Changing age patterns of mortality and cause of death

It is evident from the analysis of the results in Section 8.1 that between the late 1950s and early 1980s there was a substantial reduction in child deaths at all ages. The improvement in survival chances was greatest in late childhood (ages three and four), and smallest in the first year, particularly the first month of life.19 These differential changes indicate a gradual transition in the age pattern of mortality.

The changing age patterns of mortality can be used to draw broad inferences about the causes of mortality decline. For example, in their analysis of trends in child mortality in Jordan during the 25 years leading up to 1976, Blacker et al. (1983) established that mortality at ages one to four had fallen even more sharply than infant mortality. Noting that this same trend has been observed elsewhere the writers state, „Very simply, it seems that early childhood rather than infant mortality is more affected by a reduction in the incidence of the infectious diseases which is usually among the first targets of government health programmes.‟ (Blacker et al., 1983, p.18). Also, Sullivan (1973) has demonstrated that in countries where gastroenteritis is a leading cause of death, a South mortality pattern with relatively high child compared to infant mortality is most likely to prevail because children are the most susceptible to diarrhoeal diseases.

Table 8.5 Mortality rates for children born in 1955-65 and 1975-85 and corresponding Coale and Demeny model life tables

Age Rate Level of mortality

19

From Table 8.3, rough estimates of the decreases in the probabilities of dying between 1955-60 and 1975-80 are 88, 83 and 73 per cent at ages two to four years, one year and 1-11 months respectively. The figures indicate a 34 per cent reduction in the neonatal mortality rate over the same period.

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(x) (1qx) West North East South

Female Male Female Male Female Male Female Male

1955-65 0 0.1301 12.16 13.67 10.98 12.60 14.13 15.67 13.09 14.49 1 0.0547 11.54 12.72 10.52 11.86 12.97 14.33 13.03 13.89 2 0.0282 11.25 12.34 10.64 11.85 12.49 13.76 12.95 13.68 3 0.0116 11.36 12.37 11.11 12.20 12.48 13.67 13.06 13.74 4 0.0029 11.64 12.57 11.64 12.63 12.08 13.80 13.26 13.91 1975-85 0 0.0472 19.33 20.47 19.18 20.26 20.47 21.34 22.33 22.94 1 0.0057 19.52 20.46 19.54 20.39 20.41 21.20 22.31 22.80 2 0.0030 19.57 20.46 19.78 20.57 20.36 21.13 22.29 22.75 3 0.0018 19.61 20.48 19.97 20.72 20.35 21.10 22.27 22.73 4 0.0007 19.69 20.55 20.15 20.87 20.38 21.13 22.29 22.75

Sources: Maternity histories and Coale and Demeny (1983).

In Table 8.5 the mortality rates for children born in two ten-year periods, 1955-65 and 1975-85 are compared with the West, North, East and South families of the Coale and Demeny (1983) model life tables. These groups of models represent the four broad patterns of mortality which have been observed in populations for which reliable age at death statistics are available. For the earliest period the Gaza mortality rates for each single year of age correspond very closely to the South female level 13 model life table. The South models incorporate higher mortality at ages one to four than both the West models for high overall levels of mortality (infant mortality above 95 per thousand), and the East models. The level of mortality at ages three and four in the study population was lower than that in the North family of model life tables.

By 1975-85, the pattern of mortality in the study communities closely resembled the West model for males although the number of deaths at age four was slightly lower than in this model. Although the figures in Table 8.5 show that the 1975-85 Gaza pattern is clearly different from the North family, it resembles both the East and the South models for females. The West model represents a sort of „average‟ mortality pattern (Newell, 1988, p.138). For this reason (and also because Israeli mortality data are among those used to derive the West family of life tables), the West model is employed for the indirectly estimated measures of childhood mortality that are presented in Section 8.1.

