amhsr-open access medicla research journals
Zaher Khazaei1, Kobra Rashidi2, Victoria Momenabadi3 and Elham Goodarzi4*
 
1 Department of Paramedical, Hamadan University of Medical Sciences, Hamadan, Iran
2 Department of Nursing, Lorestan University of Medical Sciences, Khorramabad, Iran
3 Department of Public Health, School of Health, Bam University of Medical Sciences, Bam, Iran
4 Department of Health Research, Lorestan University of Medical Sciences, Khorramabad, Iran, Email: elhamgoodarzi.1370@yahoo.com
 
*Correspondence: Elham Goodarzi, Department of Health Research, Lorestan University of Medical Sciences, Khorramabad, Iran, Email: elhamgoodarzi.1370@yahoo.com

, DOI: 10.54608.annalsmedical.2021.17

Citation: Khazaei Z, et al. Burden of Alzheimerís 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.

Index Rate per 100,000
Male Female Both
Incidence 987.3(802.6-1170) 1413.3(1182.1-1640.7) 1226.4(1015.8-1437.1)
Prevalence 6999.5(5804.4-825.2) 10516.5(8809.6-12295.1) 8973.6(7557.9-10528.9)
Death 249.9(59.8-687.3) 385.6(97.1-994) 326.1(82.3-849.2)
YLL 2615.3(611.5-7270.2) 3650.9(919.4- 9527.5) 3650.9(919.4- 9527.5)
YLD 1044.9(723.8-1418.6) 1574.6(1107-2127.7) 1342.2(393.1-1806.9)
DALY 3660.3(1607-8252.4) 5225.6(2405.5-11044) 4538.9(2033.6-9859.1)

Table 1: Alzheimer's disease and other dementias in the world in 2019(Source: GBD Compare).

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)

