Investigation Regarding the Correlation Between HDI and ...

[Pages:12]HL Biology IA

Anthony Hans

Jan 2016

Investigation Regarding the Correlation Between HDI and Mortality Rates due to Stroke

Research Question

What is the correlation between HDI and mortality rate due to stroke (measured in number of deaths per 100,000 of population), in countries with a HDI of above 0.75?

Background Research

Stroke is a cardiovascular disease that involves a lack of blood flow to the brain (National Stroke Association, n.d.). This can occur in several ways: hemorrhagic strokes occur when a weak blood vessel in the brain leaks, or if an aneurysm (a localized swelling of a blood vessel) bursts inside the brain; an embolic stroke occurs if a plaque or clot fragment formed elsewhere in the body, travels up the brain and blocks a small blood vessel there; and a thrombotic stroke is caused by a clot that formed inside one of the brain's blood vessel. All deprive sections of the brain from receiving sufficient oxygen, resulting in the death of the brain's neurons. Collectively, all of the different types of strokes kill six million individuals per year worldwide (World Heart Foundation, 2016).

Figure 1: Diagram showing a hemorrhagic stroke involving an aneurysm

Stroke, and other diseases such as coronary heart disease and Alzheimer's disease, are noncommunicable; that is, they are not transmitted from person to person, as infectious diseases carried by viruses or bacteria are (World Health Organization, 2015). Instead, they are caused due to risk factors, such physical inactivity or smoking. For this reason, advances technology and civil engineering which has helped in preventing and curing transmissible diseases (examples being vaccines limiting the effect of bacterial/viral diseases, and proper sewage treatment improving public hygiene and therefore health)

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may not necessarily work to slow the growing prevalence of non-communicable diseases, which are not caused by transmissions.

In this investigation, HDI (human development index) will be used as the metric by which development is measured. This is an index incorporating education, GNI per capita, and healthcare, using various indicators to measure each component and therefore the overall HDI (Human Development Report, 2015). An HDI value of 0.75 or higher can therefore be a reasonable indicator of a developed country.

Although certainly not as prominent as other non-communicable diseases, such as coronary heart disease or cancer ? both of which are the leading causes of death in most developed countries ? stroke is by no means insignificant. Even if a stroke attack does not claim the lives of its victims, the devastation it so often causes to the afflicted and their families are hugely paralyzing. Therefore, I have devoted this investigation to the study of stroke's prevalence, in hopes of better understanding it in the larger picture.

Therefore, this research aims to determine the impact of human development on the number of mortalities caused by strokes; where human development is measured by HDI, and the number of mortalities is taken per annum and per 100,000.

Hypothesis

It can be predicted there is a negative correlation between the HDI of a country and the number of lethal stroke cases there.

This is because when very high HDI countries are concerned, strokes are more easily treatable with advanced healthcare, allowing stroke patients a higher recovery rate. Therefore, despite a higher life expectancy and more people suffering from strokes, highly developed countries might be able to treat strokes more easily than other diseases such as cancer or coronary heart disease, hence reducing the mortality rate due to strokes

Therefore, the hypotheses for statistical testing are as follows:

Null Hypothesis: HDI has no impact on the mortality rate due to stroke. Alternative Hypothesis: HDI will have a negative correlation on the mortality rate due to stroke

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Materials

l Microsoft Excel (used for all calculations and data processing) l HDI database (for this, the Human Development Reports published by the UN will be used, which

may be found in this link: ) l WHO database on mortalities due to cerebrovascular diseases (may be found in this link:

, note that the death estimates for 2000 and 2012 is used) l World Bank database on total population (may be found in this link: ) Data from these sources are chosen for two reasons: reliability (as the UN and World Bank can be considered as reliable and trustworthy sources for such data due to the nature of their organization), and a lack of other databases.

