Mortality and Morbidity in Children - Ministry of Health

Chapter 2
Mortality and Morbidity in
Children
Key points
• The New Zealand mortality rate for children aged 0–4 years currently ranks 15th out of 21
OECD countries. This is a fall from a position of sixth out of 21 countries in 1960. Between 1960
and 1995, New Zealand experienced the fifth smallest decline in the under-five-year-old mortality
rate of these 21 OECD countries.
• In New Zealand, 620 children aged 0–14 died in 1994, an age-specific rate of 76 deaths per
100,000 population.
• The death rate for Mäori children aged 0–14 years is consistently higher than for non-Mäori
(83 percent higher in 1994).
• Infants (aged under one year) are considerably more at risk of death than are older children.
Two-thirds of childhood deaths each year are infants under one year of age. In 1994, the infant
death rate was 16 times higher than the death rate for 1–4-year-olds and 35 times the death rate
for 5–14-year-olds.
• The major causes of infant death are sudden infant death syndrome (SIDS), congenital anomalies
and perinatal conditions. These three causes accounted for 84 percent of all infant deaths in
1992–94.
• Injury and poisoning is the leading cause of death for children aged 1–14 years. Each year this
cause accounts for close to half of all deaths for children in this age group.
• Mäori record higher death rates than non-Mäori for most of the major causes of death in children.
In 1994, particularly high disparities between Mäori and non-Mäori were apparent for SIDS,
respiratory conditions, and injuries and poisonings.
• Childhood death rates are declining over time. Between 1980 and 1994 there was an average
annual decline of 2.7 percent in the overall death rate of 0–14-year-olds.
• There was a total of 111,571 hospitalisations (excluding newborns) for 0–14-year-olds in 1995.
Just over a third (35 percent) of these hospitalisations were for infants (aged 0–12 months).
• Hospitalisation rates decrease markedly after the first year of life, with 1–4-year-olds hospitalised
at one-fifth the rate of infants.
• Within each age group, and for most of the major causes of hospitalisation, Mäori children are
hospitalised at higher rates than non-Mäori children.
• Children are being hospitalised at an increasing rate. Over the period 1988-95, there was an
average annual increase of 5 percent in the hospitalisation rate of 0–14-year-olds.
Mortality and Morbidity in Children
21

Mortality
Childhood deaths totalled 620 in 1994. This represents an age-specific rate of 76 deaths per 100,000
children aged 0–14 years (Table 2.1).
More boys than girls die each year in New Zealand, with boys accounting for 56 percent of childhood
deaths in 1994. Mäori children are at higher risk of dying before the age of 15 years than are non-
Mäori children. In 1994, Mäori children recorded a death rate that was 83 percent higher than non-
Mäori children (125 and 68 per 100,000 children aged 0–14 years for Mäori and non-Mäori
respectively)
Table 2.1: Deaths from all causes, by sex and ethnicity, 0–14-year-olds, 1994
Number Percentage Rate*
Total 620 76
Male 349 56% 83
Female 271 44% 68
Relative risk for males 1.22
Mäori 134 22% 125
Non-Mäori 486 78% 68
Relative risk for Mäori 1.83
*Age-specific rate per 100,000 population.
Source of data:
Ministry of Health 1998.
Infants under one year are at much greater risk of dying than are older children (Table 2.2). In
1994, two-thirds of all childhood deaths were infants (a rate of seven infant deaths per 1000
livebirths).
The risk of dying in childhood decreases rapidly after the first year. In 1994, the death rate for
children aged 1–4 years was 44 per 100,000, a rate 16 times lower than for infants, although still
twice the rate recorded in the 5–9 and 10–14 year age groups.
The disparity between Mäori and non-Mäori death rates in children is apparent in each of the age
groups, shown in table 2.2.
22 Our Children’s Health

Table 2.2: Deaths from all causes, by age group, 0–14-year-olds, 1994
Total Mäori Non-Mäori
Age group Number Rate* Number Rate* Number Rate*