Country YLL YLD DALY
M F Both M F Both M F Both
Afghanistan 3732.623 3507.184 3614.09 1185.035 1179.304 1182.022 4917.659 4686.488 4796.112
Armenia 3431.553 3812.703 3665.283 1417.664 1745.558 1618.736 4849.217 5558.261 5284.02
Azerbaijan 2692.026 3075.964 2922.11 1117.775 1396.057 1284.542 4472.021 4206.652 3617.192
Bahrain 2511.531 3243.203 2864.707 1051.326 1299.619 1171.177 3562.856 4542.822 4035.884
Bangladesh 2162.072 2217.36 2187.743 956.9617 790.0054 879.4407 3119.034 3007.365 3067.184
Bhutan 2496.069 2878.35 2684.916 825.1935 816.3563 820.8279 3321.262 3694.706 3505.744
Brunei 1722.861 2797.371 2341.773 643.3464 1179.118 951.9477 2366.207 3976.489 3293.721
Cambodia 2770.654 3509.157 3228.679 742.9361 1091.502 959.119 3513.59 4600.659 4187.797
China 2163.379 3417.286 2845.412 1026.984 1660.165 1371.388 3190.363 5077.45 4216.8
Georgia 2164.091 3180.236 2747.264 1420.602 1994.534 1793.195 3377.758 4860.849 4228.914
India 1613.608 2174.373 1935.322 609.3661 693.276 653.9925 2711.067 3086.954 2910.978
Indonesia 2103.833 2990.488 2605.499 691.032 1018.723 876.4384 2794.865 4009.211 3481.937
Iran 3686.098 3796.9 3741.756 1577.376 1589.727 1583.58 5263.474 5386.627 5325.336
Iraq 2928.746 3440.58 3201.752 1198.927 1446.603 1331.034 4127.673 4887.183 4532.786
Israel 2561.626 3604.666 3145.797 1113.243 1668.109 1424.005 3674.87 5272.775 4569.802
Japan 3986.31 5782.077 5023.511 1365.129 2570.15 2061.126 5351.44 8352.228 7084.637
Jordan 2677.077 2840.025 2757.03 1196.685 1256.324 1225.948 3873.761 4096.35 3982.978
Kazakhstan 2530.058 3092.986 2908.136 1087.134 1481.801 1352.203 3617.192 4574.788 4260.339
Kuwait 3705.145 4315.736 3935.792 1585.582 1889.874 1700.527 5290.728 6205.609 5636.319
Kyrgyzstan 3275.213 3848.258 3632.565 1387.107 1786.177 1635.968 4662.32 5634.435 5268.533
Lao People's Democratic Republic 2212.18 3225.176 2758.007 734.982 1127.002 946.2124 2947.162 4352.178 3704.22
Lebanon 3318.407 4139.663 3770.613 1410.496 1643.165 1538.61 4728.904 5782.828 5309.222
Malaysia 2413.748 3018.794 2718.757 826.6255 1186.882 1008.234 3240.374 4205.676 3726.991
Maldives 3111.903 3664.792 3378.23 1023.986 1351.5 1181.75 4135.889 5016.292 4559.98
Mongolia 2485.767 2899.306 2737.643 1054.875 1393.131 1260.898 3540.642 4292.437 3998.542
Myanmar 2314.71 3470.222 3006.052 766.8756 1174.12 1010.53 3081.585 4644.342 4016.582
Nepal 1836.078 2523.612 2192.81 726.43 748.0327 737.6387 2562.508 3271.645 2930.448
Oman 2543.175 3414.452 2962.148 983.6239 1256.695 1114.936 3526.799 4671.146 4077.083
Pakistan 2135.434 2557.186 2342.664 710.2131 697.7018 704.0657 2845.647 3254.888 3046.729
Philippines 2532.46 3186.467 2921.755 777.8357 1092.301 965.0195 3310.296 4278.768 3886.774
Qatar 2055.708 2286.444 2121.052 820.7656 889.9888 840.3694 2876.474 3176.432 2961.421
Saudi Arabia 2749.074 3663.83 3107.578 1084.804 1454.671 1229.759 3833.878 5118.501 4337.337
Singapore 2540.057 3649.352 3155.925 978.8314 1636.793 1344.124 3518.888 5286.144 4500.05
Sri Lanka 2336.578 3291.384 2896.988 754.0907 1152.462 987.9089 3090.669 4443.846 3884.897
Syrian Arab Republic 3044.748 3025.929 3035.727 1240.928 1222.664 1232.172 4285.676 4248.593 4267.899
Tajikistan 2462.319 3263.794 2893.951 1003.36 1446.976 1242.268 3465.678 4710.77 4136.22
Thailand 2768.141 3923.016 3425.255 929.7976 1418.109 1207.642 3697.938 5341.125 4632.897
Timor-Leste 2171.153 2844.601 2517.87 710.2001 949.0087 833.148 2881.353 3793.61 3351.018
Turkey 3344.327 4245.02 3842.923 1466.155 1738.751 1617.056 4810.482 5983.77 5459.979
Turkmenistan 2940.375 3823.416 3479.896 1264.73 1813.851 1600.232 4205.105 5637.267 5080.128
United Arab Emirates 2186.553 2285.979 2221.51 892.6295 945.9741 911.3846 3079.182 3231.953 3132.894
Uzbekistan 1817.74 2184.887 2041.934 827.7778 1098.711 993.2202 2645.518 3283.598 3035.154
Viet Nam 3205.251 4906.207 4289.052 823.0317 1374.286 1174.275 4028.283 6280.493 5463.327
Yemen 2795.876 3215.725 3009.378 1136.147 1328.724 1234.076 3932.023 4544.448 4243.455
Republic of Korea 2478.913 3847.785 3287.29 929.2544 1747.486 1412.455 3408.168 5595.271 4699.745
Democratic People's Republic of Korea 1873.572 3246.762 2819.866 748.1586 1329.143 1148.527 2621.731 4575.905 3968.392

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).