Methodology & Trial Investigation

The following trial investigation was conducted with a selection of seven nations, which can also be used to demonstrate the methodology of this investigation. These countries are: Austria, Denmark, Germany, Greece, Hungary, Portugal, and Spain. These countries are chosen as they are all European OECD nations, and therefore should have reasonably similar cultural and economic status, reducing the possible impact of unrelated outside factors such as lifestyle habits or dietary preferences. The correlation should therefore be reasonably strong, demonstrating that this investigation will work.

Firstly, data regarding the population, human development index, and population will be obtained from their respective databases for the years 2000 and 2012 (the only years when the WHO has presented data regarding causes of mortality on their website):

Table 1: Raw data showing the estimated death counts due to stroke, population and the HDI of selected countries in the specified years

Country

Austria Denmark Germany Greece Hungary Portugal

Spain

Human Development Index

2000 0.836 0.862 0.855 0.799 0.769 0.782 0.827

2012 0.884 0.921 0.915 0.865 0.823 0.827 0.874

Estimated death counts due to

stroke (in '000s of deaths)

2000

2012

8.8

5

5.2

3.6

82.4

59.9

22.9

20.7

18.8

13.3

22.8

12.8

36.6

29.6

Population

2000

2012

8,011,566 8,429,991

5,339,616 5,591,572

82,211,508 80,425,823

10,805,808 11,045,011

10,210,971 9,920,362

10,289,898 10,514,844

40,263,216 46,773,055

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To calculate death rates, the estimated death counts due to stroke can be divided by the population. This is the death rate due to stroke per person; to find the more conventional death rate per 100,000 population, the number can be multiplied by 100,000.

Sample calculations: Austria's death rate due to stroke per 100,000 population in 2000

=

8.8 = 8011566 = 0.001098412

100,000 = ? 100,000 = 0.001098412 ? 100,000 = 109.8 (Note that the final result is in 1 decimal place, as the data found on death counts is also in 1 decimal place.)

Table 2: Processed data showing the mortality rates caused due to strokes

Country

Mortality rates due to stroke per person

Mortality rates due to stroke per 100,000 population

2000

2012

2000

2012

Austria

0.001098412

0.000593120

109.8

59.3

Denmark

0.000973853

0.000643826

97.4

64.4

Germany

0.001002293

0.000744786

100.2

74.5

Greece

0.002119231

0.001874149

211.9

187.4

Hungary

0.001841157

0.001340677

184.1

134.1

Portugal

0.002215765

0.001217327

221.6

121.7

Spain

0.000909018

0.000632843

90.9

63.3

From here, it is a simple matter of averaging the death rates and HDI for both years, then comparing the two values for correlation:

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Table 3: Average mortality rates per 100,000

population due to stroke and HDI of selected

countries of during the years 2000 and 2012

Country

Average human development index

Average mortality rate due to stroke

per 100,000 population

Austria

0.860

84.6

Denmark

0.891

80.9

Germany

0.885

87.4

Greece

0.832

199.7

Hungary

0.796

159.1

Portugal

0.804

171.7

Spain

0.851

77.1

Chart 1: the relationship between HDI and mortality rates due to stroke per 100,000

population in trial nations

250.0

Death rate due to stroke per 100,000 population

200.0

150.0

100.0

50.0

0.0 0.780

0.800

0.820

0.840

0.860

Human development index

0.880

5 0.900

The investigation will follow exactly the same method, except with a larger number of countries.

Investigation and Results

The database used in obtaining HDI information divides countries based on four categories: very high HDI countries (countries with a HDI above 0.8 as of 2014), high HDI countries (between 0.7 to 0.8), medium HDI countries (between 0.55 to 0.7) and low HDI countries (below 0.55). Therefore, the

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countries categorized as having a "very high HDI" will be used in this investigation, as relatively few of them have a HDI below 0.75 during 2000 (which is the minimum HDI used for this investigation, as stated in the research question). As there are relatively few countries in this category ? only 49 ? and a few of them either lack data (such as Liechtenstein) or have a population that is relatively small (such as Singapore or Hong Kong), random sampling is not necessary; only 18 of these countries have sufficient data, an HDI that is consistently above 0.75 and a population size greater than 10 million since 2000, so these 18 countries shall be used.

