, DOI: 10.54608.annalsmedical.2021.17

Citation: Khazaei Z, et al. Burden of Alzheimer’s Disease and other Dementias in Elderly People in Asia: A Systematic Analysis for the Global Burden of Disease Study in 2019. Ann Med Health Sci Res. 2021;11:1496-1505.

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Abstract

Background: Alzheimer’s Disease (AD) is a progressive and damaging brain disease of unknown etiology. The goal of this study is to investigate the burden of AD in Asia in 2019. Materials & Methods: All data sources accessible from the 2019 Global Burden of Disease study were used to estimate prevalence, mortality and disability-adjusted life years of the Alzheimer’s disease and other dementias as well as Alzheimer’s disease’s attributable risk factors in Asia from 1990 to 2019. We estimated all-cause and cause-specific mortality, Years of Life Lost (YLLs), Years Lived with Disability (YLDs), Disability-Adjusted Life-Years (DALYs) and attributable risks. All estimates were presented as counts and age-standardized rates per 100,000 populations with Uncertainty Intervals (UIs). Results: The highest incidence, prevalence, mortality, burden of disease, YLL and YLD belonged to high-income areas and the lowest to middle-income areas. There is a positive and significant correlation between Human Development Index (HDI) and disease incidence (r=0.319, P<0.05) and the prevalence of the disease (r=0.325, P<0.05). The results revealed a positive and significant correlation between HDI and disease burden (DALY) in women (r=0.325, P<0.05). There is also a positive and significant correlation between HDI and YLD in both sexes (r=0.414, P<0.05). However, no positive and significant correlation was found between HDI and YLL (P>0.05). There incidence of AD in the elderly was positively and significantly related to the mean years of schooling (r=0.428, P<0.05). Also, life expectancy at birth was positively and significantly correlated with the burden of disease (DALY) (r=0.362, P<0.05) and YLL (r=0.317, P<0.05). The results also illustrated a positive and significant correlation between YLD and mean years of schooling (r=0.510, P<0.05) life expectancy at birth (r=0.397, P<0.05) and expected years of schooling (r=0.399, P<0.05). Conclusion: These estimates can be used to guide the elderly care planning and interventions. Hence, policymakers and health care providers need to be informed of these trends to provide appropriate services.

Keywords

Dementia; Alzheimer’s disease; Burden disease; DALY; Elderly

Abbreviations

HDI: Human Development Index; NCDs: Non-Communicable Diseases; GNI: Gross National Income; LEB: Life Expectancy at Birth; GDP: Gross Domestic Product

Introduction

One of the serious repercussions of the aging is the Alzheimer's Disease (AD), which is a dominant and well-known cause of dementia (70%-60%) in the elderly population. AD begins with the progressive cognitive decline and its prevalence and incidence varies according to population structure worldwide. The incidence of dementia increases exponentially with age, peaking in the seventh and eighth decades of life. In light of the prolonged life expectancy and population aging, there has been an explosion of research on this disease. [1,2]

The genetics of AD is a complex subject from an epidemiological perspective. This disease is a progressive neurodegenerative disorder of unknown etiology. Age, sex, blood pressure, cardiovascular diseases, alcohol consumption, and socioeconomic status are considered risk factors for AD. [1,3]

Today, 24.3 million people suffer from dementia, with 4.6 million new cases of dementia being reported each year. That is, every 7 seconds, one new case of AD is recorded worldwide. In 2000, the number of people aged +65 in the world was estimated at 420 million. With a change ratio of 7 to 12, this figure is estimated to reach one billion by 2030. [1,4]The highest prevalence and rates of dementia is in people over 60 years of age in North America and Western Europe, followed by Latin America, China, and the western Pacific states. The greatest rise in the incidence of AD is projected in developing countries, and it is estimated to triple from 249 million people per year in 2000 to 690 million people in 2030. The growing rate of dementia cases varies in the world, and the figures are estimated to surge by 100% in developed countries from 2001 to 2040. China, India and other countries in South Asia and the Western Ocean are expected to experience a 300% growth. About 70% of these cases are attributed to AD. [5-7]

