities in glucose metabolism.
OSA is insidious and patients are often unaware of the associated symptoms. Cardinal manifestations include loud snoring, witnessed breathing pauses during sleep, fitful sleep quality, and excessive daytime sleepiness. Early recognition and appropriate therapy can ameliorate the neurobehavioral consequences and may also have favourable effects on cardiovascular health.
Habitual snoring is associated with hypertension, cerebrovascular disease and coronary heart disease.
Several reports have shown that the prevalence of snoring among adults varies from different part of the world from five to 44 per cent. In a report from Abuja, overall prevalence of snoring among adults was 31 per cent while the prevalence of clinically Suspected Obstructive Sleep Apneas (CSOSA) was one per cent, (1.9 per cent in males, 0.5 per cent in females).
The U.S. study presented last week at SLEEP 2012 noted that the participants had no history of stroke, transient ischemic attack, stroke symptoms or high risk for OSA at the start of the study.
SLEEP 2012 focused solely on sleep medicine and sleep research.
The researchers from the University of Alabama at Birmingham, United States, recorded the first stroke symptoms, along with demographic information, stroke risk factors, depression symptoms and various health behaviours.
After adjusting for body-mass index (BMI), they found a strong association with daily sleep periods of less than six hours and a greater incidence of stroke symptoms for middle-age to older adults, even beyond other risk factors. The study found no association between short sleep periods and stroke symptoms among overweight and obese participants.
However, Nigerian researchers at the Department of Medicine Ladoke Akintola University of Technology (LAUTECH) Teaching Hospital, Osogbo, Osun State in a study titled “Snoring and obstructive sleep apnoea syndrome among hypertensive Nigerians: Prevalence and clinical correlates” concluded: “This study therefore shows that snoring is a commonly prevalent associated condition among hypertensive subjects in Osogbo, Nigeria. Similarly many of them were found to be at a high risk of OSA.”
The study published in Pan African Medical Journal noted that snoring and clinically suspected OSA were associated with increasing age, body mass index, fasting blood sugar and systolic blood pressure. “Hypertensive subjects with sleep related disorders might therefore have increased cardiovascular risk compared to those without sleep related disorders. Therefore, early identification and management of sleep related disorders such as snoring and obstructive sleep apnoea could further reduce the cardiovascular risk of hypertensive Nigerian subjects.”
The researchers include: Adeseye Abiodun Akintunde; Oluyomi Oluseun Okunola; Rotimi Oluyombo; Yussuf Olatunji Oladosu; and Oladimeji George Opadijo.
Lead author of the U.S. study, Dr. Megan Ruiter, said: “In employed middle-aged to older adults, relatively free of major risk factors for stroke such as obesity and sleep-disordered breathing, short sleep duration may exact its own negative influence on stroke development.
“We speculate that short sleep duration is a precursor to other traditional stroke risk factors, and once these traditional stroke risk factors are present, then perhaps they become stronger risk factors than sleep duration alone.”
But a consultant neurologist and stroke expert at the Lagos University Teaching Hospital (LUTH), Idi-Araba, Prof. Frank Ojini, told The Guardian that duration of sleep is not a major risk factor for stroke. “The major risk factor for stroke include hypertension, age, high lipid or high cholesterol and associated obesity, genetic factor like one having a family history of stroke. Being a black is also a major risk factor.
“There are minor risk factors like being a male. But the known contribution of sleep to stroke is in people who snore excessively that is obstructive sleep apnea. People with the condition actually stop breathing for sometime. But in terms of the amount of sleep, I am not sure one can depend on just one study. It has to be repeated. So I wont really be surprised if less than six hours of sleep caused stroke but I am sure it is a minor factor. It could be a risk factor.”
Ojini, however, said that the amount of sleep required to maintain optimal health depends on individuals. “As you get older you tend to sleep less; the elderly sleep less. The study findings may because age is coming into play, that is older adults naturally sleep less,” the neurologist argued.
To a consultant endocrinologist and diabetes expert at LUTH, Prof. Femi Fasamade, “poor sleep is a risk factor for many conditions including heart diseases and stroke.”
The U.S. researcher said further research might support the results, providing a strong argument for increasing physician and public awareness of the impact of sleep as a risk factor for stroke symptoms, especially among persons who appear to have few or no traditional risk factors for stroke.
Ruiter said: “Sleep and sleep-related behaviours are highly modifiable with cognitive-behavioural therapy approaches and/or pharmaceutical interventions. These results may serve as a preliminary basis for using sleep treatments to prevent the development of stroke.”
Ruiter and colleagues collected their data as part of the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, led by Dr. George Howard of the University of Alabama at Birmingham School of Public Health. REGARDS enrolled 30,239 people ages 45 and older between January 2003 and October 2007, and is continuing to follow them for health changes.
The LAUTECH study revealed that the prevalence of snoring among hypertensive Nigerians was 50 per cent. It also revealed that almost all the hypertensive snorers reported excessive daytime somnolence as predicted using the Epworth sleepiness scale.
The study reads: “Male hypertensive subjects had a significantly higher frequency of snoring than their female counterparts. In men the frequency of snoring was 55 per cent while it was 46.7 per cent among female participants in the study. This is similar to what has been reported among other hypertensive population. The prevalence of snoring among these hypertensive subjects was however greater than that reported among non-hypertensive Nigerians. Also, about 52 per cent of hypertensive subjects were found to be at high risk for having obstructive sleep apnoea in this study. Hypertension is a well-documented risk for developing sleep related difficulties such as sleep apnoea, hypopnoea and snoring.”
The study also revealed that hypertensive subjects with positive history of snoring were significantly older than those without history of snoring. Furthermore, body mass index and fasting blood sugar were significantly higher among hypertensive subjects with history of snoring than those without it. This highlights the fact that hypertensive subjects with OSA likely have increased cardiovascular risk.
According to the study, the prevalence of snoring increased with increasing age group with the highest incidence among those in the sixth decade and the very elderly group (greater than70 years). “This agrees with other studies have shown that obstructive sleep apnoea and snoring are directly related to age. With advancing age, sleep-related difficulties become increasingly common and often manifest as subjective complaints of difficulty falling asleep, reduced duration of night-time awakenings, and the amount of night-time sleep obtained. Mechanisms proposed for the age-related increase in prevalence include increased deposition of fat in the parapharyngeal area, lengthening of the soft palate, and changes in body structures surrounding the pharynx,” the researchers noted.
Several epidemiologic studies have described the higher incidence of snoring and sleep apnoea among men compared to their female counterparts. Several explanations account for this: first, women may be less likely to report classical symptoms such as loud snoring, apnoea, nocturnal sorting or gasping. Secondly, differential response of the bed-partner to the symptoms of obstructive breathing during sleep may also contribute to the clinical under-recognition of the disorder in women.
The study showed that hypertensive who were overweight or obese were more likely to be having sleep related disorders including snoring than those with normal body mass index. Similarly, a higher percentage of overweight and obese subjects were found to be at a high risk of obstructive sleep apnoea using the Berlin questionnaire.
-Chukwuma Muanya
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