Bridging the gap in life expectancy of the aborigines in Taiwan

Chi Pang Wen1, Shan P Tsai2, Yaw-Tang Shih1 and Wen-Shen Isabella Chung1

1 National Health Research Institutes, Division of Health Policy Research, Taipei, Taiwan, ROC
2 University of Texas, School of Public Health Houston, Texas, USA

Correspondence: Dr SP Tsai, Medical Department, 910 Louisiana Street, Houston, Texas, USA. E-mail: shan.tsai{at}shell.com


    Abstract
 Top
 Abstract
 Methods and Materials
 Results
 Discussion
 References
 
Background Similar to the general population in Taiwan, the health of aborigines has steadily improved over the last 30 years, but the gap remains wide, especially in males, despite an infusion of substantial medical resources. The objectives of this study are to quantify the contribution of major causes of death to the gap in life expectancy and to propose initiatives to bridge the health gap between aborigines and the general population.

Methods This study included residents (slightly over 200000) from 30 ‘aboriginal townships’ in Taiwan. The gap in life expectancy between aborigines and the general population was analysed by decomposing these gaps according to major causes of deaths. This analysis quantifies the contribution of different causes of deaths to the gap in life expectancy between the two populations.

Results The overall mortality of aborigines in these townships was approximately 70% higher than the respective male and female general populations over the past 30 years. Mortality from infectious disease, cirrhosis of the liver, accidents, and suicide are substantially higher than the general population. The gap in life expectancy at birth in males was 8.5 years during 1971–1973, increasing to 13.5 years by 1998–2000, however, the gap in females remained relatively stable (8.0 years and 8.4 years, respectively). Of the 13.5-year difference in life expectancy in males, the differential mortality from diseases of the digestive system (mainly due to cirrhosis of the liver), accidents (from both motor vehicle and non-motor vehicle accidents), and infectious and parasitic disease contributed half (50%) of the gap in life expectancy. In females, the above primarily preventable causes of deaths accounted for 41% of the life expectancy gap.

Conclusions Based on the findings of this study, we suggest that future focus should be in the area of primary prevention in order to reduce the incidence of infectious and parasitic diseases, liver cirrhosis, and accidents.


Keywords Life expectancy gap, primary prevention, aborigines, mortality

Accepted 31 July 2003

There are nine aboriginal tribes in Taiwan, with a combined population of approximately 330 000 (1.5% of the total population in Taiwan). The aborigines in Taiwan are of Malayan or Polynesian origin. Their customs, language, and physical characteristics are similar to those of the native population of the South Seas. The aboriginal people were the original residents in Taiwan for at least 2000 years before the arrival of the Chinese in the 16th century. When the Chinese flocked to Taiwan in large numbers, the aborigines were gradually driven towards the mountainous interior districts. For centuries, all nine aboriginal tribes maintained a great deal of their indigenous socio-cultural heritage in their agrarian societies. This picture did not alter much until the past three decades, during which rapid industrialization in Taiwan markedly changed the traditional agricultural lifestyle of the aborigines. Many young aboriginal people temporarily migrated to work in large cities from the rural and mountain areas where they still permanently reside.

The economic and living standards are very low among aborigines as compared with the general population of Taiwan.1 Health disparities between aborigines and the general Taiwanese population have previously been reported.1–4 Higher overall mortality and lower life expectancy have been observed for decades. Accidental injuries, suicide, liver cirrhosis, infectious disease, and stomach cancer are known to be high among aborigines. Health risk factors such as alcohol drinking, cigarette smoking, and betel nut chewing are highly prevalent among aborigines.5–7 The causes of their lower health status are complex, but the lack of health services, and the social and economic inequality of aborigines may have played an important role.

The plight of the health of aborigines in Taiwan has been the concern of both politicians and public health workers. Although since early 1995, after the implementation of National Health Insurance,8,9 the aborigines, along with the general population in Taiwan, have enjoyed almost unlimited access to medical care and no co-payments for medical services are required for residents of these aboriginal townships. However, the large gap in life expectancy persists.1 The purpose of this study is to systematically review the mortality of aborigines over a 30-year period from 1971 to 2000, to quantify the contribution of major causes of death to the life expectancy gap, and to propose initiatives to bridge the health gap between the aborigines and the general population in Taiwan.


