<figure id="attachment_481278" class="wp-caption alignnone" style="width: 1962px;" aria-describedby="caption-attachment-481278"><a href="#" data-ident_hash="ea81cf7f"><img src="https://res.cloudinary.com/fridaydigital/image/private/t_article_image/wpmedia/2026/09/2ddb1672c0502be21b8e62f05a4b3818.jpg" alt=""></a>There are five major diseases that can potentially lead to sudden death.<figcaption id="caption-attachment-481278" class="wp-caption-text">
<h4 dir="auto" data-start="74" data-end="152">① Acute Myocardial Infarction — Severe chest pain is not always present</h4>
The first condition to watch out for is an acute myocardial infarction. This occurs when a coronary artery, which supplies oxygen and nutrients to the heart, becomes blocked, cutting off blood flow to the heart muscle.
“Typical symptoms include severe pain or a feeling of pressure, as though the chest is being squeezed. However, a heart attack does not necessarily mean that you will experience excruciating chest pain. Your chest may feel heavy, you may have difficulty breathing, break out in a cold sweat, or feel nauseated. You may also experience discomfort in your shoulders, arms, back, jaw, or upper abdomen.
Older people and those with diabetes in particular can experience a painless myocardial infarction, in which they feel little or no pain, so the symptoms may not be typical. It is dangerous to assume, ‘My chest doesn’t hurt, so it can’t be my heart.’”
In 2010, when he was 67, Morimoto suffered a heart attack and was taken to the hospital by ambulance. According to reports at the time, he complained of pain from his chest to the upper abdomen at home and contacted his manager himself. He was transported by ambulance and diagnosed with a myocardial infarction.
However, no causal relationship has been established between his previous heart attack and his sudden death this time. Dr. Goto points out the following as a general observation:
“What is frightening about a heart attack is not only the damage it causes to the heart muscle. It can also trigger dangerous arrhythmias such as ventricular fibrillation, which can lead to sudden cardiac arrest. If chest discomfort persists, is accompanied by cold sweats or difficulty breathing, or feels clearly different from anything you have experienced before, do not try to tough it out—go to the hospital immediately.”
<h4 dir="auto" data-start="1968" data-end="2075">② Life-Threatening Arrhythmias — &#8220;I lost consciousness for a moment&#8221; is also an important warning sign</h4>
The second is life-threatening arrhythmias, such as ventricular fibrillation and ventricular tachycardia. The heart contracts regularly in response to electrical signals, pumping blood throughout the body. When these electrical signals become severely disrupted, the heart can no longer pump blood normally.
“Especially in ventricular fibrillation, the heart muscle merely quivers rapidly and can no longer function adequately as a pump. Because blood can no longer reach the brain, the person can lose consciousness within a short period of time, leading to cardiac arrest. Prompt CPR and treatment with an AED are necessary.”
What makes this condition frightening is that it can happen suddenly, but some people do experience abnormalities beforehand.
“Be alert to symptoms such as unusually strong palpitations that you have never experienced before, shortness of breath, dizziness, a sensation that everything is going dark, or fainting. It is dangerous to think, ‘I lost consciousness for a moment, but I came around right away, so I’m fine.’ There may be a serious arrhythmia underlying the fainting.”
The Japanese Circulation Society likewise warns that ventricular fibrillation and ventricular tachycardia can occur against a background of conditions such as myocardial infarction and cardiomyopathy, and encourages people to consult a doctor if they experience new symptoms such as palpitations, shortness of breath, fainting, or dizziness.
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<div data-friday-nextpage-lead="The location of the pain shifts"></div>
<figure id="attachment_481280" class="wp-caption alignnone" style="width: 834px;" aria-describedby="caption-attachment-481280"><a href="#" data-ident_hash="3a7bacb5"><img src="https://res.cloudinary.com/fridaydigital/image/private/t_article_image/wpmedia/2026/09/a7dfd37fba2e93a82e2c9be16b929a4f.png" alt=""></a><figcaption id="caption-attachment-481280" class="wp-caption-text">
<h4 class="PDq2pG_selectionAnchorContainer" dir="auto" data-start="65" data-end="132">③ Acute Aortic Dissection — Sudden severe chest or back pain</h4>
The third is acute aortic dissection. The aorta is the largest blood vessel in the human body and the first vessel through which blood pumped out of the heart passes. An aortic dissection occurs when the wall of the aorta suddenly tears, allowing blood to enter the layers of the vessel wall.
“The typical symptom is sudden, extremely severe pain in the chest or back. People may describe it as pain unlike anything I’ve ever experienced or suddenly feeling as though my chest or back was being torn apart. As the dissection spreads, the pain may move from the chest to the back and even down to the lower back.”
The symptoms are not necessarily limited to the chest or back.
“If blood flow through the vessels supplying the brain is disrupted, it can cause impaired consciousness or paralysis of the limbs. If the blood vessels of the heart are affected, it can result in a condition resembling a myocardial infarction.
“If the aorta ruptures, or if blood accumulates inside the membrane surrounding the heart (the pericardium), preventing the heart from functioning properly—a condition known as ‘cardiac tamponade’—it can lead to sudden death. High blood pressure is a major risk factor for aortic dissection. Aortic dissection is a medical emergency in which every moment counts. Do not ignore sudden, severe chest or back pain by thinking, ‘It’ll probably go away if I rest for a while.’”
