Mortality (from lat. Mortalitas "mortality"), mortality rate , mortality or death rate are terms from demography . They denote the number of deaths in relation to the total number of individuals or - in the case of the specific death rate - in relation to the number in the relevant population , usually in a certain period of time. The mortality in terms of the probability of death can be found in the first column of each mortality table .
The death rate or mortality rate is the ratio of the number of deaths to the average population of a population.
The crude mortality is the number of deaths per population per time, for example per 1,000 people and a year. The age-specific mortality, for example child mortality , indicates the deaths per age group per time. Lethality is the mortality related to the total number of people suffering from a disease. In the case of infant or maternal mortality , the number of events (births) is the reference value, not the population size.
In epidemiology , (disease-specific) mortality is the ratio of the number of individuals who have died of a disease in a population in a period of time to the number of individuals in the population (usually based on 100,000 inhabitants). The mortality rate , however, is the ratio of the number of deaths from a particular disease to the number of individuals with the disease individuals.
According to the birth risk, the death rate drops to its minimum value for eight to ten year olds with approx. 20 deaths per 100,000 people of the age group per year (tpj = deaths per year (per 100,000 people)), see diagram. At almost 50%, accidents are the most common cause of death in this age group. For 15 to 20 year olds, accidents are also the main risk (40 tpj ), followed by murder (approx. 18 tpj for the USA, 40 tpj for South Africa, 5 tpj for Germany) and suicide (12 tpj ). With increasing age, the suicide rate and the frequency of accidents remain almost unchanged, while illnesses make up the main part of the death rate of 800 tpj among 50 to 60 year olds.
Abraham de Moivre (1725) approximated the age-dependent mortality rate through a hyperbolic increase in the risk of death, limited by a maximum age. Benjamin Gompertz (1824) suggested an exponential increase in mortality, which reflects the observed data well from the age of 30. Refined models introduce additional parameters.
Modeling according to Gompertz
In the Gompertz diagram (see mortality curve above) the logarithm of the death rate is plotted against age. The logarithmic representation shows that from the age of approx. 30 the increase is almost linear: the death rate doubles approximately at constant time intervals. This period of time is also abbreviated as MRDT from mortality rate doubling time (or MRD). The linear increase in the logarithmic representation corresponds to an exponential increase in the death rate with age. Mathematical modeling typically uses the natural logarithm, so the death rate is described as follows:
It denotes the mortality at the age of 30 years. An adjustment for the parameter provides a value of , which corresponds to an MRDT of years. The factor is called the Gompertz death coefficient. Studies have shown that the MRDT has typically been between 7 and 9 years in Australia, the United States, Japan, and Northern Europe from the mid-18th century to today. Therefore the value is often estimated at 8.
For comparison, MRDT values for other animal species are: laboratory mouse 0.27 years, laboratory hamster 0.5, rhesus monkey 15, horse 4, domestic dog 3, black-backed gull 5, king pheasant 1.6 years.
Examples of mortality
- Intrauterine or fetal mortality refers to the time of pregnancy, it includes miscarriages, stillbirths, and terminations.
- Premature infant mortality or neonatal mortality is a subset of infant mortality (1st to 4th month).
- Perinatal mortality is the sum of neonatal and fetal mortality, reduced in various ways by phases of the onset of pregnancy of different lengths, according to WHO 22 weeks. In 2006 it was 0.3% (Luxembourg), 0.5% (Germany), 1% (France) and 1.5% (Macedonia) of births for fetuses weighing at least 1 kg and up to 6 days after birth .
- Infant mortality around 2000 in Germany: 400 deaths per 100,000 births = 4 per 1000 = 1/250.
- Maternal mortality at birth in 2003 in Germany: 12 per 100,000 women giving birth, at birth in 2003 in Kenya: 1,300 per 100,000.
- Mortality in Germany: 1,000 deaths per 100,000 inhabitants per year = 10 per 1,000 = 1/100.
- Road mortality 2004: deaths per 100,000 inhabitants per year: 8 in Germany, 5 in the Netherlands.
- Fatalities from lightning strikes in Germany nowadays: an average of three to seven deaths per year in Germany, i.e. less than 0.01 per 100,000 inhabitants per year In the 19th century, around 300 people were killed by lightning in Germany each year, as significantly more people were out Worked in the field and could not retreat into protected objects such as cars, tractors or combine harvesters.
The mean life expectancy is better suited to the comparison of different regions than the general or raw mortality , since it compensates for the possibly different age structure composition of the population. In relation to the age structure , very different populations also have very different mortality rates.
A general probability of death is often derived from the mortality / year for a risk assessment. For example, in Germany with a population of 80 million, around five people die each year from lightning strikes. Assuming an age of 80 years, the risk of dying from lightning within the 80 years is 1: 200,000. The risk of traffic accidents in Germany is accordingly 1: 150. After all, the general risk of dying within 80 years of life is 1: 1.25 = 80%.
The main influencing factors for mortality are:
- Ecological determinants (especially the environment, precaution against natural disasters)
- Socio-economic, political and cultural determinants (physical work, occupational safety, income, nutrition, lifestyle, war, traffic, ...)
- Medical determinants (e.g. genetic factors, quality of medical care, vaccinations, health education, hygiene regulations, etc.)
- While it averages out statistically, chance remains as fate for the individual: luck and unhappiness.
The standardized mortality rate deals with the data on the deaths of groups of people, which are made mathematically comparable with regard to age, gender, etc.
The death rate plays a role in estimating seasonal flu and pandemics . The mortality is compared with the mean values of previous years without the epidemic and in this way excess mortality is determined that can be assigned to the epidemic. From 2008 DG Sante supported the establishment of the Euromomo project for pan-European monitoring of mortality. It collects data from 18 European countries, the four parts of the United Kingdom and two German federal states continuously and promptly in order to make the effects of seasonal influenza or a pandemic on mortality rates visible across national borders. The project is now also receiving support from the European Center for Disease Prevention and Control (ECDC) and the World Health Organization (WHO).
- Morbidity - incidence of illness
- Relative and absolute risk reduction
- Number of treatments required
- Micromort , unit of measure for the risk of death
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