In our study, we started this work to determine the features of sudden death in young adults in the study population and to determine the etiologies of sudden death in this age interval. In this series, sudden death in young adults occurs mainly due to cardiovascular diseases, especially related to myocardial ischemia in male subjects. In addition, sudden death was in the morning and early in the week. It was more common in summer. Sudden death is most often the first manifestation of pathologies, especially unsuspected heart diseases.
The predominance of cardiovascular causes is the common denominator of almost all studies reported in the literature. The understanding of the sudden death of the young adult is interesting to develop prevention strategies. Indeed, the etiologies are very variable. They differ according to the studied population (age, sex, ethnic origin, diet ...).
For clinicians, sudden death means sudden cardiac death, while forensic pathologists include under this term the etiologies of natural death that could manifest as sudden death. The natural character of the death thus demonstrated by the autopsy supplemented by the toxicological, and anatomo-pathological examinations ranks the death within the framework of the sudden death. This problem of definition has been examined by an international committee convened by the Scientific Council on Arteriosclerosis and Ischemic Heart Disease of the International Society of Cardiology, and the Council of Arteriosclerosis and Epidemiology of the American Heart Association. This committee proposed the definition that was later adopted by the World Health Organization . In our study, the inclusion criteria used the most recognized definition of sudden death in general, which is that of the World Health Organization.
Sudden death of the young adult in itself was rarely studied as a separate entity. The majority of studies were limited to one age group (sudden death in infants ...) or a particular group of people (sudden death in athletes, sudden death in the military, sudden death instead of work ...) with the possible risk of selection bias.
The second problem that is encountered is the divergence in studies that define "young adult". In our study, we saw the utility of grouping all subjects aged 18 to 35 years. The choice of the upper age limit at age 35 is identical to the majority of articles in the literature [2,8,9].
The incidence studies were divergent since the sample was not the same for inclusion ages. In a 10-year US College of Cardiology (2000-2010) study of subjects performing military service, the incidence of sudden death was 3.25/100,000 for subjects aged 18 to 35 years old . This incidence was at 2.68 in Ireland . There is indeed a divergence in the incidence. This wide divergence shows that the incidence of sudden death, including that of the young adult, is dependent on the specific geographical, ethnic, socioeconomic factors of each country .
In the current study, the average age was 26.4 years old. In general, sudden death spares no age range . Nevertheless, two peak frequencies were noted in our study population at 21 (6.4%), and 35 (7.7%), respectively. In a Danish study, the peak frequency was at the age of 35 years old . In a Danish nationwide cohort of persons aged <50 years, the annual incidence rate of sudden cardiac death was of almost 10 times higher in persons aged 36 to 49 years than in persons aged 1 to 35 years .
The peaks already described could be explained by the hyperactivity of the population at these ages associated with a change in the habits of life of the subjects with mostly the consumption of alcohol, and tobacco and exposure to stress. These united factors favour decompensating a probable heart disease until there unknown. Indeed, the older the age, the more the risk of sudden death increases as risk factors accumulate .
In our study, the sex ratio was 3.6. In all published studies, there is still a male predominance of sudden death of the young subject. This predominance varies from one study to another, and is between 83% and 100% [11,12]. In the FRAMINGHAM study , the risk of sudden cardiac death in adults was higher in men (2/3) than in women (1/3), and correlated with high blood pressure, left ventricular hypertrophy, overweight and smoking intoxication . This male predominance was addressed in several studies. Indeed, testosterone may be a cardiovascular risk factor for men, while oestrogen plays a protective role for women . In the Fingesture study, women were considerably older at the time of sudden death, and more commonly had non-ischemic causes. Women were also more likely to have a prior normal clinical finding than men, but an increased biological marker for sudden death risk criteria for left ventricular hypertrophy with repolarization abnormalities was more commonly observed in women .
In addition to these non-modifiable risk factors (sex, hormones, etc.), lifestyle also seems to be implicated in the male predominance of sudden death. Smoking, and alcohol use, affecting men more than women, appear to be factors contributing to this inequality .
In this work, a family history of sudden death was noted only in 7 cases (5.1%). Medical history of sudden death in the family has been variable in the literature between 1.38%, and 5.26%. The presence of a family history of sudden death is contributing for some pathologies such as hypertrophic cardiomyopathy, arrhythmogenic dysplasia of the right ventricle, coronary malformations, and long QT syndrome .
In a prospective study in France, a significant correlation between the antecedent of sudden death in the family, and the risk of its occurrence in another member was found . The FRAMINGHAM study  showed that the occurrence of coronary death in a parent increased by 30% the risk of coronary heart disease in children.
How could these subjects survive asymptomatic until sudden death? Is there a problem in the interrogation? Whatever the problem, these findings lead us to recommend a better interview with the parents, although they are in such conditions still in shock.
