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World infant mortality rates in 2008^[1]

In the field of public health, infant mortality is a commonly used statistical measure that is defined as the ratio of infant deaths to live births.

Traditionally, the most common cause worldwide was dehydration from diarrhea, however a variety of programs combating this problem have decreased the rate of children dying from dehydration. As a result, the most common cause is now pneumonia. Other major causes of infant mortality include: malnutrition, malaria, congenital malformation, infection and SIDS.

In reliability engineering, "infant mortality" is the failures that occur in the first part of the bathtub curve.

Common definitions[link]

The most widely used definition of Infant mortality rate (IMR) is the number of deaths of babies under one year of age per 1,000 live births. The rate in a given region, therefore, is the total number of newborns dying under one year of age divided by the total number of live births during the year, then all multiplied by 1,000. The infant mortality rate is also called the infant death rate (per 1,000 live births).

Historically, infant mortality claimed a considerable percentage of children born, in the 1850s in America it was estimated to be 216.8 per 1,000 for whites and 340.0 for African Americans but rates have significantly declined in the West in modern times. This has been mainly due to improvements in basic health care, though high-technology medical advances have also helped. Infant mortality rate is commonly included as a part of standard of living evaluations in economics.^[2]

Global infant mortality trends[link]

For the world, and for both Less Developed Countries (LDCs) and More Developed Countries (MDCs), IMR declined significantly between 1960 and 2001. According to the Save the Children State of the World's Mothers report, the world infant mortality rate declined from 126 in 1960 to 57 in 2001.^[4]

However, IMR was, and remains, higher in LDCs. In 2001, the Infant Mortality Rate for Less Developed Countries (91) was about 10 times as large as it was for More Developed Countries (8). For Less Developed Countries, the Infant Mortality Rate is 17 times as high as it is for More Developed Countries. Also, while both LDCs and MDCs made dramatic reductions in infant mortality rates, reductions among less developed countries are, on average, much less than those among the more developed countries.

Nearly two orders of magnitude separate countries with the highest and lowest reported infant mortality rates. The top and bottom five countries by this measure (taken from The World Factbook's 2009 estimates) are shown below.

Afghanistan's infant mortality rate is expected to improved by at least 60% in the next ten years due to billions of dollars of international aid.^[5]

Socio-economic factors[link]

Social class is a major factor in infant mortality, both historically and today. Over the period between 1912 and 1915, the Children’s Bureau examined data across eight cities and nearly 23,000 live births.^[6] They discovered that lower incomes tend to correlate with higher infant mortality. If the father had no income, the rate of infant mortality was 357% more than that for the highest income earners ($1,250+).^[6] As well, differences between races were apparent during this time period. African-American mothers experience an infant mortality at a rate 44% higher than average.^[6]

While infant mortality is normally negatively correlated with GDP, there may indeed be some opposing short-term effects to a recession. A recent study by The Economist shows that economic slowdowns reduce the amount of air pollution, which results in a lower infant mortality rate. During the late 1970s and early 1980s, the recession’s impact on air quality is estimated to have saved around 1,300 US babies.^[7] It is only during deep recessions that infant mortality increases. According to Norbert Schady and Marc-Francois Smitz, recessions where GDP per capita drops by 15% or more have a negative impact on infant mortality.^[8]

Comparing infant mortality rates[link]

The infant mortality rate correlates very strongly with, and is among the best predictors of, state failure.^[9] IMR is therefore also a useful indicator of a country's level of health or development, and is a component of the physical quality of life index. However, the method of calculating IMR often varies widely between countries, and is based on how they define a live birth and how many premature infants are born in the country. The World Health Organization (WHO) defines a live birth as any born human being who demonstrates independent signs of life, including breathing, voluntary muscle movement, or heartbeat. Many countries, however, including certain European states and Japan, only count as live births cases where an infant breathes at birth, which makes their reported IMR numbers somewhat lower and raises their rates of perinatal mortality.^[10]

The exclusion of any high-risk infants from the denominator or numerator in reported IMRs can be problematic for comparisons. Many countries, including the United States, Sweden and Germany, count an infant exhibiting any sign of life as alive, no matter the month of gestation or the size, but according to United States Centers for Disease Control (CDC) researchers,^[11] some other countries differ in these practices. All of the countries named adopted the WHO definitions in the late 1980s or early 1990s,^[12] which are used throughout the European Union.^[13] However, in 2009, the US CDC issued a report that stated that the American rates of infant mortality were affected by the United States' high rates of premature babies compared to European countries. It also outlined the differences in reporting requirements between the United States and Europe, noting that France, the Czech Republic, Ireland, the Netherlands, and Poland do not report all live births of babies under 500 g and/or 22 weeks of gestation.^{[11][14][dead link][15]} The report concluded, however, that the differences in reporting are unlikely to be the primary explanation for the United States’ relatively low international ranking.^[15]