Figure 2.2: Major causes of death of 1–4-year-olds, 1992–94
Other
causes 19%
Nervous system
disorders 8%
Injury and
poisoning 46%
Cancer 11%
Congenital
anomalies 16%
Source of data:
Ministry of Health 1998.
Injury and poisoning is also the most common cause of death in the 5–9 and 10–14 year age groups,
accounting for nearly half of all deaths each year (47 percent in the 5–9 year age group and 48
percent in the 10–14 year age group in 1992-94) (Figures 2.3 and 2.4).
Cancer is also a common cause of death for children in the 5–9 and 10–14 year age groups,
accounting for 21 percent and 14 percent of deaths respectively in these age groups in 1992–94.
Figure 2.3: Major causes of death of 5–9-year-olds, 1992–94
Other
causes 13%
Nervous system
disorders 8%
Cancer 21%
Injury and
poisoning 47%
Congenital
anomalies 11%
Source of data:
Ministry of Health 1998.
24 Our Children’s Health

Figure 2.4: Major causes of death of 10–14-year-olds, 1992–94
Other
causes 19%
Nervous system
disorders 12%
Injury and
poisoning 48%
Cancer 14%
Source of data:
Ministry of Health 1998.
Congenital
anomalies 7%
Mäori children are at greater risk of death than non-Mäori children for most of the major causes
(Table 2.3). Between 1992 and 1994, the greatest disparity in death rates between Mäori and non-
Mäori children was recorded for SIDS and respiratory conditions. For SIDS, Mäori children recorded
a rate 4.5 times the non-Mäori rate, while for respiratory conditions the Mäori death rate was 2.7
times that for non-Mäori children. For road traffic injuries and for other injuries and poisonings,
Mäori children recorded death rates 1.5 times higher than non-Mäori children. Compared to non-
Mäori children, death rates for Mäori were similar or lower for congenital anomalies, perinatal
conditions, cancer, nervous system disorders, and infectious diseases.
Table 2.3: Major causes of death, by ethnicity, 0–14-year-olds, 1992–94
Mäori Non-Mäori Relative risk
for Mäori
Number Rate* Number Rate*
Congenital anomalies 50 15.5 392 18.7 0.8
SIDS** 144 6.7 231 1.5 4.5
Perinatal conditions** 50 2.3 301 2.0 1.2
Injury and poisoning 43 13.4 182 8.7 1.5
(other than road traffic injuries)
Road traffic injuries 26 8.1 113 5.4 1.5
Cancer 12 3.7 92 4.4 0.8
Nervous system disorders 7 2.2 83 4.0 0.6
Respiratory conditions 21 6.5 51 2.4 2.7
Infectious diseases 7 2.2 35 1.7 1.3
All other causes 13 4.0 84 4.0 1.0
All causes 373 115.9 1564 74.7 1.6
* Rate per 100,000 population.
** Infant deaths only, rates per 1000 livebirths.
Source of data:
Ministry of Health 1998.
Mortality and Morbidity in Children
25

Changes over time
Childhood death rates are continuing to decline in New Zealand. Between 1980 and 1994, the
death rate for the 0–14 year age group decreased from 115 to 76 per 100,000, an annual average
decrease of 2.9 percent (Figure 2.5).
This decrease was not evenly shared between Mäori and non-Mäori. For Mäori children, an annual
average decrease of 1.7 percent was recorded between 1980 and 1994, compared to an annual
average decrease of 3.3 percent for non-Mäori. Overall, during this 15–year period the disparity
between Mäori and non-Mäori rates of childhood deaths increased.
Figure 2.5: Deaths from all causes, by ethnicity, 0–14-year-olds, 1980–94
Rate per 100,000 population
160
140
120
100
80
60
40
20
0
1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994
Year
Source of data:
Ministry of Health 1998.
Total Maori Non-Maori
Decreases in all-cause death rates have been recorded for all age groups under 15 years between
1980 and 1994 (Table 2.4). For each age group, an annual average decrease of between 2.7 percent
and 3.3 percent in the overall death rate was recorded during this time.
Table 2.4: Reduction in numbers and rates of death, by age group, 0–14-year-olds, 1980–94
1980 1994 Total Annual
reduction reduction
No. *Rate No. *Rate