    Methods and Materials
 Top
 Abstract
 Methods and Materials
 Results
 Discussion
 References
 
Residents residing in the 30 townships known as ‘aboriginal townships’ are the subjects for this study. Approximately 80% of the residents in these townships are aborigines. These townships are located in remote mountainous regions in seven counties in Taiwan. They are: Taipei County–Wulai; Ilan County–Tatong and Nanao; Taoyuan County–Fuhsing; Hsinchu County–Chienshin and Wufong; Miaoli County–Taian; Taichung County–Hoping; Nantou County–Hsinyi and Jenai; Chiayi County–Wufong; Kaohsiung County–Maolin, Taoyuan and Sanmin; Pingtung County–Santi, Wutai, Machia, Taiwu, Laiyi, Chunjih, Shitzu and Mutan; Taitung County–Haitauan, Yenping, Tahjen, Chinfong and Lanyu; and Hwalien County–Hsiulin, Wanjung and Chochi. The average total population of these townships during 1998–2000 was slightly over 200 000, which accounted for less than 1% of the total population in Taiwan (Table 1).


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Table 1 Average population (1998–2000) of aborigines and Taiwan general population by age and gender

 
Annual computerized mortality data containing cause of death information from death certificates for Taiwan by township from 1971 to 2000 were acquired from the Department of Health; 1971 is the first year and 2000 is the last year that such data are available. The population data by townships were obtained from the Department of the Interior. The integration of these two data sets formed the basis for this study. Mortality excesses and deficits are expressed as standardized mortality ratios (SMR), which is the number of observed deaths among aborigines divided by the number of deaths expected if the death rates for the general population in Taiwan were in effect.10 The number of deaths that are expected is adjusted for age. The 95% CI for each SMR was calculated and its deviation from 1.00 was tested assuming a Poisson distribution for the observed deaths, using a two-sided test of significance.11 SMR over time (i.e. 1971–1973, 1984–1986, 1992–1994, 1998–2000) for major causes of deaths as well as the infant mortality rate for these periods were calculated. The years 1992–1994 were included because they are the three years before the initiation of the National Health Insurance and 1984–1986 is the middle of the study period.

Life expectancy for the above time periods was calculated using the life table method proposed by Chiang, which seems to be operationally more convenient in converting the age-specific death rate to the probability of dying.12 The number of years gained in life expectancy at birth is calculated by subtracting the life expectancy of the life table from the corresponding table with partial reduction or complete elimination of certain causes of death. The gap in life expectancy between aborigines and the general population was further evaluated, using the method proposed by Tsai et al., by decomposing the gap according to major causes of death.13 This analysis quantifies the contribution of different causes of deaths to the gap of life expectancy between aborigines and the general population. The residuals shown in Table 5 are calculated by subtracting the contribution of life expectancy of each individual cause separately from the gap obtained by all causes jointly.


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Table 5 Added years of life expectancy for aborigines at birth by reducing selected causes of death: 1998–2000

 

    Results
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 Abstract
 Methods and Materials
 Results
 Discussion
 References
 
Age distributions for both male and female residents who lived in the 30 aboriginal townships were similar to the general population (Table 1). In these townships, there was a slightly higher proportion of middle-aged (20–64 years) males and a lower proportion of middle-aged females when compared with the corresponding general population.

Table 2 displays the observed number of deaths and SMR for major causes of deaths over the four time periods for both males and females. The overall mortality of aboriginal townships was approximately 70% higher than the respective male and female general populations during the past 30 years. Infectious disease, primarily due to tuberculosis, was consistently elevated among aborigines. In 1998–2000, the SMR for tuberculosis was 5.3 for males and 8.3 for females. Another noticeable excess was cirrhosis of the liver, which was about five times higher than the general population. Death due to accidents, both motor vehicle and other accidents, was three times higher. The SMR were particularly elevated for non-motor vehicle accidents, including pesticide poisoning and all other subcategories. Deaths from suicide were also significantly elevated during the study period, although the SMR were lower in 1998–2000 compared with earlier years for both males (SMR = 2.4 compared with 3.2–4.4 during earlier periods) and females (SMR = 3.2 compared with 3.6–5.3).