Another well-documented example also illustrates this problem. Until the 1990s, Russia and the Soviet Union did not count, as a live birth or as an infant death, extremely premature infants (less than 1,000 g, less than 28 weeks gestational age, or less than 35 cm in length) that were born alive (breathed, had a heartbeat, or exhibited voluntary muscle movement) but failed to survive for at least seven days.^[16] Although such extremely premature infants typically accounted for only about 0.5% of all live-born children, their exclusion from both the numerator and the denominator in the reported IMR led to an estimated 22%-25% lower reported IMR.^[17] In some cases, too, perhaps because hospitals or regional health departments were held accountable for lowering the IMR in their catchment area, infant deaths that occurred in the 12th month were "transferred" statistically to the 13th month (i.e., the second year of life), and thus no longer classified as an infant death.^[18]

UNICEF uses a statistical methodology to account for reporting differences among countries:

Another challenge to comparability is the practice of counting frail or premature infants who die before the normal due date as miscarriages (spontaneous abortions) or those who die during or immediately after childbirth as stillborn. Therefore, the quality of a country's documentation of perinatal mortality can matter greatly to the accuracy of its infant mortality statistics. This point is reinforced by the demographer Ansley Coale, who finds dubiously high ratios of reported stillbirths to infant deaths in Hong Kong and Japan in the first 24 hours after birth, a pattern that is consistent with the high recorded sex ratios at birth in those countries. It suggests not only that many female infants who die in the first 24 hours are misreported as stillbirths rather than infant deaths, but also that those countries do not follow WHO recommendations for the reporting of live births and infant deaths.^[20]

Another seemingly paradoxical finding is that when countries with poor medical services introduce new medical centers and services, instead of declining the reported IMRs often increase for a time. This is mainly because improvement in access to medical care is often accompanied by improvement in the registration of births and deaths. Deaths that might have occurred in a remote or rural area, and not been reported to the government, might now be reported by the new medical personnel or facilities. Thus, even if the new health services reduce the actual IMR, the reported IMR may increase.

Infant mortality rate in war[link]

In most cases, war-affected areas will experience a significant increase in infant mortality rates. The primary causes of the increase are external factors such as murder and abuse. However, many other significant factors influence infant mortality rates in war-torn areas. Health care systems in developing countries in the midst of war often collapse. Attaining basic medical supplies and care becomes increasingly difficult. During the Yugoslav Wars in the 1990s Bosnia experienced a 60% decrease in child immunizations. Preventable diseases can quickly become epidemic given the medical conditions during war.^[21]

Many developing countries rely on foreign aid for basic nutrition. Transport of aid becomes significantly more difficult in times of war. In most situations the average weight of a population will drop substantially.^[22] Expecting mothers are affected even more by lack of access to food and water. During the Yugoslav Wars in Bosnia the number of premature babies born increased and the average birth weight decreased.^[21]

There have been several instances in recent years of systematic rape as a weapon of war. Women who become pregnant as a result of war rape face even more significant challenges in bearing a healthy child. Studies suggest that women who experience sexual violence before or during pregnancy are more likely to experience infant death in their children.^[23][24][25] Causes of infant mortality in abused women range from physical side effects of the initial trauma to psychological effects that lead to poor adjustment to society. Many women who became pregnant by rape in Bosnia were isolated from their hometowns making life after childbirth exponentially more difficult.^[26]

See also[link]

• List of countries by infant mortality rate
• Diarrheal diseases
• Childlessness
• Rotavirus
• Pneumonia
• Pneumococcal disease

Related statistical categories:

• Perinatal mortality only includes deaths between the foetal viability (22 weeks gestation) and the end of the 7th day after delivery.
• Neonatal mortality only includes deaths in the first 28 days of life.
• Postneonatal mortality only includes deaths after 28 days of life but before one year.
• Child mortality includes deaths within the first five years after birth.

References[link]

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2012)

External links[link]

Wikimedia Commons has media related to: Infant mortality

• The State of the World's Children 2008: Child Survival
• Infant mortality on the Children's Rights Portal
• Infant mortality rate - Country comparison
• The World Health Report 2005 – Make Every Mother and Child Count
• World Health Statistics - Probability of dying (per 1000) under age five years (under-5 mortality rate)
• World Health Statistics - Neonatal mortality rate (per 1000 live births)
• Born in Bradford - a 2006 UK-based research cohort study investigating the causes of infant mortality and low birth rate in Bradford, UK.
• State of the World's Mothers 2006 Up to date 2006 analysis of infant mortality rates published by Save the Children.

Crude death rate by country.

Mortality rate is a measure of the number of deaths (in general, or due to a specific cause) in a population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of deaths per 1000 individuals per year; thus, a mortality rate of 9.5 (out of 1000) in a population of 100,000 would mean 950 deaths per year in that entire population, or 0.95% out of the total. It is distinct from morbidity rate, which refers to the number of individuals in poor health during a given time period (the prevalence rate) or the number of newly appearing cases of the disease per unit of time (incidence rate). The term "mortality" is also sometimes inappropriately used to refer to the number of deaths among a set of diagnosed hospital cases for a disease or injury, rather than for the general population of a country or ethnic group. This disease mortality statistic is more precisely referred to as "case fatality".