This comparison of the survey results with the four different patterns of mortality confirms that over the period covered by the survey there was a significant shift in the pattern of mortality at young ages. The high mortality at ages one to four relative to infant mortality was gradually replaced by an increasing concentration of child deaths in the

first year of life. The changing pattern of deaths at young ages in Gaza would, it is argued, be consistent with a decrease in mortality from infectious diseases in general, and diarrhoeal-related causes in particular. Although there is no cause of death information for ash-Shati and ash-Shaja„iyya, some support for this thesis can be derived from other data sources on both infectious diseases and cause of death in Gaza and the region. Some of these data have been presented in Chapter 3. General trends only can be inferred from the recorded data because its accuracy is limited by incomplete reporting, variations in diagnoses, and differential grouping of causes.

During the period of Egyptian administration over the Gaza Strip, large numbers of deaths in Egypt were attributed to infectious diseases and the pattern of disease in Gaza was probably broadly similar. In Egypt in 1967, the cause-specific mortality rates for diarrhoea, respiratory infections and tuberculosis were 454, 160 and approximately 12 deaths per 100,000 population respectively (Omran, 1973, pp. 56 and 59). In the period 1950-65, the cause-specific infant mortality rates were gastroenteritis 68, congenital debility and malformation 34, pneumonia and bronchitis 16, measles 1, and other causes 5 deaths per thousand live births (Omran, 1973, p.61).

Tuberculosis was prevalent in the Gaza Strip and in 1956 the UNRWA-administered tuberculosis hospital in Buraij refugee camp opened a children‟s ward. However, since in 1955-65 child mortality in ash-Shati and ash-Shaja„iyya was lower than in the North model life tables which were derived from populations with a high incidence of tuberculosis, child deaths from this cause were probably relatively few in number. The number of child death from other notifiable causes in this period is also unknown. However, the Egyptian administration and UNRWA‟s mass immunizations against typhoid and enteric fever and the introduction of smallpox, polio and diphtheria-pertussis- tetanus (DPT) vaccinations in the 1950s (Israel, MH, 1986), must have contributed to the reduction in child deaths between the late 1950s and the late 1960s. In contrast, the first measles vaccination programme was initiated by UNRWA in 1966 (UNRWA, 1983) and the incidence of this disease during the 1950s and 1960s is likely to have been as least as high as in the early years of Israeli rule (Table 8.6). Numerous late infant and child deaths associated with measles presumably occurred. The reported cause of death data for Gaza refugee camp infants in 1961-64 give an indication of the high level of mortality from non-notifiable infectious diseases that prevailed during the period of Egyptian rule. As Table 8.6 Reported cases of selected infectious diseases (per 100,000 population), Gaza Strip

181 1968-69 1970-74 1975-79 1980-84 1985 Polio 15.1 10.1 5.9 0.7 0.0 Diptheria 0.0 0.0 0.4 0.0 0.0 Pertussis 31.1 8.0 3.9 20.7 71.8 Tetanus 10.5 10.6 12.9 3.1 2.1 Measles 430.6 529.4 134.1 96.3 70.8 Typhoid 15.6 10.7 1.6 3.3 2.1 Infectious hepatitis 213.1 224.3 45.8 _72.2* 100.9 Cholera 0.0 13.2 0.0 8.3 0.0

Tuberculosis N/A _42.0+ _30.2# 12.9 N/A

*

1980, 1981, 1983, 1984; + 1972-74; # 1975, 1977-79; N/A Not available. Source: Israel, MH (1986), pp. 133, 135.

Table 8.7 Selected infant mortality rates, Gaza Strip and West Bank

Age at death / cause of death Deaths per 1000 live births

Gaza Strip refugee camps West Bank refugee camps

1961-64 1975-78 1982 1961-64 1975-78 1982 Infancy 128 90 65 127 67 39 Neonatal 40 25 32 38 21 15 Post-neonatal 87 65 33 89 46 24 Gastroenteritis-malnutrition 54 44 17 57 20 7 Respiratory infections 37 24 13 20 20 9

Prematurity and congenital causes 27 16 32 18 13 12

Other causes 9 5 3 33 13 12

Gaza Strip registered deaths 1982 1985 Infancy 43.3 33.3 Neonatal 20.1 14.5 Post-neonatal 23.0 18.8 Diarrhoea 7.0 5.3

