Public Health (1991), 1(15, 145 151
© The Societyof Public Health, 1991
A Characteristic Change in Infant M o r t a l i t y Rate Decrease in Japan Y. Nakamura, M. Nagai and H. Yanagawa Department of Public Health, Jichi Medical School, Yakushl)i 3311- 1, Minamikawachi-machL Tochigi-ken, 329-04 Japan
Changes in infant mortality rate (IM) in Japan were observed over a 41-year period, since the end of the Second World War (1947-1987). Both neonatal mortality rate (NM) and infant mortality rate excluding neonatal deaths (IEN) were measured. It was observed that IM had considerably decreased during the observation period. A decrease of IEN contributed greatly to this fall till the 1960s and less so since the 1970s. The slope of the decrease of NM became steeper after entering the 1980s compared with that of IEN, and this contributed to the decrease of IM in this period. In order to analyse this phenomenon, detailed observations were made of the causes of death. On studying three of the major causes of infant deaths in Japan (congenital anomalies, birth trauma and perinatal asphyxia, and injuries and poisoning) it was found that there was only a small annual difference in the number of deaths due to congenital anomalies compared with the much greater difference seen with the other two causes; therefore, improvement of mortality rate by congenital anomalies seemed difficult because the efficacy of improvement of medical treatment and care are already approaching their limits. For a further reduction of IM in the future, improvement of perinatal care and prevention of injuries are considered to be essential.
Introduction The 1987 infant mortality rate in Japan was 5.0 per 1,000 live births. This is one o f the lowest rates in the world; ~ and it has been falling steadily since the Second World W a r ? By an analysis o f Japanese vital statistics data, it was observed that the present IM has some different characteristics from the patterns shown in the 1950s and 60s. This difference has been observed since the mid-1970s, when the infant mortality rate decreased to as low as 10.0 per 1,000 live births.
Methods In this study, vital statistics of Japan from 1947 to 1987 (the most recent year o f available data) were analysed. (The vital statistics of 1947 are the earliest available in Japan after World War II.) The yearly trends of the IM, the neonatal mortality rate (NM) and the infant mortality rate excluding neonatal deaths (IEN), (i.e. I M less NM) were compared. For an analysis of the causes o f death, data from the years 1979 to. 1987 were used, since the 1975 revision of the International Classification o f Diseases (ICD-9) has been applied in Japan since 1979. Because the causes of death were classified differently before 1979, especially in perinatal deaths, an analysis o f the causes o f death is impossible. Correspondence: Y. Nakamura
146
Y. Nakamura et al. Results
Figure 1 shows the changes of IM, N M and I E N over the 41-year-period from 1947 to 1987. Just after the war I M was a b o u t 50 per 1,000 live births, but this fell steadily thereafter to 40 in 1958, 30 in 1961, 20 in 1965, to below 10 in 1976 and to 5.0 in 1987. Just after the war N M was higher than 20 per 1,000 live births, but fell below 20 by 1958 and below 10 by 1967, to 2.9 in 1987. The drop in N M was slower in the 1940s and 1950s c o m p a r e d with IM; however, since around 1960 both curves have been nearly parallel. Since the beginning o f the 1980s, the fall in N M was slightly faster than that in IM. I E N was higher than N M until 1951. Thereafter, it fell in a steeper curve than N M , reversing the relationship in 1952, and the gap has widened since then. However, in the mid-1970s the fall in I E N slowed somewhat, and since the 1980s the decrease has been exceedingly small when c o m p a r e d with I M or N M . In addition, all o f these curves show a linear decline, except for one disturbance in 1965-1967. The n u m b e r o f live births in 1966 was lower than those in the preceding and the following years (number of live births in 1965 = 1,824 thousand, in 1966 = 1,361 thousand and in 1967 = 1,936 thousand). This is due to a superstition in J a p a n (Hinoeuma), i.e. some people in J a p a n believe that girls born in this year, which is once in 60 years, will become unfortunate in the future. Figure 2 shows the changes of N M in relation to total IM. In the 1940s and 50s, the
100 80
1 : Infant mortality rate (IM) 2 : Neonatal mortality rate (NM) 3 : Infant mortality rate excluding neonatal deaths (IEN)
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Figure 1 Yearly changes of infant mortality rate (IM), neonatal mortality rate (NM), and infant mortality rate excluding neonatal deaths (IEN) in Japan (1947 1987)