Morbidity
This section summarises recent hospitalisation data from the National Minimum Dataset,
maintained by the New Zealand Health Information Service. The data presented here are based
on numbers of hospitalisation events, not numbers of unique individuals hospitalised. Both
daypatient and inpatient hospitalisations are included. One unique individual may be represented
in the data several times if they were hospitalised as a daypatient or inpatient more than once.
In 1995, hospitalisations totalled 111,571 for New Zealand 0–14-year-olds (Table 2.5).
Table 2.5: Hospitalisations from all causes, by sex and ethnicity, 0–14-year-olds, 1995
Number Percentage Rate*
Total 111,571 13,450
Male 63,416 57% 14,890
Female 48,155 43% 11,920
Relative risk for males 1.25
Mäori 24,259 22% 22,660
Non- Mäori 87,312 78% 12,080
Relative risk for Mäori 1.88
* Age-specific rate per 100,000 population.
Source of data:
Ministry of Health 1998.
Note:
Sums of males and females, and Maori and non-Maori may be less than totals, as a small number of patients for
whom sex and ethnicity were not recorded are included in totals.
In 1995, as is usually the case, a greater proportion of boys (57 percent) than girls (43 percent) were
hospitalised. In addition, Mäori children were hospitalised at nearly twice the rate of non-Mäori
children.
Hospitalisation rates decrease with increasing age during childhood (Table 2.6). Infants less than
one year old record the highest rate of hospitalisation. In 1995, infants were hospitalised at almost
10 times the rate of any other childhood age group and accounted for 35 percent of all childhood
hospitalisation events.
Those aged 10–14 years are the least likely childhood group to be hospitalised. In 1995, 10–14-
year-olds were hospitalised at one twentieth of the infant hospitalisation rate and at half of the
1–4-year-old hospitalisation rate.
Mortality and Morbidity in Children
27

Table 2.6: Hospitalisations from all causes, by age group and ethnicity, 0–14-year-olds, 1995

For children aged 1–4 years, respiratory conditions are the most common reason for hospitalisation.
These conditions accounted for 26 percent of hospitalisations in this age group in 1995 (Figure
2.7). Injury and poisoning was the second most common reason for hospitalisation.
Figure 2.7: Major causes of hospitalisation of 1–4-year-olds, 1995
Other
causes 24%
Respiratory
conditions 26%
Digestive system
disorders 9%
Infectious and
parasitic disorders
9%
Source of data:
Ministry of Health 1998.
Nervous system
disorders 15%
Injury and
poisoning 17%
From age five years and older, more children are hospitalised due to an injury or poisoning than
for any other reason. In 1995, nearly one-quarter (24 percent) of hospitalisations for 5–9-year-olds
and nearly one-third (31 percent) of hospitalisations for 10–14-year-olds were due to these causes
(Figures 2.8 and 2.9).
Figure 2.8: Major causes of hospitalisation of 5–9-year-olds, 1995
Other
causes 32%
Injury and
poisoning 24%
Symptoms* 5%
Infectious and
parasitic disorders
5%
Nervous system
disorders 16%
Respiratory
conditions 18%
* Symptoms, signs, and ill-defined conditions (ICD-9 codes 780-799).
Source of data:
Ministry of Health 1998.
Mortality and Morbidity in Children
29