AD is a major public health issue associated with huge social and economic costs in the world. In this regard, a pressing issue is covering the costs of healthcare services to people with AD. 43% of these patients need a high level of care. The total global cost of dementia in 2010 was estimated at $604 billion. In the United States, AD is estimated to incur $172 billion costs annually. AD also imposes a considerable financial burden with high levels of anxiety and depression being reported in caregivers of these patients. AD is a leading cause of mortality worldwide. [7-9] As far as AD and Human Development Index (HDI) are concerned, the burden of AD-related problems is lower in areas with high HDI. [10] HDI is the gist of human development measures that assess the average success of a country in the three main dimensions of human development, i.e. a long and healthy life, access to knowledge and appropriate living standards.

Given the prevalence of AD in the world, it is necessary to explore its causes in order to plan and manage financial and human resources to curb its prevalence. It is essential for each country to take necessary interventions by comparing its data with other countries regarding the effect of socio-economic situation on the causes of depression.

Given the growing cases of AD in recent years, raising awareness about the disease is crucial to plan and manage financial and human resources for the prevention of this disease. Despite the rising burden of AD, little is known about its medical costs and further studies are required for this purpose. The main goal of this study is to evaluate AD burden in the elderly in Asia based on data taken from the World Bank in 2019.

Materials and Methods

This is a correlational analytical study that aims to investigate the trend of AD burden and its relationship with the HDI during 1990-1990 in Asia. The burden of disease study is the most comprehensive and accurate global epidemiological research. The burden of disease study is the outcome of 359 diseases and 84 health risk factors in 195 countries and regions worldwide (including developed and developing countries). Information on the burden of disease, YLL and YLD is publicly accessible on Global Burden of Disease website.

Disability-Adjusted Life Years (DALY)

DALY is a health distance index that measures years of life lost, whether due to premature death or non-fatal illness. This index was defined and used in the study of Global Burden of Disease (GBD) to measure the burden of disease.

Years of Life Lost (YLL)

To identify and prioritize the causes of premature death, YLL was introduced by the World Health Organization in the study of the global burden of disease. This index relies not only on the number of deaths but also on the age of the deceased at the time of death, so that the younger the age of the deceased at the time of death, the greater the years of life lost. YLL describe years in which an individual can lead a useful life, but were lost due to the premature death.

Years Lived with Disability (YLD)

It refers to years a person has lost due to the disease-related disability.

Human Development Index (HDI)

The HDI, estimated annually for all developing and developed countries, is publicly available on the World Health Organization website for researchers. In this study, data related to this index is derived from the WHO website.

The HDI, reported by the World Health Organization, provides the latest information on global development and embraces national, regional, and global estimates. In the Human Development Report, countries are assigned to several groups including very high human development, high human development, medium human development and low human development based on HDI. The numerical value of HDI is between 0 and 1. This index shows how far countries have progressed towards the highest possible value (i.e.1), thereby allowing comparisons between countries. The HDI, as the gist of human development measures, measures the average success of a country in the three main dimensions of human development, namely a long and healthy life, access to knowledge and living standards.

Statistical Analysis

In this study, the two-variable correlation method was used for data analysis to examine the correlation of the burden of Alzheimer's disease and other dementias with HDI. A significance level of P<0.05 was considered. The analyses were made using Stata software 12 (Stata Corp, College Station, TX, USA).

Results

According to the results of Table 1 in 2019, the incidence of AD in the elderly (+70 years old) worldwide were 987.3 per 100,000 in men and 1413.3 per 100,000 in women. The prevalence of this disease in both sexes was 8997.6 per 100000 and the associated death rate of the disease was 326.1 per 100000. According to the results, the DALY index for this disease (4538.9 per 100,000), YLL (3650.9) and YLD (1342.2) were calculated for 2019.Figure 1 shows the burden trend for YLD, YLL, and DALY during 1990-2019 periods in four continents. As can be seen, the highest burden of disease index, YLL and YLD were related to the Americas and the lowest to the Africa. The trend of DALY in Asia suggests that the trend of AD in the elderly (+70 years ago) in this continent has taken an upturn, increasing from 864.8 in 1990 to 1186.3 in 2019. The YLL in Asia has taken an upturn from 1990 to 2019, surging from 629.5 in 1990 to 840.3 in 2019. In exploring the trend of the index of YLD, the results manifested the rising trend of this index in Asia during 1990 to 2019. As can be seen, this index soared from 235.3 in 1990 to 345.9 in 2019.