<h4 dir="auto" data-start="1553" data-end="1640">④ Pulmonary Thromboembolism — Suddenly having trouble breathing requires caution</h4>
The fourth is pulmonary thromboembolism. A blood clot that forms in a vein in the leg or elsewhere can travel through the bloodstream to the lungs and block a pulmonary artery. When this occurs after remaining in the same position for a long period, it is commonly known as economy-class syndrome.
“The characteristic symptoms are sudden difficulty breathing and chest pain. In severe cases, insufficient blood can reach the lungs, causing blood pressure to drop, which can result in loss of consciousness or cardiac arrest.”
Caution is necessary when someone is in a situation that makes blood clots more likely to form, such as after surgery, prolonged bed rest, or having cancer.
In some cases, this condition first causes abnormalities in the legs before affecting the lungs.
“One leg may suddenly become swollen or painful. If you then suddenly develop difficulty breathing or chest pain, pulmonary thromboembolism should be considered.”
<h4 dir="auto" data-start="2602" data-end="2687">⑤ Subarachnoid Hemorrhage — A headache unlike anything you’ve ever experienced</h4>
Brain disorders can also lead to sudden death. A representative example is subarachnoid hemorrhage. This occurs when an aneurysm or other abnormality in a blood vessel in the brain ruptures, causing bleeding into the subarachnoid space beneath the arachnoid membrane, one of the three layers of membrane covering the brain.
“One extremely important warning sign is a sudden, severe headache. It is often described as a headache unlike anything I’ve ever experienced. It may be accompanied by nausea or vomiting, and in severe cases, the person may lose consciousness on the spot. A relatively mild headache known as a warning headache can also occur before a major hemorrhage.”
People who frequently suffer from headaches need to be particularly cautious.
“It is easy to think, ‘It’s probably just my usual headache again,’ but is it really the same as your usual headache? If the headache is clearly different from what you normally experience, it is important not to simply take a painkiller and wait to see what happens, but to seek medical attention immediately.”
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<div data-friday-nextpage-lead="Don’t judge based on the intensity of the pain alone."></div>
<h2>Don&#8217;t dismiss warning signs as just age</h2>
What should we be mindful of in our daily lives? Dr. Goto advises against judging symptoms based solely on how severe the pain is.
“Just because a disease can lead to sudden death does not mean that severe symptoms will necessarily appear from the outset. Especially as we get older, we tend to think, ‘I’ve been getting tired more easily lately because I’m getting older,’ or ‘My shortness of breath is just due to my age.’
If you suddenly become short of breath after walking a distance that you used to be able to manage without any problem, experience an unusual sensation in your chest that you have never had before, or repeatedly experience palpitations—if you notice any changes that are different from how you normally are, I want you to stop and take notice.”
Symptoms that require immediate attention include sudden severe chest pain or a feeling of pressure in the chest, sudden severe difficulty breathing, fainting, a sudden severe headache, impaired consciousness, or paralysis on one side of the body.
“It is dangerous to think, ‘I’ll wait until morning,’ or ‘It’ll probably get better if I sleep for a while.’ With conditions such as myocardial infarction, aortic dissection, and subarachnoid hemorrhage, the time until treatment begins is extremely important. If you are unsure whether you should call an ambulance, consult your local emergency medical consultation service, such as #7119.”
It is also important to notice when something is wrong with someone around you.
“If someone collapses in front of you, is unresponsive, and is not breathing normally, immediately call 119 and do not hesitate to perform chest compressions or use an AED. The actions of bystanders can help save a life.”
Just because someone was healthy until yesterday does not necessarily mean they are safe. That does not mean, however, that you need to live in fear of every change in your body. Dr. Goto concluded:
“Not all sudden deaths are preceded by warning signs. Some cases truly occur suddenly and are difficult to predict. Therefore, it is also incorrect to think that sudden death can be prevented if you just know the warning signs. What is important is not to dismiss anything in your body that is ‘different from usual.’
“Don’t simply assume, ‘I’m just tired,’ ‘It’s because I’m getting older,’ or ‘I’ll feel better after I sleep.’ If a concerning symptom persists, seek medical attention. If you suddenly develop severe symptoms, don’t hesitate to consider calling an ambulance. That can help protect your life.”
“I was healthy until yesterday, so I’ll be fine today.”
There are diseases for which that assumption does not hold. Sudden chest pain, difficulty breathing, fainting, a severe headache unlike anything you have experienced before—
Not overlooking the SOS signals from your body that are different from usual is the first step toward protecting your own life and the lives of those close to you.
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 Kyodo News (first photo), Hide Nishihara

 Leo Morimoto, who was active as an actor and narrator, has died suddenly. According to his agency, the cause is “unknown.” How should we prepare for sudden death, which can happen to anyone at any time? A specialist explains.

Leo Morimoto Dies Suddenly From an Unknown Cause—Doctors Warn of 5 Deadly Diseases and the Warning Signs You Shouldn’t Ignore

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