Figure 2.9: Major causes of hospitalisation of 10–14-year-olds, 1995
Other
causes 30%
Injury and
poisoning 31%
Symptoms 8%
Nervous system
disorders 8%
Source of data:
Ministry of Health 1998.
Digestive system
disorders 9%
Respiratory
conditions 14%
In 1995, respiratory conditions (including asthma, pneumonia, influenza, and bronchitis), were
the second most common reason for the hospitalisation of children aged 5–14 years.
Compared to non-Mäori, Mäori children have higher rates of hospitalisation for almost every
group of conditions. The largest disparities between Mäori and non-Mäori hospitalisation rates
are evident for nervous system conditions, respiratory conditions, and injuries and poisonings.
For each of these groups of causes, Mäori children are hospitalised at about twice the rate of non-
Mäori children.
Table 2.7: Major causes of hospitalisation, by ethnicity, 0–14-year-olds, 1995
Cause Total Mäori Rate* Non-Mäori Rate* Relative
No. No. No. risk for
Mäori
Respiratory conditions 20,709 5,613 5,244 15,096 2,089 2.5
Injury and poisoning 15,492 3,348 3,128 12,144 1,680 1.9
Perinatal conditions 15,907 3,107 2,903 12,800 1,771 1.6
Nervous system diseases 10,848 2,700 2,522 8,148 1,127 2.2
Digestive system disorders 8,279 1,735 1,621 6,544 906 1.8
Symptoms** 6,931 1,375 1,285 5,556 769 1.7
Infectious and parasitic
diseases 6,829 1,343 1,255 5,486 759 1.7
Congenital anomalies 5,712 1,113 1,040 4,599 636 1.6
Genitourinary disorders 3,019 459 429 2,560 354 1.2
Musculoskeletal diseases 2,180 401 375 1,779 246 1.5
All causes 111,571 24,259 22,660 87,312 12,080 1.9
* Age-specific rate per 100,000 population.
** Symptoms, signs, and ill-defined conditions (ICD-9 codes 780-799).
Source of data:
Ministry of Health 1998.
Note:
Columns do not sum to totals because totals include causes other than the ones shown.
30 Our Children’s Health

Changes over time
Changes in hospitalisation rates may be due to a number of factors including:
• changes in hospital admission policy
• changes in hospital recording systems (for example, revised definitions of daypatients and
outpatients)
• changes in the case-mix of patients presenting for treatment (for example, more severe cases)
• changes in the rate of disease in the community.
Between 1988 and 1995, an increasing number of children aged 0–14 years were hospitalised. In
1988, there were 77,817 childhood hospitalisations, rising to 111,571 in 1995 (Table 2.8). This
translates to an average annual increase in the childhood hospitalisation rate of 5 percent. The
infant hospitalisation rate increased the most, with an overall increase of 40 percent recorded
between 1988 and 1995.
Table 2.8: Increase in hospitalisation numbers and rates for 0–14-year-olds, 1988–95
1988 1995 Total Annual
increase increase
AGE No. Rate* No. Rate*

Figure 2.10: Total hospitalisation rates, by ethnicity, 0–14-year-olds, 1988–95
Rate per 100,000 population
25,000
20,000
15,000
10,000
5,000
0
1988 1989
1990 1991 1992 1993 1994
Year
Total Maori Non-Maori
1995
Source of data:
Ministry of Health 1998.
International comparisons
Under-five mortality
The under-five mortality rate is a well-accepted indicator of a country’s overall health status. New
Zealand ranks 15th out of the 21 OECD countries that have reliable child mortality data available
for comparison (Figure 2.11). Sweden reported the lowest under-five mortality rate in 1995, with
the United Kingdom and Australia ranked fourth and 10th respectively (UNICEF 1995).
Figure 2.11: Under–5-year-old mortality rates, OECD countries
Rate per 100,000 population
12
10
8
6
4
2
0
Portugal
Greece
Belgium
USA
Spain
France
New Zealand
Italy
Canada
Netherlands
Norway
Australia
Ireland
Germany
Austria
Denmark
Switzerland
UK
Japan
Finland
Sweden
Source of data:
UNICEF 1995.
32 Our Children’s Health

New Zealand’s international ranking in under-five mortality has worsened over the last 25 years.
In 1960, New Zealand ranked sixth out of 21 OECD countries with available data for this measure.
Between 1960 and 1995, New Zealand experienced the fifth lowest rate of change in under-five
mortality out of these 21 OECD countries (Figure 2.12).
Figure 2.12: Percentage fall in under–5-year-old mortality rates, OECD countries, 1960–95
Percentage
100
90
80
70
60
50
40
30
20
10
0
Portugal
Japan
Greece
Source of data:
UNICEF 1995.
Spain
Italy
Austria
Germany
Finland
Ireland
Canada
Sweden
Switzerland
UK
France
Denmark
Belgium
New Zealand
USA
Australia
Norway
Netherlands
References
Ministry of Health. 1998. Unpublished data from the National Minimum Dataset, New Zealand
Health Information Service. Wellington: Ministry of Health.
UNICEF. 1995. The State of the World’s Children. Oxford: Oxford University Press.
Mortality and Morbidity in Children
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