Figure 1: Shows the burden trend for YLD, YLL, and DALY during 1990-2019 periods in four continents.Trend of burden Alzheimer's disease and other dementias in 1990- 2019 in four regions of the world (Source: GBD Compare).

Table 2 shows the burden of disease (DALY) as well as YLL and YLD indices by gender and country in Asia in 2019. As is depicted, the lowest burden of AD in the elderly (+70 years old) (DALY) in 2019 belonged to India (2910.98) and the highest to Japan (7084.64). The lowest burden of disease (DALY) in women was related to Bangladesh (3007.37) and the highest to Japan (8352.23). In men, the lowest burden of disease was reported in Brunei (2366.21) and the highest in Japan (5351.44)

Table 2: Burden of Alzheimer's disease and other dementias in Asia in 2019 (Source: GBD Compare).

The lowest values of YLD in both sexes were reported in India (653.99) and the highest in Japan (2061.13). In women, the lowest YLD was related to India (693/27) and the highest to Japan (2570/15) and in men, the lowest YLD had been registered in India (609/36) and the highest in Kuwait (1585/58). The lowest YLL in both sexes was related to India (1935/32) and the highest to Japan (5023/51). In women, the lowest YLL was recorded in India (2174/37) and the highest in Japan (5782/07), and in men, the lowest YLL was related to India (1613/61) and the highest to Japan (3986/31).

Table 3 displays the incidence and prevalence of AD in the elderly (+70 years old) in Asia by country and gender. As can be seen, the highest incidence of AD in both sexes was registered in Japan (1798/74 per 100,000) and the lowest incidence in Pakistan (719.75 per 100,000). The highest incidence of AD in men was reported in Iran (1473/67) and in women was registered in Japan (2181/99). The highest prevalence of this disease in both sexes was recorded in India (13602.2) and the lowest in Pakistan (4866.02). The highest prevalence of AD in men was reported in India (11397/6) and in women was reported in Japan (16513).

Table 3: Incidence and Prevalence of Alzheimer's disease and other dementias in Asia in 2019(Source: GBD Compare).

Figure 2 shows the trend of AD-related indices in the elderly (+70 years old) during 1990-2019 period. As can be seen, the trend of incidence, prevalence, mortality, burden of disease (DALY), YLL and YLD were greater in higher income regions. Moreover, the highest incidence, prevalence, mortality, burden of disease (DALY), YLL and YLD were reported in high-income regions and the lowest in middle-income regions.

Figure 2: AD and other dementias in 1990- 2019 by world bank income level (Source: GBD Compare).

Figure 3-Figure 7 shows the association of HDI with incidence, prevalence, mortality, burden of disease (DALY), YLL, YLD in the elderly patients with AD (+70 years old) in Asia in 2019. As can be seen, there is a positive and significant correlation between HDI and disease incidence in both sexes (r=0.319, P<0.05). This correlation was positive and significant in women (r=0.423, P<0.05) but non-significant in men (r=0.132, P>0.05).

Figure 3: Correlation of HDI with incidenceof Alzheimer's disease and other dementias in Asia in 2019 by sex.

Figure 4: Correlation of HDI with Prevalenceof Alzheimer's disease and other dementias in Asia in 2019 by sex.

Figure 5: Correlation of HDI with DALY of Alzheimer's disease and other dementias in Asia in 2019 by sex.

Figure 6: Correlation of HDI with DAYL of Alzheimer's disease and other dementias in Asia in 2019 by sex.

Figure 7: Correlation of HDI with YLL of Alzheimer's disease and other dementias in Asia in 2019 by sex.