Infant Mortality & Japan
147
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Yearly change of proportion of neonatal deaths in infant deaths in Japan (1947-1987)
proportion of neonatal deaths to infant deaths rose steeply, because the fall in N M was slower in comparison to the fall in IEN. The fall of N M became faster in the 1960s, and, as a result, the increase of the proportion was moderated. After entering the 1970s, it became even more moderated, with a peak o f 68.8% in 1977, but declined further to 58.6% in 1987. An observation of the causes o f death was carried out in regard to the three m a j o r causes of infant death in Japan: congenital anomalies (740-759 in ICD-9), birth t r a u m a and perinatal asphyxia (767 770 in ICD-9) and injuries and poisoning (80(~999 in ICD-9). Figure 3 compares IM, N M and I E N for the three major causes of death. A relatively small reduction of deaths due to congential anomalies occurred in IM, N M and IEN. Deaths due to birth trauma and perinatal asphyxia have been decreasing in IM and N M , in contrast to the increase in IEN, so that by 1985 IM deaths due to congenital anomalies surpassed the deaths due to birth trauma and perinatal asphyxia. Deaths due to injuries and poisoning have decreased in IM, N M and IEN. Proportions of N M in IM were different a m o n g the three major causes of death. The proportion of N M due to congenital anomalies was 53%, whereas it was 95% for birth t r a u m a and perinatal asphyxia, and 16% for injuries and poisoning. Detailed trends of the causes of deaths are shown in Tables I and II. These tables give a comparison o f the ratio of the causes of death between the first and last three years o f observation (from 1979 to 1981 and from 1985 to 1987). As shown in Table I, the I M of all causes of death in the first three years was 7.51 and that in the last three years was 5.25, a 70% reduction. I E N rate dropped to only 82% in spite of a 64% drop in N M . Looking at the causes of death separately, reduction of congenital anomalies, when c o m p a r e d with the reduction o f all causes of death, is rather small for IM and N M , but is similar to IEN. A marked reduction is found in perinatal diseases as a cause of death in I M and NM. However, the role of these causes in I E N has been increasing in recent years. In injuries and poisoning, it is atmqst the same as the reduction of all causes o f death in N M
148
Y. N a k a m u r a
et al.
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Yearly changes of IM, NM and IEN for three major causes in Japan (1979-1987)
and IEN. Deaths due to heart diseases show an increase in IM, NM and IEN (especially in NM). More detailed observations of disease entities are shown in Table II. Sepsis and congenital anomalies (the circulatory systems excluding the heart) are increasing. Also, a detailed differentiation of birth trauma and perinatal asphyxia in Table II shows that birth trauma of the central nervous system and perinatal asphyxia decreased as a cause of death in NM, but rose in IEN. It is shown that bronchitis and pneumonia, congenital anomalies of the nervous system, congenital anomalies of the gastrointestinal system, and delivery of a premature baby had decreased more than any other causes in IM, NM and IEN. In injuries and poisoning, the trend of decrease in accidental mechanical suffocation was larger than that for inhalation and ingestion. Discussion
The fall of IM in Japan after World War II is thought to be due to improvement of medical equipment and hygiene, and to the economic growth that supports these changes. It is a point of great interest as to what degree IM may drop, and what is the lowest possible level from a biological point of view. The decreasing tendency of IM in Japan continues up to the present day. However, there have been changes in what constitutes IM over the past 10 years. In other words, the proportion of NM to total IM continued to increase after the Second World War but began to decrease in the last decade. This phenomenon was mainly ascribed
Infant Mortality in Japan