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Table 2 Standardized mortality ratios (SMR) for selected causes of death by gender: aborigines

 
Table 3 shows infant mortality for aborigines and Taiwan for different time periods. There was a great improvement in infant mortality between 1971–1973 and 1984–1986 for both the aborigines and the general population; however, the rate remained steady from 1984–1986 to 1998–2000. The aborigines had twice the infant mortality during the entire 30-year period. For example, the mortality rate in 1971–1973 for male babies was 40.9 per 1000 for aborigines but only 17.5 per 1000 for the general population; the rate decreased to 16.5 and 7.1 per 1000 by 1998–2000.


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Table 3 Infant mortality (per 1000) between aborigines and Taiwan general population

 
Life expectancy at birth has been widely used as the one of the most important health indicators of a population. Table 4 compares the life expectancy at birth between the aborigines and Taiwan. In 1971–1973, the aborigines lived, on the average, 8 years less than the corresponding general population in Taiwan. By 1998–2000, the gap in life expectancy in males increased to 13.5 years (59.2 versus 72.7 years), although the gap in females remained approximately the same (70.0 versus 78.4 years) as in previous years.


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Table 4 Comparison of life expectancy at birth (in years) between aborigines and Taiwan general population

 
The relative importance of various causes of death can be measured by the gain in life expectancy when a specific cause of death is eliminated. The greater the gain, the more important it is. The potential gain (or added years of life) in life expectancy at birth during 1998–2000 for aborigines by reducing or elimination of selected causes of deaths is shown in Table 5. As expected, elimination of digestive system disease in aboriginal males would add 3.4 years of life at birth. Elimination of motor vehicle and non-motor vehicle accidents would add 2.1 years and 2.9 years, respectively. While only responsible for 5.7% of the total deaths, elimination of infectious disease among aboriginal males would add one year to the life expectancy at birth. It is noteworthy that eliminating cancer would have less of an impact than non-motor vehicle accidents, with only a gain in life expectancy of 2.4 years. Similar patterns were also seen for aboriginal females. The elimination of digestive system diseases would add 3.4 years of life expectancy for a newborn girl. However, the elimination of motor vehicle and non-motor vehicle accidents had a smaller impact on the gain in life expectancy (0.8 years and 1.7 years, respectively) due to their relatively lower mortality rate in females. The results of reduction in selected causes of death are generally in accord with the proportion of elimination of the particular disease. For example, a 50% reduction in digestive system diseases would add 1.6 years for males and 1.7 years for females.

Table 6 examines the gap in life expectancy in 1998–2000 for three selected ages (i.e. at birth, at 20, and 40 years) between aborigines and the general population in Taiwan and this difference in life expectancy was further decomposed into differential components due to various causes of death. The life expectancy gap decreased with increasing age; 13.5 years at birth, 12.0 years at age 20, and 8.4 years at age 40 for males. The corresponding figures for females were 8.4 years, 7.3 years, and 5.3 years, respectively. Of the 13.5-year difference in life expectancy at birth in males, 19.5% (2.6 years) of this difference is due to digestive system diseases, 14.1% (1.9 years) to non-motor vehicle accidents, 10.2% (1.4 years) to motor vehicle accidents, 6.7% (0.9 years) to respiratory diseases, 6.5% (0.9 years) to stroke, 6.1% (0.8 years) to infectious and parasitic diseases, 3.6% (0.5 years) to deaths from ill-defined conditions, and 2.8% (0.4 years) to cancer. In other words, the differential mortality from diseases of digestive system (primarily due to cirrhosis of the liver), accidents (from both motor vehicle and non-motor vehicle accdients), and infectious and parasitic diseases contributed 6.7 years (50%) of the gap in life expectancy between aboriginal males and males in the general population. The relative importance tended to increase with increasing age for diseases of the digestive system and infectious and parasitic diseases, but decrease for motor vehicle and non-motor vehicle accidents. The residual (the amount cannot be attributed to any single cause) accounts for 17.2%, which stems from the non-additive effects of reduced mortality from different causes, i.e. the sum of the years gained when the causes are eliminated separately is less than the gain if the same causes are eliminated by all causes as a group.13