Country Incidence Prevalence
M F Both M F Both
Afghanistan 1216.73 1222.695 1219.866 8143.646 8345.556 8249.808
Armenia 1359.688 1551.445 1477.278 9165.69 11321.35 10487.59
Azerbaijan 1110.847 1301.109 1224.866 7323.807 9168.751 8429.434
Bahrain 1046.752 1260.587 1149.97 7339.279 9062.419 8171.036
Bangladesh 860.6695 763.8145 815.6979 6373.562 5355.412 5900.816
Bhutan 799.2615 789.0031 794.1938 5525.557 5570.344 5547.682
Brunei 679.1704 1207.048 983.2253 4564.61 7988.038 6536.486
Cambodia 738.2726 1064.963 940.8879 5110.24 7498.723 6591.593
China 931.9648 1443.423 1210.161 6869.627 11205.19 9227.856
Georgia 1378.609 1738.962 1612.548 8553.786 11712.25 10366.45
India 1390.612 1914.346 1691.081 11397.56 15240.35 13602.19
Indonesia 696.8359 1015.5 877.135 4778.837 7080.569 6081.148
Iran (Islamic Republic of) 1473.672 1477.553 1475.622 10417.68 10743.01 10581.1
Iraq 1158.617 1362.093 1267.148 8095.667 9817.337 9013.984
Israel 1025.34 1490.512 1285.867 7160.124 10830.15 9215.581
Japan 1274.732 2181.986 1798.744 8850.816 16513.01 13276.35
Jordan 1136.554 1192.519 1164.014 8025.399 8561.478 8288.435
Kazakhstan 1084.253 1361.633 1270.549 7225.122 9774 8937.018
Kuwait 1433.011 1644.21 1512.791 10461.45 12495.61 11229.85
Kyrgyzstan 1339.842 1589.599 1495.591 8922.043 11437.08 10490.42
Lao People's Democratic Republic 730.3675 1097.808 928.3533 4988.503 7622.212 6407.611
Lebanon 1330.694 1495.881 1421.65 9479.76 11093.99 10368.6
Malaysia 770.9453 1068.343 920.8662 5620.575 8114.595 6877.832
Maldives 965.8054 1237.862 1096.855 6761.961 9064.398 7871.048
Mongolia 1073.496 1301.785 1212.541 6984.122 9111.259 8279.709
Myanmar 765.952 1149.108 995.1936 5228.167 8038.464 6909.566
Nepal 726.5878 734.9739 730.939 4934.218 5171.108 5057.13
Oman 975.4679 1206.9 1086.757 6879.652 8729.596 7769.238
Pakistan 729.979 709.1625 719.7507 4867.056 4864.954 4866.023
Philippines 783.6504 1060.962 948.719 5268.325 7430.151 6555.143
Qatar 838.1949 941.9743 867.5848 5903.965 6579.993 6095.413
Saudi Arabia 1061.009 1371.371 1182.643 7545.677 10064.02 8532.647
Singapore 937.3983 1508.229 1254.317 6361.564 10501.21 8659.854
Sri Lanka 737.2889 1089.014 943.7286 5263.69 7945.896 6837.972
Syrian Arab Republic 1198.144 1194.001 1196.158 8381.314 8475.857 8426.636
Tajikistan 1028.324 1347.331 1200.125 6661.595 9464.93 8171.325
Thailand 875.2037 1269.635 1099.632 6178.685 9370.371 7994.727
Timor-Leste 712.8565 941.8066 830.7288 4919.924 6604.725 5787.324
Turkey 1350.1 1565.096 1469.115 9671.998 11627.08 10754.27
Turkmenistan 1239.015 1608.37 1464.683 8196.038 11644.65 10303.07
United Arab Emirates 895.4348 976.051 923.7781 6217.614 6770.947 6412.157
Uzbekistan 867.3843 1081.841 998.34 5640.311 7425.624 6730.492
Viet Nam 791.2814 1270.666 1096.732 5534.788 9171.494 7851.994
Yemen 1120.992 1290.817 1207.352 7661.815 9061.648 8373.66
Republic of Korea 874.8746 1540.664 1268.052 6200.688 11449.75 9300.482
Democratic People's Republic of Korea 732.7926 1264.088 1098.919 4964.941 8817.914 7620.104

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).

HDI components Incidence Prevalence DALY YLL YLD
r P-value r P-value r P-value r P-value r P-value
Gross national income per 1000 capita 0.034 P>0.05 0.043 P>0.05 0.014 P>0.05 -0.031 P>0.05 0.082 P>0.05
Mean years of schooling 0.428 P<0.05 0.383 P<0.05 0.275 P>0.05 0.172 P>0.05 0.51 P<0.05
Life expectancy at birth 0.263 P>0.05 0.295 P<0.05 0.362 P<0.05 0.317 P<0.05 0.397 P<0.05
Expected years of schooling 0.334 P<0.05 0.337 P<0.05 0.291 P>0.05 0.221 P>0.05 0.399 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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