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to the fact that the rate of fall of IM became slow. In the 1950s and 60s, rather than an improvement in N M , the drop in the I E N greatly contributed to the decrease o f IM. In the 1970s, I E N nearly reached the lowest limit, and the fall in N M became slightly larger, so that IM (which is the total of N M and IEN) has decreased constantly. In an analysis o f the causes of death, a marked d r o p in perinatal diseases, including birth t r a u m a and perinatal asphyxia, birth trauma o f the central nervous system, perinatal asphyxia and premature babies has been seen, especially in the neonatal period. These phenomena are thought to be due to substantial improvements of medical treatment in neonatal intensive care units, and to care in the perinatal period. These effects can also be conjectured from the drop in perinatal mortality rate in Japan. Moreover, because of the improvement of perinatal care, a number of newborns who formerly would not have survived may now survive to live for more than 28 days and die later. These deaths m a y contribute to making the curve o f yearly change in I E N near horizontal in recent years. The leading cause of infant mortality in J a p a n at the present time is congenital anomalies, and this shows a slower decrease within I M and N M when c o m p a r e d with other causes of death. This suggests that, concerning congenital anomalies, the efficacy o f improvement of medical treatment and care are already approaching their limits. In spite of a decrease of IM due to injuries and poisoning, the trend is not so large as that for all causes. There were 528 infant deaths in J a p a n in 1987, and 347 (or 65.7%) were caused by submersion, suffocation and foreign bodies (E910-E915 in ICD-9). 3 M a n y of these cases were thought to have occurred in the h o m e out of sight o f the parents or those in charge of the infant. The number of infant deaths by homicide and injuries purposely inflicted by other persons (E96(~E969 in ICD-9) was also large in J a p a n (77 cases or 14.6% of infant deaths in 1987). 3 Included in this figure are newborn infants, the product of unplanned pregnancies, who are killed by their parents. This fact suggests that sex education, especially in schools, is necessary to help prevent these unfortunate deaths. In order to decrease IM even further in Japan, it would be necessary to expand perinatal care even more and to take measures to prevent injuries to infants, especially infants o f more than 28 days of age. Parental education, including sex education, is thought to form the nucleus of this latter scheme.
References
1. World Health Organization. (1988). Worm Health Statistics Annual 1988. Geneva: WHO. pp. 78 79. 2. Statistics and Information Department, Minister's Secretariat, Ministry of Health and Welfare. (1989). 1989 Health and Welfare Statistics in Japan. Tokyo: Health and Welfare Statistics Association. p. 51. 3. Statistics and Information Department, Minister's Secretariat, Ministry of Health and Welfare. (1989). Vital Statistics 1987 in Japan, Vol. 3. Tokyo: Health and Welfare Statistics Association, pp. 200-231.
© The Societyof Public Health, 1991
A Characteristic Change in Infant M o r t a l i t y Rate Decrease in Japan Y. Nakamura, M. Nagai and H. Yanagawa Department of Public Health, Jichi Medical School, Yakushl)i 3311- 1, Minamikawachi-machL Tochigi-ken, 329-04 Japan
Changes in infant mortality rate (IM) in Japan were observed over a 41-year period, since the end of the Second World War (1947-1987). Both neonatal mortality rate (NM) and infant mortality rate excluding neonatal deaths (IEN) were measured. It was observed that IM had considerably decreased during the observation period. A decrease of IEN contributed greatly to this fall till the 1960s and less so since the 1970s. The slope of the decrease of NM became steeper after entering the 1980s compared with that of IEN, and this contributed to the decrease of IM in this period. In order to analyse this phenomenon, detailed observations were made of the causes of death. On studying three of the major causes of infant deaths in Japan (congenital anomalies, birth trauma and perinatal asphyxia, and injuries and poisoning) it was found that there was only a small annual difference in the number of deaths due to congenital anomalies compared with the much greater difference seen with the other two causes; therefore, improvement of mortality rate by congenital anomalies seemed difficult because the efficacy of improvement of medical treatment and care are already approaching their limits. For a further reduction of IM in the future, improvement of perinatal care and prevention of injuries are considered to be essential.
Introduction The 1987 infant mortality rate in Japan was 5.0 per 1,000 live births. This is one o f the lowest rates in the world; ~ and it has been falling steadily since the Second World W a r ? By an analysis o f Japanese vital statistics data, it was observed that the present IM has some different characteristics from the patterns shown in the 1950s and 60s. This difference has been observed since the mid-1970s, when the infant mortality rate decreased to as low as 10.0 per 1,000 live births.