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Table 6 Decomposition of the difference in life expectancy between aborigines and Taiwan general population: 1998–2000

 
Similar to their male counterparts, the most important contribution for females came from diseases of the digestive system, which accounted for 15.6% (1.3 years) of the life expectancy gap at birth between female aborigines and the corresponding general population. The contributions of infectious and parasitic diseases, stroke, and respiratory system diseases were slightly larger than for males and tended to increase with age. Accidents also played an important role in the gap of life expectancy in females although the magnitude of contribution was smaller than in males. The contribution of these primarily preventable diseases and causes of deaths (i.e. disease of digestive system, accidents, and infectious and parasitic diseases) accounted for 3.4 years (41%) of the gap in life expectancy among females.


    Discussion
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 Abstract
 Methods and Materials
 Results
 Discussion
 References
 
Life expectancy has been widely used as one of the most important health indicators of a population. Life expectancy at each specific age is an estimate of the future average life span for a person who survives to a given age. While relative risk expressed in terms of the SMR provides information from the standpoint of causation, life expectancy is in some instances the preferred measure because it has a clear intuitive meaning. This paper uses life expectancy as the primary measure for the implementation of various health care strategies.

Similar to the pattern seen in the general population in Taiwan, the health of the aborigines has steadily improved over the last 30 years. The pace of the improvement among female aborigines was about the same as that of the corresponding general population, thus the gap in life expectancy remained approximately the same, 8.0 years in 1971–1973 and 8.4 years in 1998–2000. However, the pace was much slower among male aborigines; an improvement of life expectancy of only 1.3 years as compared with 6.4 years in the general population during this period. Consequently, the life expectancy gap among males has widened from 8.5 years in 1971–1973 to 13.5 years in 1998–2000. In addition, when compared with Taiwan in their respective periods, many SMR of the aborigines showed a worsening trend; the most notable ones are all causes, tuberculosis, liver cirrhosis, stroke, and motor vehicle and other accidents. Thus, despite an infusion of substantial medical resources particularly since 1995, the gap in life expectancy between the aborigines and the general population has not been narrowed.

Health disparities are known to exist among aborigines and non-aborigines in many other countries such as Australia, Canada, New Zealand, and the US.14–18 Life expectancies are shorter among aborigines and incidence of infectious disease, cirrhosis of the liver, suicide, and accidental deaths has been particularly prevalent and significantly higher than the corresponding general populations. The pattern of life expectancy observed in this study is very similar to that of Australia. For example, life expectancy at birth of aborigines in Australia in the 1980s was 53–61 years and 58–65 years for males and females, respectively, which was 12–15 years shorter than the Australian general population (73 years for men and 78 years for women).17 These large gaps in life expectancy remain in the 1990s (56.9 years for aboriginal men and 61.7 years for aborigines women compared with 75.2 years and 81.1 years, respectively for non-aboriginal men and women).18 The absence of quality medical services during much of the period is no doubt important, and other socioeconomic and psychosocial factors could also play a critical role in determining the health of a population.

What could be done to bridge the gap in life expectancy between the aborigines and the general population in Taiwan? The most common choice, and may be the most logical one, is, and has been, to provide more or better medical services to the aborigines. This choice is in line with the common sense approach that ‘Better medical care should result in better health.’ In fact, health care utilization since 1995 among aborigines has been much higher than the general population.4 Most policy makers, including public health officials, continued to assume health inequalities would be diminished. However, as demonstrated in this study, only life expectancy for male aborigines kept up with the corresponding general population between 1992–1994 and 1998–2000, neither the infant mortality nor the infectious and parasitic disease mortality improved when compared before and after the initiation of the National Health Insurance in early 1995.