The results indicated a positive and significant correlation between HDI and the prevalence of disease in both sexes (r=0.325, P<0.05), which was again significant in women (r=0.420, P<0.05) but non-significant in men (r=0.137, P >0.05).

The results showed revealed a positive and significant correlation between HDI and burden of disease (DALY) in woman (r=0.325, P<0.05), but this positive correlation was non-significant in both sexes (r=0.277, P>0.05) and in men (r=0.111, P>0.05).

The results also manifested a positive and significant correlation between HDI and YLL in both sexes (r=0.414, P<0.05), which was also significant in women (r=0.499, P<0.05) but non-significant in men (r=0.219, P>0.05).

The results of YLD analysis suggested that HDI was no positively and significantly related to YLL in both sexes (r=202, P>0.05), in men (r=0.292, P>0.05) and in women (r=0.063, P>0.05).

Table 4 shows the relationship between components of HDI and all indices of AD in the elderly (+70 years old). Clearly, there is a positive and significant correlation between the incidence of AD in the elderly and the mean years of schooling (r=0.428, P<0.05) and expected years of schooling. The results also showed that the prevalence of AD was positively and significantly related to the mean years of schooling (r=0.383, P<0.05), life expectancy at birth (r=0.295, P<0.05) and expected years of schooling (r=0.337, P<0.05).

Table 4: Correlation of indexes Alzheimer's disease and other dementias to decomposites of human development index in Asia in 2019.

There is also a positive and significant correlation between life expectancy at birth and burden of disease (DALY) (r=0.362, P<0.05) and YLL (r=0.317, P<0.05).

As shown by the results, YLD was also positively and significantly correlated with mean years of schooling (r=0.510, P<0.05), life expectancy at birth (r=0.397, P<0.05) and expected years of schooling (r=0.399, P<0.05).Figure 8-Figure 10 depicts the share of metabolic and genetic factors associated with AD in the elderly (+70 years) in all AD-related indices. As can be seen, the share of behavioral factors relative to metabolic in YLL was 719.1 vs. 387.1 in men and 192.7 vs. 550.3 in women. It suggests that behavioral factors in men and metabolic factors in women have a crucial role in determining YLL. The results of YLD analysis showed that the share of behavioral and metabolic factors was 296.2 and 149.1 in men and 86.6 and 228.3 in women, respectively. As is evident, behavioral factors have a greater share in men and metabolic factors have a greater share in women. On the other hand, the analysis of the burden of disease (DALY) in men shows that the share of behavioral and metabolic factors is 1015.3 vs. 536.3 in men and 279.3 vs. 778.8 in women, indicating that the proportion of metabolic factors in the burden of disease in women.

Figure 8: Alzheimer’s disease and other dementias attributable to metabolic and behavioral risks by four world region in 2019 (Source: GBD Compare).

Figure 9: Alzheimer’s disease and other dementias attributable to metabolic and behavioral risks by four world region in 2019 (Source: GBD Compare).

Figure 10: Alzheimer’s disease and other dementias attributable to metabolic and behavioral risks by four world region in 2019 (Source: GBD Compare).

Discussion

AD is the most common and recognized cause of dementia, which ensues progressive and irreversible brain dysfunction. During the decades of demographic transition, the burden of the disease has posed a huge challenge to the health system. [11,12] AD can provoke depression and anxiety in people around the patient on top of the disability and mortality of the patient. 46.8 million People with dementia live worldwide and it is predicted to double every 20 years. [13,14]

The results of this study revealed a positive and significant correlation between HDI and disease incidence in both sexes (r=0.319, P<0.05) which was positive and significant in women (r=0.423, P<0.05) but non-significant in men (r=0.132, P>0.05). 