Methods In this study, vital statistics of Japan from 1947 to 1987 (the most recent year o f available data) were analysed. (The vital statistics of 1947 are the earliest available in Japan after World War II.) The yearly trends of the IM, the neonatal mortality rate (NM) and the infant mortality rate excluding neonatal deaths (IEN), (i.e. I M less NM) were compared. For an analysis of the causes o f death, data from the years 1979 to. 1987 were used, since the 1975 revision of the International Classification o f Diseases (ICD-9) has been applied in Japan since 1979. Because the causes of death were classified differently before 1979, especially in perinatal deaths, an analysis o f the causes o f death is impossible. Correspondence: Y. Nakamura
146
Y. Nakamura et al. Results
Figure 1 shows the changes of IM, N M and I E N over the 41-year-period from 1947 to 1987. Just after the war I M was a b o u t 50 per 1,000 live births, but this fell steadily thereafter to 40 in 1958, 30 in 1961, 20 in 1965, to below 10 in 1976 and to 5.0 in 1987. Just after the war N M was higher than 20 per 1,000 live births, but fell below 20 by 1958 and below 10 by 1967, to 2.9 in 1987. The drop in N M was slower in the 1940s and 1950s c o m p a r e d with IM; however, since around 1960 both curves have been nearly parallel. Since the beginning o f the 1980s, the fall in N M was slightly faster than that in IM. I E N was higher than N M until 1951. Thereafter, it fell in a steeper curve than N M , reversing the relationship in 1952, and the gap has widened since then. However, in the mid-1970s the fall in I E N slowed somewhat, and since the 1980s the decrease has been exceedingly small when c o m p a r e d with I M or N M . In addition, all o f these curves show a linear decline, except for one disturbance in 1965-1967. The n u m b e r o f live births in 1966 was lower than those in the preceding and the following years (number of live births in 1965 = 1,824 thousand, in 1966 = 1,361 thousand and in 1967 = 1,936 thousand). This is due to a superstition in J a p a n (Hinoeuma), i.e. some people in J a p a n believe that girls born in this year, which is once in 60 years, will become unfortunate in the future. Figure 2 shows the changes of N M in relation to total IM. In the 1940s and 50s, the
100 80
1 : Infant mortality rate (IM) 2 : Neonatal mortality rate (NM) 3 : Infant mortality rate excluding neonatal deaths (IEN)
~ . " ~
40
.~
~
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2o
10
1
4 'x__ 2
,,,i . . 1950
. . . . . .
~
-
1960
~
. . . . J~1970 (Year)
~2
1980
Figure 1 Yearly changes of infant mortality rate (IM), neonatal mortality rate (NM), and infant mortality rate excluding neonatal deaths (IEN) in Japan (1947 1987)
Infant Mortality & Japan
147
70
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1960
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1970
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Year
Figure 2
Yearly change of proportion of neonatal deaths in infant deaths in Japan (1947-1987)
proportion of neonatal deaths to infant deaths rose steeply, because the fall in N M was slower in comparison to the fall in IEN. The fall of N M became faster in the 1960s, and, as a result, the increase of the proportion was moderated. After entering the 1970s, it became even more moderated, with a peak o f 68.8% in 1977, but declined further to 58.6% in 1987. An observation of the causes o f death was carried out in regard to the three m a j o r causes of infant death in Japan: congenital anomalies (740-759 in ICD-9), birth t r a u m a and perinatal asphyxia (767 770 in ICD-9) and injuries and poisoning (80(~999 in ICD-9). Figure 3 compares IM, N M and I E N for the three major causes of death. A relatively small reduction of deaths due to congential anomalies occurred in IM, N M and IEN. Deaths due to birth trauma and perinatal asphyxia have been decreasing in IM and N M , in contrast to the increase in IEN, so that by 1985 IM deaths due to congenital anomalies surpassed the deaths due to birth trauma and perinatal asphyxia. Deaths due to injuries and poisoning have decreased in IM, N M and IEN. Proportions of N M in IM were different a m o n g the three major causes of death. The proportion of N M due to congenital anomalies was 53%, whereas it was 95% for birth t r a u m a and perinatal asphyxia, and 16% for injuries and poisoning. Detailed trends of the causes of deaths are shown in Tables I and II. These tables give a comparison o f the ratio of the causes of death between the first and last three years o f observation (from 1979 to 1981 and from 1985 to 1987). As shown in Table I, the I M of all causes of death in the first three years was 7.51 and that in the last three years was 5.25, a 70% reduction. I E N rate dropped to only 82% in spite of a 64% drop in N M . Looking at the causes of death separately, reduction of congenital anomalies, when c o m p a r e d with the reduction o f all causes of death, is rather small for IM and N M , but is similar to IEN. A marked reduction is found in perinatal diseases as a cause of death in I M and NM. However, the role of these causes in I E N has been increasing in recent years. In injuries and poisoning, it is atmqst the same as the reduction of all causes o f death in N M
148
Y. N a k a m u r a
et al.
