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Chapter 4: Subnational trends in longevity and mortality

This part presents a summary of mortality and longevity trends for the total population of subnational areas (regional council and territorial authority areas).

Abridged life tables for regional council areas (regions) were first produced in 1994 for the period 1990–92. In 1998, regional life tables for the 1995–97 period were published, although these have now been revised. This report contains summary results from the 1990–92 to 2005–07 abridged life tables for regions. The 1990–92 life tables use a different population measure than later periods (see table 1.02).

In addition, abridged life tables have been produced for selected territorial authority areas for 1995–97 to 2005–07, where death numbers are sufficient to produce reliable life tables. Because life tables cannot be reliably produced for many subnational areas, standardised death rates (SDRs) have also been derived for all regional council and territorial authority areas for the periods 1995–97 to 2005–07. As with life tables, SDRs allow for the different age-sex composition of each area. However, deriving SDRs is less sensitive than life tables to age groups with zero deaths.

To minimise annual fluctuations in mortality rates, the mortality measures are calculated for a three-year period. Nevertheless, all subnational mortality and longevity trends should be interpreted with caution. Death and population numbers can fluctuate from period to period. In addition, the stated residence of the deceased may not reflect the geographic area(s) where that person spent most of their life.

It should be noted that data from the abridged life tables may differ from data from the complete life tables.

Regional life expectancy at birth

Although New Zealanders’ life expectancy at birth has increased by 9.0 years for males and by 6.7 years for females in the last 30 years, there are some significant regional differences in life expectancy (figures 4.01 and 4.02). According to the 2005–07 abridged life tables for regional council areas, life expectancy at birth ranged from 73.8 to 79.4 years for males, and 78.1 to 83.2 years for females (table 4.01). Possible reasons for regional variations in mortality and life expectancy are discussed in the ‘Factors affecting mortality patterns’ section below.

The regional life tables indicate that five regions have experienced both male and female life expectancies at birth that are consistently above the New Zealand average over the last decade: Auckland, Wellington, Tasman, Canterbury, and Otago (figures 4.03 to 4.06). Conversely, life expectancy in Gisborne region was significantly below the national average, with both male and female life expectancy being over four years lower than the New Zealand average in 2005–07. Other regions with life expectancies consistently below the national average over the last decade were Northland, Bay of Plenty, Hawke’s Bay, Manawatu-Wanganui, West Coast, and Southland. Life expectancies in the remaining regions (Waikato, Taranaki, Nelson, and Marlborough) varied above or below the national average.

According to the abridged life tables, between 2000–02 and 2005–07 life expectancy at birth increased by 1.8 years for males and 1.0 year for females. All regions experienced life expectancy gains between these periods, except Gisborne where female life expectancy decreased by almost a year. However, the size of the gains varied significantly. Northland, Auckland, and Wellington regions were the only regions to experience gains greater than the national average for both males and females.

Figure 4.01

Map, New Zealand.

Figure 4.02

Map, New Zealand.

Table 4.01

Table, Life expectancy at birth.

Table 4.01 continued

Table, Life expectancy at birth.

Figure 4.03

Graph, Male and female life expectancy at birth.

Figure 4.04

Graph, Male and female life expectancy at birth.

Figure 4.05

Graph, Male and female life expectancy at birth.

Figure 4.06

Graph, Male and female life expectancy at birth.

Regional life expectancy at age 65 years

The 2005–07 abridged life tables indicate that having reached the age of 65 years, New Zealanders can, on average, expect to live a further 18.2 years for males and 20.9 years for females (table 4.02). Only two regions had both male and female life expectancy at age 65 years above the national average: Auckland (18.9 and 21.4 years) and Wellington (18.4 and 21.2 years).

Between the periods 2000–02 and 2005–07, life expectancy at 65 years improved by 1.4 years for males and 0.6 years for females. All regions had gains in male life expectancy at age 65. Female life expectancy at age 65 also increased, although small falls were experienced in Gisborne and Tasman. However, the size of the gain varied significantly. Northland, Wellington, West Coast, Otago, and Southland were the only regions to have increases that were greater than the national average for both males and females.