The highest incidence of AD in both sexes was reported in Japan whereas Pakistan had the lowest incidence of AD in both sexes in the world. The highest and lowest prevalence in both sexes were reported in India and Pakistan, respectively. Disparity in the rate of Alzheimer's in different countries could also be attributed to discrepancy in socioeconomic status, heterogeneity in study design, differences in health care systems, various diagnostic methods, and heterogeneity in demographic characteristics. Today, the increase in the incidence and prevalence of AD in the world could be ascribed to factors such as the higher efficiency of diagnostic tests and increased awareness of people about Alzheimer's disease over time. [3-15]

In recent years, the incidence of dementia has surged in developing countries. China and the Pacific have a high incidence of dementia. The rate was 5% in the People's Republic of China, 2% in Japan, and 4% in Taiwan, as well as 5 million in the European Union, 2.9 million in the United States and 1.5 million in India. [16-18]  The highest incidence of HDI-related AD in the world was reported in countries with higher HDI. The lowest incidence of HDI-related AD was reported in countries with medium HDI. In Japan, there were more than 4.6 million Japanese with dementia in 2013, which is expected to reach 7 million by 2025, indicating that one in five elderly people in Japan suffer from dementia. [14]

The results of a study by Han et al. in 2018 illustrated a significant connection between the rising rate of AD and some components of HDI, such as socioeconomic factors, the low level of education and lifestyle. [19]

A 2005 study by Wilson et al. found that there was a significant positive correlation between the incidence of AD in children from birth to adulthood and HDI. This association was also related to the reduced risk of AD in adulthood in people with higher socioeconomic status. [10]

A 1997 study by Evans et al. showed that there was no significant relationship between the incidence of AD in people with high socioeconomic status and HDI. The observed difference in the incidence of AD was significantly linked to education but irrelevant to job and income components. [20]

Social and economic developments have exerted a major impact on the incidence, prevalence and mortality of AD. In high-income countries, the risk of AD is on rise. Factors such as gender, education and life expectancy at birth are known as HDI-related risk factors for AD. The incidence and death of AD are linked to the economic growth of societies. Statistics shows that the majority of AD-induced cases have been reported in high-income countries. [19]

Also, the results of this study displayed a positive and significant correlation between HDI and disease prevalence in both sexes (r=0.325, P<0.05). This correlation was significant in women (r=0.420, P<0.05). But non-significant in men (r=0.137, P>0.05). Moreover, the higher incidence of AD in countries with higher HDI could be explained in terms of advanced diagnostic methods, higher economic status and meticulous data recording. HDI is the average of the geometric development of normal indices that measure the success of each dimension (optimal life, knowledge, and longevity). Beyond income and possessions, this index assesses long-term life satisfaction of individuals in the society, underscoring HDI and the fact that the ultimate goal of development programs should be providing conditions for healthy, creative and happy living for human beings.

Finally, caution should be exercised in interoperating such studies because in addition to the epidemiological risk factors for AD, the inherent limitations of ecological studies should also be taken into account. Issues such as differences in screening criteria and differences in reported age groups have to be taken into account. By the introduction of primary prevention methods, epidemiological studies timely treatment, and follow-up of AD patients, especially in less developed countries, effective steps can be taken to inhibit the incidence of the disease.

Conclusion

The incidence of AD in the elderly continues to pose a public health challenge and there are social inequalities regarding the burden of the disease. These estimates can be helpful for public health planning in order to provide a basis for planning and interventions, especially for areas with a higher incidence of the disease. The disproportionate surge in AD cases and consequently dementia, in addition to the composition of the population in different countries, can be linked to other factors that require further research in these countries.

Limitations and Problems

This study was constrained to countries whose data are recorded on the burden of disease website. Given the fact that the present study is an ecological study, exposure or outcome data were not collected at the individual level, but data were taken from all exposed individuals in a specific community or time frame. A main drawback of these studies is ecological fallacy, which attributes characteristics observed at the group level to the individual. To avoid this error, the results of such studies should be interpreted with caution.

Acknowledgments

Declaration of conflicting interests

The authors declare that they have no conflict of interest.

Availability of data and materials

The datasets generated during the present study can be provided by the corresponding author upon reasonable request.

Author Contributions

Elhamgoodarzi and Zaherkhazaei carried out the design of the study and carried out analyzing the data and prepared the manuscript. Kobra Rashidi and Victoria Momenabadi critically reviewed the manuscript, applied comments and finalized the manuscript. All authors have read and approved the content of the manuscript.

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