Among the three health policy options, i.e. primary prevention (promoting primary prevention for the entire population), secondary prevention (offering screening or early detection for the asymptomatic), and tertiary prevention (providing medical care and treatment for the sick),19 we believe the primary prevention would yield the largest number of years in life expectancy. Three causes of death, i.e. diseases of the digestive system, infectious and parasitic diseases, and accidents, which are particularly preventable through primary prevention, accounted for half of the gap in life expectancy between aborigines and the general population for males (6.7 years) and 41% (3.4 years) for females. The results of this study highlight the diminishing return in further investment in the medical care model approach, i.e. tertiary prevention, for the aborigines. For example, medical management is quite limited in its effectiveness in treating liver cirrhosis. In contrast, if alcohol consumption was curtailed through a primary prevention model, and cirrhosis was reduced or prevented, the resulting outcome would be far better than the medical model. Another example is the approach to reduce accidental deaths. While better treatment would improve the survival of injured victims, the effect would be limited by the continued high incidence of accidents among aborigines that would not be reduced by medical care. Many accidental deaths occur before medical care can be rendered, while others, despite the best care available, leave varying degrees of disability and sequela. In this case, primary prevention of accidents makes sense in the long run because accident incidence is reduced, thus reducing the need for medical care.

Secondary prevention, highly recommended by most public health professionals, could be effective for certain infectious diseases, certain cancers, diabetes, or heart disease. However, its limited impact on the health of the aborigines is illustrated by the small contribution of these diseases to the gap in life expectancy.

Results from this study clearly indicate the need for policy change toward this disadvantaged population. Providing free health care for aborigines is an important step in closing the gap in life expectancy between aborigines and the general population in Taiwan. A more comprehensive approach should include improving the socioeconomic status of the aborigines. Fewer than 5% of aboriginal males had any college education in 1980 as compared with 13% in the general male population; the corresponding figures for females were 2% and 7%, respectively.1 Unemployment rates among aborigines were substantially higher than the general population (15% versus 5% for men and 15% versus 4% for women).20 In addition, the inadequate health care (median number of physicians per 1000 population among aborigines was 0.33 as compared with 1.10 in the general population)1 before 1995 may have also contributed to their relatively poor health.

The influence of socioeconomic and environmental factors on the health of populations is well documented.21–23 It has long been recognized that factors such as the safety of neighbourhoods, economic conditions, the educational level of residents, occupational safety, medical care, and other social and behavioural risk factors are important determinants of health in a community. Socioeconomic disadvantages may result in inadequate nutrition during childhood, poor education, high unemployment, and psychosocial factors, which are causative to ill-health, and can occur despite access to good-quality medical care. The previous investments, primarily providing medical care and tertiary prevention, have not resulted in significant improvement in the health of aborigines. While there is still room for improvement in medical care, as reflected by the high SMR for tuberculosis and parasitic diseases, the future focus should be on primary prevention particularly of infectious disease, liver cirrhosis, and accidents in order to bridge the gap of life expectancy between the aborigines and the general population. Reducing the prevalence of smoking, alcohol drinking, and betel chewing as well as improving community health education of aborigines would have a long-term impact on their health. Finally, in addition to providing quality medical care, the government should make a firm commitment to supporting and enhancing the current programmes of social and educational equality and economic propensity for aboriginal people in Taiwan. We believe, only then will there be significant improvements in the health of aborigines.


KEY MESSAGES

  • Similar to the general population in Taiwan, the health of aborigines has steadily improved over the last 30 years, but the gap remains wide, especially among males, despite an infusion of substantial medical resources.
  • The gap in life expectancy at birth in males was 8.5 years during 1971–1973, but increased to 13.5 years by 1998–2000, however, the gap in females remained relatively stable; 8.0 years in 1971–1973 and 8.4 years in 1998–2000.
  • The differential mortality was especially large from infectious and parasitic disease, diseases of the digestive system (mainly cirrhosis of the liver), and accidents (from both motor vehicle and non-motor vehicle accidents). These primarily preventable causes of deaths accounted for 50% in males and 41% in females of the gap in life expectancy between aborigines and the general population in 1998–2000.
  • Based on the findings of this study, we suggest that future focus to reduce the gap between aborigines and the general population should be in the area of primary prevention.

 


    References
 Top
 Abstract
 Methods and Materials
 Results
 Discussion
 References
 
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