A sports activity is reported in only 4 cases in our study series. It is thought that this figure is underestimated because it is not given much interest in memorials. In our study, death occurred during physical activity in 15 cases. It is recognized that regular physical exercise requires long-term cardiovascular protection . Another Italian study by Corrado  showed different results; the risk of sudden death on exertion is more frequent (double) for young athletes than for non-athletes of the same age. He explains this result by the phenomenon of "burn out" or "negative overtraining" . Death during physical activity often occurs during the recovery period . In a British study, only 20% of hypertrophic cardiomyopathy patients were diagnosed during life, underscoring how often the disease is not identified during life, and sudden cardiac death can be the first manifestation. Moreover, the majority of sudden cardiac death events occurred at rest, and some even during sleep; the variables associated with death during exercise were young age, and male sex .
As in our study, the summer predominance is comparable to that found in the literature [22,23]. This slight predominance of cases of sudden death during the summer may be related to the excessive heat in our country at this time of year (from June to October). The seasonal variation in the incidence of sudden death in a Japanese population showed that it increased in agricultural workers in April, and September and employees in March, and September . This could be explained by the stress encountered by each type of work. In addition, the Gulf region and Malaysia, are known to be hot countries, and daily workers does not have enough rest in Summer [23,25]. A majority of them comprises labourers, factory workers, drivers and so on (30.6%). This group has lower income compared to other groups. Due to the ﬁnancial problem, they might not get a regular medical check-up for early detection of their diseases or even treatment for their diseases .
The distribution of deaths by day of the week showed a peak frequency for Tuesday. This could be related to the return to work as well as stress submission after weekend rest. In our series, two frequency peaks during the day were noted at 7 am, and 8 am. Sudden death was more common between 4 am, and 11 am (48.7%). The concept of circadian variation in sudden death was also noted in the FRAMINGHAM study  with a risk of sudden cardiac death 3 times greater in the morning than in the evening.
In our study, most deaths occurred at rest (or minimal daily activity). This result is consistent with the majority of studies published in the literature [8,19-21]. This predominance could be explained by the fact that in the indeterminate forms of death, and hypertrophic cardiomyopathy, the death is rather the consequence of a rhythm disorder whose occurrence is often at rest or during sleep.
In our study, faintness is described as a premonitory sign in 59.1% of cases. There is a divergence in the frequencies described by the different studies. This can be explained by a terminology problem . Indeed, the meaning of the word "faintness" is a bit vague for the forensic scientist as well as for the testimony.
Cardiovascular origin is at the top of the list of etiologies of sudden death in young adults. This predominance of cardiovascular causes of sudden death is the common denominator of all series reported in the literature, regardless of the demographic, and geographical characteristics of the study population. The cardiovascular causes of sudden death, in general, are different according to the age group. Indeed, in young people (<35 years), it is the primary cardiomyopathies, and cardiac arrhythmias most frequently incriminated in sudden death .
In our study, ischemic heart disease is responsible for sudden death in 32.3% of cases. Ischemic heart disease in young adults takes on a particular aspect. Indeed, it is not necessarily coronary atherosclerosis at the origin of ischemic heart disease. In addition to "major" malformations, which are symptomatic from an early age, or sometimes in adolescents or young adults, certain "minor" abnormalities remain silent . An American study on military subjects (age <35 years) showed a probable cardiac origin in 41.3% of cases, coronary artery disease in 23.2% of cases, and hypertrophic cardiomyopathy in 12.8% of cases.
In the current study, in 9.5% of the cases, the autopsy, and the complementary investigations did not yield to make a certain diagnosis. The percentage of obscure autopsies or when the observed lesions do not sufficiently explain the death varies from one study to another. This variation in the percentage depends on the means of complementary examinations used. This percentage is also variable according to the age group. After reviewing the literature, the obscure autopsy is noted in 20%, and 26% [2,3].
This can be explained by the difference between the age groups studied. Death by inhibition is a suspicious death, given the more or less accidental nature of the inhibition that may be consecutive to trauma: boxing, judo, stroke, puncture, abortion, drowning ... . The essential functional sudden death represents 1 to 17% according to the series .
At present, and especially in those cases where the classical autopsy is unable to determine a certain cause of death, we can no longer speak of a forensic autopsy in this context without resorting to genetic investigations. Indeed, deaths attributable to cardiac arrhythmia, dysfunction of the electrical system of the heart are often hereditary in nature. The diagnosis cannot be made during the traditional autopsy, because the cardiac tissue may be free of any visible sign, hence the need for a genetic autopsy . The results of the autopsy were negative. Then, death is often attributable to an arrhythmia that leaves no identifiable sign in the heart tissue. Most of the disorders that affect the heart's electrical system are related to an inherited genetic abnormality, which can be found in many members of the same family. Given the often-asymptomatic nature of these disorders, their first manifestation may be a fatal cardiac event. However, there is a recruitment bias since cases where a pathological examination was not performed, and when the forensic record did not have enough information were eliminated.
Among the limitations of our study, the genetic investigation focused on heart tissue was not performed. Molecular autopsy plays an important role in characterizing the existence of a certain genetic determinism of sudden death in young adults. There was sometimes a lack of data on the deceased's medical history. In addition, this series does not cover all the cases of sudden death in the region of Monastir. In this situation, we cannot talk about epidemiological findings.