Other infectious and parasitic diseases 1.2 0.4

Diseases of nervous system 1.3 1.0

Diseases of respiratory system 11.6 8.5

Diseases of digestive system 0.4 0.8

Congenital anomalies 2.0 2.3

Perinatal causes including prematurity 18.2 12.6

Other causes 1.6 3.1

Sources: Puyet (1979); Abdalla and Guinena (1983); UNRWA (1987); Israel, MH (1986).

the figures in Table 8.7 show, there were twice as many deaths at age 1-11 months as in the first month of life and most of the post-neonatal deaths were attributed to gastroenteritis-malnutrition and respiratory diseases. At age one to four, the relative distribution of deaths associated with water-borne and air-borne infections may have been different but the level of mortality attributed to each was undoubtedly high. Moreover, even though, as Puyet (1979) points out, respiratory diseases such as pneumonia and

broncho-pnuemonia were often the terminal complications of other infectious diseases such as measles, there is sufficient evidence to conclude that both diarrhoea-related causes and respiratory deaths far outnumbered the deaths from notifiable diseases. This, necessarily approximate, breakdown of deaths by cause is consistent with the age pattern of mortality exhibited by the survey population between 1955 and 1965.

Since 1967, the immunisation programme has been expanded to include oral polio vaccine and to extend BCG vaccine, which had been given to school children, to infants (Israel, MH, 1986). Coverage has undoubtedly improved - among children registered at UNRWA and government Maternal and Child Health clinics between 80 and 85 per cent of infants received the complete course of inoculations in 1984 (Israel, MH, 1986, p.132). The vaccination completion rates for ash-Shati and ash-Shaja„iyya (see Chapter 10) are slightly higher and this is consistent with the suggestion that the study communities had relatively good access to health services. After 1967 the (reported) incidence of most notifiable infectious diseases declined (Table 8.6) but 70 child deaths were reported during a measles epidemic in 1981/82 (Israel, MH, 1986, p.134) and the clinic and hospital data indicates that the incidence of pertussis actually increased in the 1980s. However, it seems reasonable to assume that the total number of deaths caused by notifiable diseases, which had already reached a low level in the early 1960s, continued to decline after 1967.

A significant reduction in the number of child deaths from gastroenteritis and respiratory infections accounts for most of the improvement in child survival in the survey populations between the late 1960s and the 1980s. Evidence to support this assertion is provided by a comparison of the age distribution of infant deaths in the survey population (Table 8.3) and the reported deaths in the Gaza Strip camps (Table 8.7). In the Gaza camps in 1961-64, the post-neonatal mortality rate was more than double the neonatal mortality rate but by 1982 there was little difference between the two rates. In the study population in the early 1960s, mortality at ages 1-11 months was nearly three times higher than mortality in the first month of like but by the early 1980s, the neonatal rate was slightly higher than the post-neonatal rate (Table 8.3). Similar, if not greater, declines in deaths from gastroenteritis and respiratory infections would have occurred at ages 1 to 4.

The cause of death data for the Gaza camps indicate that, by the 1980s, more infant deaths were attributed to gastro-intestinal-malnutrition disorders than to respiratory infections. This contrasts with the data for the Gaza Strip which show that respiratory

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infections accounted for a larger proportion of infant deaths (Table 8.7). For the study population in the 1980s, the relatively even distribution of deaths at ages 1-35 months throughout the year indicates that the number of deaths associated with respiratory and gastrointestinal diseases are probably similar.

The published data show that by the 1980s the total number of deaths from causes related to prematurity and congenital abnormalities exceeded the number from either respiratory or gastroenteritis infections. The UNRWA figures indicate that 49 per cent of infant deaths in 1982 occurred during the first month of life and the corresponding figure derived from death registration data is 45 per cent for the years 1980-84. The estimated neonatal and post-neonatal mortality rates for ash-Shati and ash-Shaja„iyya in the period 1980-85 are 22 and 17 deaths per thousand (Table 8.3). Thus there is no doubt that in the study population in the 1980s, the number of deaths associated with endogenous causes in the neonatal period is greater than the number of infant deaths caused by infections, malnutrition and other exogenous factors. This is a radical shift from the pattern of mortality prevailing in the 1950s when approximately 70 per cent of the infants who died were aged between one and twelve months.