According to an article in AFP, a Japanese research team was led by Dr Nobuo Sasaki of the Hiroshima Atomic Bomb Casualty Council, Japan, on determining what kind of sleep disturbance(s) are related to cardiovascular diseases such as ischemic heart disease and stroke. As Dr Sasaki explains, “[most people know that] poor sleep is associated with cardiovascular diseases such as ischemic heart disease and stroke, but the kind of sleep disturbances that are most risky is not well documented”.
First off, what is known as ischemic heart disease?
Otherwise known as coronary heart disease, or coronary artery disease, the term “ischemic heart disease” refers to heart problems caused by narrowed heart arteries. When these arteries are narrowed, lesser blood and oxygen can reach the heart, and can lead to heart attack.
And whilst the term may be used loosely sometimes, the term ‘poor sleep’, as Dr Sasaki said, “includes too short or too long sleep, a difficulty in falling asleep, and difficulty maintaining sleep.”
As such, to delve deeper into which specific sleep disturbances may be linked to the two conditions, Dr Sasaki and his team looked at 12,876 residents of Hiroshima in Japan – including 6,762 men and 6,114 women – with an average age of 68 years.
In the study, the researchers assessed the sleep habits of the participants using the Pittsburgh Sleep Quality Index (PSQI) questionnaire, which assesses various aspects of sleep quality including subjective poor sleep quality, long sleep latency, short sleep duration, low sleep efficiency, difficulty in maintaining sleep, use of sleeping pills, and daytime dysfunction. Higher scores in the self-reported results of the questionnaire, with a range from 0 to 21, indicated poorer sleep quality, with ‘poor sleep’ defined as a global PSQI score equal to or greater than 6.
The team found that a little over half of the patients with ischemic heart disease (52%), 48% who had stroke, and 37% of patients with no cardiovascular disease suffered from poor sleep. They then extrapolated the analysis with these results, and concluded that poor sleep quality, long sleep latency, low sleep efficiency, and use of sleeping pills were significantly associated with both ischemic heart disease and stroke, whereas difficulty in maintaining sleep, a short sleep duration, and daytime dysfunction were only associated with ischemic heart disease.
As Dr. Sasaki explains, “Difficulty maintaining sleep reflects an increase in sleep fragmentation, which refers to brief moments of waking up and causes overactivity of the sympathetic nervous system and adrenocortical axis.”
Dr. Sasaki concluded that, “Our results support the hypothesis that sleep deterioration may lead to cardiovascular disease. Poor sleep in patients with ischemic heart disease may be characterized by shorter sleep and brief moments of waking up.”