3.0 ii
II
2.0
"5 1.0
1-3 Congenital anomalies 1 :IM( ) 2:NM(. ) 3 :IEN (--)
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7:( .... ) 8 : NM ( .... ) 9 :IEN (..... )
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87
Yearly changes of IM, NM and IEN for three major causes in Japan (1979-1987)
and IEN. Deaths due to heart diseases show an increase in IM, NM and IEN (especially in NM). More detailed observations of disease entities are shown in Table II. Sepsis and congenital anomalies (the circulatory systems excluding the heart) are increasing. Also, a detailed differentiation of birth trauma and perinatal asphyxia in Table II shows that birth trauma of the central nervous system and perinatal asphyxia decreased as a cause of death in NM, but rose in IEN. It is shown that bronchitis and pneumonia, congenital anomalies of the nervous system, congenital anomalies of the gastrointestinal system, and delivery of a premature baby had decreased more than any other causes in IM, NM and IEN. In injuries and poisoning, the trend of decrease in accidental mechanical suffocation was larger than that for inhalation and ingestion. Discussion
The fall of IM in Japan after World War II is thought to be due to improvement of medical equipment and hygiene, and to the economic growth that supports these changes. It is a point of great interest as to what degree IM may drop, and what is the lowest possible level from a biological point of view. The decreasing tendency of IM in Japan continues up to the present day. However, there have been changes in what constitutes IM over the past 10 years. In other words, the proportion of NM to total IM continued to increase after the Second World War but began to decrease in the last decade. This phenomenon was mainly ascribed
Infant Mortality in Japan
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to the fact that the rate of fall of IM became slow. In the 1950s and 60s, rather than an improvement in N M , the drop in the I E N greatly contributed to the decrease o f IM. In the 1970s, I E N nearly reached the lowest limit, and the fall in N M became slightly larger, so that IM (which is the total of N M and IEN) has decreased constantly. In an analysis o f the causes of death, a marked d r o p in perinatal diseases, including birth t r a u m a and perinatal asphyxia, birth trauma o f the central nervous system, perinatal asphyxia and premature babies has been seen, especially in the neonatal period. These phenomena are thought to be due to substantial improvements of medical treatment in neonatal intensive care units, and to care in the perinatal period. These effects can also be conjectured from the drop in perinatal mortality rate in Japan. Moreover, because of the improvement of perinatal care, a number of newborns who formerly would not have survived may now survive to live for more than 28 days and die later. These deaths m a y contribute to making the curve o f yearly change in I E N near horizontal in recent years. The leading cause of infant mortality in J a p a n at the present time is congenital anomalies, and this shows a slower decrease within I M and N M when c o m p a r e d with other causes of death. This suggests that, concerning congenital anomalies, the efficacy o f improvement of medical treatment and care are already approaching their limits. In spite of a decrease of IM due to injuries and poisoning, the trend is not so large as that for all causes. There were 528 infant deaths in J a p a n in 1987, and 347 (or 65.7%) were caused by submersion, suffocation and foreign bodies (E910-E915 in ICD-9). 3 M a n y of these cases were thought to have occurred in the h o m e out of sight o f the parents or those in charge of the infant. The number of infant deaths by homicide and injuries purposely inflicted by other persons (E96(~E969 in ICD-9) was also large in J a p a n (77 cases or 14.6% of infant deaths in 1987). 3 Included in this figure are newborn infants, the product of unplanned pregnancies, who are killed by their parents. This fact suggests that sex education, especially in schools, is necessary to help prevent these unfortunate deaths. In order to decrease IM even further in Japan, it would be necessary to expand perinatal care even more and to take measures to prevent injuries to infants, especially infants o f more than 28 days of age. Parental education, including sex education, is thought to form the nucleus of this latter scheme.
References
1. World Health Organization. (1988). Worm Health Statistics Annual 1988. Geneva: WHO. pp. 78 79. 2. Statistics and Information Department, Minister's Secretariat, Ministry of Health and Welfare. (1989). 1989 Health and Welfare Statistics in Japan. Tokyo: Health and Welfare Statistics Association. p. 51. 3. Statistics and Information Department, Minister's Secretariat, Ministry of Health and Welfare. (1989). Vital Statistics 1987 in Japan, Vol. 3. Tokyo: Health and Welfare Statistics Association, pp. 200-231.