One distinguishes:

1. The crude death rate, the total number of deaths per year per 1000 people. As of July 2009^[update] the crude death rate for the whole world is about 8.37 per 1000 per year according to the current CIA World Factbook.^[1]
2. The perinatal mortality rate, the sum of neonatal deaths and fetal deaths (stillbirths) per 1000 births.
3. The maternal mortality ratio, the number of maternal deaths per 100,000 live births in same time period.
4. The maternal mortality rate, the number of maternal deaths per 1,000 women of reproductive age in the population (generally defined as 15-44 years of age) .
5. The infant mortality rate, the number of deaths of children less than 1 year old per 1000 live births.
6. The child mortality rate, the number of deaths of children less than 5 years old per 1000 live births.
7. The standardised mortality ratio (SMR)- This represents a proportional comparison to the numbers of deaths that would have been expected if the population had been of a standard composition in terms of age, gender, etc.^[2]
8. The age-specific mortality rate (ASMR) - This refers to the total number of deaths per year per 1000 people of a given age (e.g. age 62 last birthday).

In regard to the success or failure of medical treatment or procedures, one would also distinguish:

1. The early mortality rate, the total number of deaths in the early stages of an ongoing treatment, or in the period immediately following an acute treatment.
2. The late mortality rate, the total number of deaths in the late stages of an ongoing treatment, or a significant length of time after an acute treatment.

Note that the crude death rate as defined above and applied to a whole population can give a misleading impression. The crude death rate depends on the age (and gender) specific mortality rates and the age (and gender) distribution of the population. The number of deaths per 1000 people can be higher for developed nations than in less-developed countries, despite life expectancy being higher in developed countries due to standards of health being better. This happens because developed countries typically have a completely different population age distribution, with a much higher proportion of older people, due to both lower recent birth rates and lower mortality rates. A more complete picture of mortality is given by a life table which shows the mortality rate separately for each age. A life table is necessary to give a good estimate of life expectancy.

Statistics[link]

During ancient times and the Middle Ages, the crude death rate was about 40 deaths per year per 1,000 people.^{[citation needed]}

The ten countries with the highest crude death rate, according to the 2009 CIA World Factbook estimates, are:

Rank	Country	Death rate (annual deaths/1000 persons)
1	Swaziland	30.83
2	Angola	24.08
3	Lesotho	22.20
4	Sierra Leone	21.91
5	Zambia	21.34
6	Liberia	20.73
7	Mozambique	20.07
8	Afghanistan	19.18
9	Djibouti	19.10
10	Central African Republic	17.84

See list of countries by death rate for worldwide statistics.

According to the World Health Organization, the 10 leading causes of death in 2002 were:

1. 12.6% Ischaemic heart disease
2. 9.7% Cerebrovascular disease
3. 6.8% Lower respiratory infections
4. 4.9% HIV/AIDS
5. 4.8% Chronic obstructive pulmonary disease
6. 3.2% Diarrhoeal diseases
7. 2.7% Tuberculosis
8. 2.2% Trachea/bronchus/lung cancers
9. 2.2% Malaria
10. 2.1% Road traffic accidents

Causes of death vary greatly between first and third world countries. See list of causes of death by rate for worldwide statistics.

Scatter plot of the natural logarithm of the crude death rate against the natural log of per capita real GDP. The slope of the trend line is the elasticity of the crude death rate with respect to per capita real income. It indicates that a 10% increase in per capita real income is associated with a 1.5% decrease in the crude death rate. Source: World Development Indicators.

According to Jean Ziegler (the United Nations Special Rapporteur on the Right to Food for 2000 to March 2008), mortality due to malnutrition accounted for 58% of the total mortality in 2006: "In the world, approximately 62 millions people, all causes of death combined, die each year. In 2006, more than 36 millions died of hunger or diseases due to deficiencies in micronutrients".^[4]

Of the roughly 150,000 people who die each day across the globe, about two thirds—100,000 per day—die of age-related causes.^[5] In industrialized nations, the proportion is much higher, reaching 90%.^[5]

See also[link]

• Biodemography
• Birth rate
• Case fatality
• Compensation law of mortality
• Demography
• Egalitarian mortality
• Gompertz-Makeham law of mortality
• Life expectancy
• List of causes of death by rate
• List of countries by death rate
• Maximum life span
• Micromort
• Morbidity
• Mortality
• Mortality displacement

Notes[link]

References[link]

• Crude death rate (per 1,000 population) based on World Population Prospects The 2008 Revision, United Nations. Retrieved 22 June 2010
• Rank Order - Death rate in CIA World Factbook
• Mortality in The Medical Dictionary, Medterms. Retrieved 22 June 2010
• "WISQARS Leading Causes of Death Reports, 1999 - 2007", US Centers for Disease Control Retrieved 22 June 2010
• Edmond Halley, An Estimate of the Degrees of the Mortality of Mankind (1693)

External links[link]

Wikimedia Commons has media related to: Birth and death rates

• DeathRiskRankings: Calculates risk of dying in the next year using MicroMorts and displays risk rankings for up to 66 causes of death
• Data regarding death rates by age and cause in the United States (from Data360)
• Complex Emergency Database (CE-DAT): Mortality data from conflict-affected populations
• Human Mortality Database: Historic mortality data from developed nations
• Google - public data: Mortality in the U.S.