Table 4.02

Table, Life expectancy at age 65 years.

Table 4.02 continued

Table, Life expectancy at age 65 years.

Territorial authority areas life expectancy at birth

There are 40 territorial authority areas where death and population numbers are considered sufficient to produce abridged life tables for 2000–02 and 2005–07, and 39 territorial authority areas for 1995–97. Nevertheless, because of fluctuations in death and population numbers, these abridged life tables should be interpreted with caution.

The 2005–07 life tables indicate that 13 of the 40 territorial authority areas had higher life expectancy at birth than the national average for both males and females. These 13 areas include seven cities (North Shore, Waitakere, Auckland, Tauranga, Upper Hutt, Wellington, and Christchurch) and six districts (Rodney, Waipa, Western Bay of Plenty, Kapiti Coast, Tasman, and Waimakariri). A similar pattern was observed for the 2000–02 period, although males in Western Bay of Plenty district, females in Upper Hutt city, and both males and females in Waipa district had slightly lower life expectancy than the national average. Possible reasons for the variations in mortality and life expectancy are discussed in ‘Factors affecting mortality patterns’ below.

Figure 4.07

Figure, Life expectancy at birth.

Note: ci = city; di = district

Standardised death rates

For many areas, death and population numbers are too small for constructing reliable abridged life tables, let alone complete life tables. Standardised death rates (SDRs) provide a summary measure of the mortality experience for each area, but also allow for the different age-sex composition of each area. However, they are meaningful only in comparison with similarly computed rates. Using the direct method of standardisation, SDRs indicate the overall death rate (deaths per 1,000 population) if the observed age-sex specific death rates were applied to a standard population.

SDRs have been calculated for all regional council and territorial authority areas for the periods 1995–97 to 2005–07 (table 4.03). The estimated resident population of New Zealand by age (0, 1–4, 5–9, 10–14, ..., 80–84 and 85+ years) and sex at 30 June 1996 is used as the standard.

Table 4.03

Figure 4.08

Map, North Island.

Figure 4.09

Map, South Island.

SDRs for New Zealand overall decreased from 7.5 deaths per 1,000 population in 1995–97 to 6.5 deaths per 1,000 population in 2000–02, and 5.8 deaths per 1,000 population in 2005–07. The decrease between 2000–02 and 2005–07 was reflected in all regions and almost all territorial authority areas except South Waikato and Hurunui districts where rates increased, and Ruapehu and Westland districts where there was no change.

SDRs for regions in 2005–07 ranged from 5.4 to 7.9 deaths per 1,000 population, compared with a range of 5.9 to 8.2 deaths per 1,000 population in 2000–02, and a range of 7.2 to 9.4 deaths per 1,000 population in 1995–97. Auckland, Tasman, Nelson, and Canterbury regions had lower SDRs than the New Zealand average in 1995–97 to 2005–07. In contrast, Northland, Bay of Plenty, Gisborne, Hawke’s Bay, Manawatu-Wanganui, West Coast, and Southland regions had SDRs above the national average for all three periods. Wellington, Marlborough, and Otago experienced SDRs close to the national average for the three periods.

Among territorial authority areas, SDRs ranged from 3.9 to 7.9 deaths per 1,000 population in 2005–07, compared with 4.7 to 10.1 deaths per 1,000 population in 2000–02, and 5.2 to 10.0 deaths per 1,000 population in 1995–97. The SDRs, similar to the life expectancy results, suggest some geographic differences within regions. For example:

  • Auckland region, with an SDR of 5.4 in 2005–07, includes territorial authority areas with SDRs ranging from 4.6 (North Shore city) to 6.7 (Papakura district).
  • Waikato region, with an SDR of 6.0 in 2005–07, includes territorial authority areas with SDRs ranging from 5.2 (Otorohanga district) to 7.4 (South Waikato and Waitomo districts).
  • Bay of Plenty region, with an SDR of 6.0 in 2005–07, includes territorial authority areas with SDRs ranging from 5.3 (Tauranga city) to 7.8 (Opotiki district).
  • Manawatu-Wanganui region, with an SDR of 6.3 in 2005–07, includes territorial authority areas with SDRs ranging from 5.8 (Manawatu district) to 7.4 (Ruapehu district).
  • Wellington region, with an SDR of 5.6 in 2005–07, includes territorial authority areas with SDRs ranging from 4.9 (South Wairarapa district) to 6.8 (Porirua city).
  • Canterbury region, with an SDR of 5.6 in 2005–07, includes territorial authority areas with SDRs ranging from 4.5 (Selwyn district) to 5.9 (Timaru district).

Factors affecting mortality patterns

The reasons for subnational differences in longevity and mortality are difficult to identify precisely and are probably due to a combination of interrelated factors, including the proportion of the population who are Māori, the proportion of the population who smoke (or have smoked), the proximity to health and hospital services, the degree of urbanisation, and socio-economic factors.

Compared with non-Māori, life expectancy at birth for 2005–07 was an estimated 8.6 years lower for Māori males and 7.9 years lower for Māori females at the national level. Based on ethnic population estimates at 30 June 2006 (Statistics NZ, 2006), the highest Māori proportions at the regional level were in Gisborne (47 percent), Northland (31 percent), Bay of Plenty (28 percent), and Hawke’s Bay (24 percent). These are regions where male and female life expectancy at birth was consistently below the national average for 1990–92 to 2005–07 (figures 4.03 to 4.06). In contrast, the lowest Māori proportions were in Otago, Tasman, and Canterbury (all 7 percent), and Nelson (9 percent). These are regions which consistently appear to have life expectancies near or above the national average.

At the territorial authority area level, the pattern is similar. The highest Māori proportions in 2006 were in the districts of Chatham Islands (63 percent), Kawerau (60 percent), Wairoa (59 percent), Opotiki (57 percent), Gisborne (47 percent), Far North (43 percent), Whakatane (42 percent), Waitomo (40 percent), Ruapehu (39 percent), and Rotorua (36 percent). With the exception of Chatham Islands, these areas are among those where life expectancies are below the national average and/or SDRs are above the national average.

Regionally, the proportion of the population who smoke also appears to have a strong inverse linear correlation with life expectancy (figures 4.10 and 4.11). At the 2006 Census, the proportion of the population aged 15 years and over who were smoking regularly was lowest in Tasman region (19 percent of males and 16 percent of females), Canterbury (20 percent and 17 percent), Wellington (20 percent and 18 percent), Auckland (20 percent and 16 percent) and Otago (20 percent of males and 18 percent of females). In contrast, the highest proportions were in Gisborne (28 percent of males and 30 percent of females), West Coast (25 percent and 24 percent), Northland (25 percent of both males and females), Hawke’s Bay (24 percent of both), and Southland (24 percent of males and 23 percent of females) regions.

Figure 4.10

Figure, Male life expectancy by smoking propensity.

Figure 4.11

Figure, Female life expectancy by smoking propensity.

Among territorial authority areas, the lowest smoking proportions in 2006 were in North Shore city (16 percent of males and 12 percent of females), Wellington city (17 percent and 13 percent), Selwyn district (17 percent and 14 percent), Waimakariri district (18 percent and 17 percent), Rodney district (18 percent of males and 16 percent of females), Kapiti Coast district (18 percent and 17 percent), Auckland city (19 percent and 13 percent), and Tasman district (19 percent of males and 16 percent of females). In contrast, the highest proportions were in Chatham Islands territory (39 percent of males and 42 percent of females), and in the districts of Kawerau (34 percent of males and 39 percent of females), Wairoa (32 percent and 35 percent), Opotiki (30 percent and 34 percent), Waitomo (29 percent of males and 31 percent of females), Ruapehu (28 percent and 30 percent), South Waikato (28 percent and 30 percent), and Buller (28 percent of males and 27 percent of females).

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