Exercise during leisure time prevents sudden cardiac death — Tokai University provides scientific proof

A research group led by Lecturer Shotaro Isozaki from the Department of Forensic Medicine, Tokai University School of Medicine, has scientifically proven that "exercise habits during leisure time dramatically reduce the risk of sudden cardiac death." The study utilized a large-scale survey involving Denmark's personal identification numbers (CPR numbers). This research helps develop knowledge of forensic medicine, which typically focuses on investigating causes of death, into applications in the field of public health and preventive medicine that protects future lives. The findings were published in eClinicalMedicine.

Sudden cardiac death is a serious health challenge, accounting for about 10% of all deaths and 50% of cardiovascular deaths. It is extremely difficult to predict because many of these deaths occur suddenly without warning. Therefore, it is said that the only countermeasure is to prevent the onset of the disease, rather than to treat it after it has occurred.

Although it has been known that exercise is good for cardiovascular disease in general, there is little data worldwide that quantitatively show a long-term association with sudden death, as well as the extent to which sudden death could have been prevented if people had exercised.

The research group conducted a follow-up survey on approximately 10,000 Copenhagen residents from 1991 to 2021. Compared to the "low activity group" (less than two hours of light exercise per week), the risk of sudden cardiac death was significantly lower by about 40% for those with "moderate activity" and about 50% for those with "high activity."

Furthermore, an analysis of the Population Attributable Fraction (PAF) suggested that if society as a whole had eliminated physical inactivity, approximately 33% of sudden cardiac deaths might not have occurred. When activity was reassessed approximately 10 years after the initial study, the most recent activity status was more strongly associated with lower risk. This suggests that "continuing to exercise now" is more directly linked to preventing sudden death than "having exercised in the past."

Saving lives does not require special training. The "high activity level" defined in this study does not refer to intense athletic training, but rather a combination of everyday activities such as walking, cycling, and sports.

The study provides scientific evidence that "leisure-time exercise," which can be done without special equipment, can serve as a powerful defense against sudden death, a condition from which it is otherwise difficult to save a patient.

Isozaki stated: "While facing the diagnosis of sudden death as a forensic pathologist and medical examiner, I have felt frustrated by the inability to fully explain the background of a death from limited information. In Denmark, long-term tracking using personal identification numbers (CPR numbers), which are assigned to all citizens, allows for a high level of diagnostic accuracy and epidemiological data integration for sudden death. Through this international cooperation and collaboration with top-level cardiologists and epidemiologists, we can not only clarify the causes of sudden death but also uncover the underlying lifestyles and preventable factors. I believe we have shown one way in which forensic medicine can evolve into a field that contributes to public health and preventive medicine, moving beyond the boundaries of crime prevention and determining causes of death."

Journal Information
Publication: eClinicalMedicine
Title: Leisure-time physical activity and risk of sudden cardiac death: a 28-year follow-up from the Copenhagen City Heart Study
DOI: 10.1016/j.eclinm.2026.103825