The results are as follows:

Table 4: Raw data showing the HDI, death counts due to stroke and total population of nations with HDIs above 0.75 on the years 2000 and 2012

Country

Human development index

Death count due to stroke (in '000s of

deaths)

Total population

2000

2012

2000

2012

2000

2012

Argentina

0.762

0.831

27.4

28.2

19,153,000 22,728,254

Australia

0.898

0.932

12.2

11.0

37,057,453 42,095,224

Belgium

0.874

0.889

8.6

7.4

10,251,250 11,128,246

Canada Chile

0.867 0.752

0.910 0.827

15.5 7.4

13.5 8.4

30,769,700 15,170,387

34,751,476 17,388,437

Czech Republic 0.821

0.867

16.9

10.4

10,255,063 10,510,785

France Germany

0.848 0.855

0.886 0.915

40.9 82.4

34.4 59.9

60,912,498 82,211,508

65,659,790 80,425,823

Greece Italy

0.799 0.829

0.865 0.872

22.9 67.3

20.7 58.7

10,805,808 56,942,108

11,045,011 59,539,717

Japan

0.857

0.888

132.1

120.6 126,843,000 127,561,489

Korea (Republic of) Netherlands

Poland

0.821

0.877 0.786

0.893

0.920 0.838

41.6

12.5 66.8

27.8

8.8 64.5

22,840,218

15,925,513 38,258,629

24,763,353

16,754,962 38,063,164

Portugal

0.782

0.827

22.8

12.8

10,289,898 10,514,844

Spain

0.827

0.874

36.6

29.6

40,263,216 46,773,055

United Kingdom

0.865

0.901

62.1

46.3

58,892,514 63,700,300

United States

0.883

0.912

169.3

133.6 282,162,411 314,102,623

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Table 5: Processed data showing the mortality rate caused by stroke in the selected nations in 2000 and 2012

Country

Mortality rate due to stroke per person

2000

2012

Mortality rate due to stroke per

100,000 population

2000

2012

Argentina

0.001432383

0.001241697

143.2

124.2

Australia

0.00032908

0.00026096

32.9

26.1

Belgium

0.000840013

0.000661172

84.0

66.1

Canada

0.000503748

0.000387472

50.4

38.7

Chile

0.000490413

0.000482589

49.0

48.3

Czech Republic

0.001647081

0.000988891

164.7

98.9

France

0.00067176

0.000524081

67.2

52.4

Germany

0.001002107

0.000744576

100.2

74.5

Greece

0.002114838

0.001870679

211.5

187.1

Italy

0.001182507

0.000985131

118.3

98.5

Japan

0.001041133

0.000945319

104.1

94.5

Korea (Republic of)

0.001819974

0.00112458

182.0

112.5

Netherlands

0.000787218

0.000522311

78.7

52.2

Poland

0.001745275

0.001693969

174.5

169.4

Portugal

0.00221199

0.001213221

221.2

121.3

Spain

0.000909327

0.000632348

90.9

63.2

United Kingdom

0.001054875

0.000726532

105.5

72.7

United States

0.000600084

0.000425269

60.0

42.5

Table 6: the average HDI and mortality rates due to stroke during the years 2000 and 2012

Country

Argentina

Average human development index

0.796

Mortality rate due to stroke per 100,000

population 133.7

Australia

0.915

29.5

Belgium

0.881

75.1

Canada

0.889

44.6

Chile

0.790

48.7

Czech Republic

0.844

131.8

France

0.867

59.8

Germany

0.885

87.3

Greece

0.832

199.3

Italy

0.850

108.4

Japan

0.872

99.3

Korea (Republic of)

0.857

147.2

Netherlands Poland

0.899 0.812

65.5 172.0

Portugal

0.804

171.3

Spain

0.850

77.1

United Kingdom

0.883

89.1

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Chart 2: Scatter graph showing the relationship between HDI and Mortality rate due to stroke in

countries with HDIs above 0.75

250.0

Mortality rate per 100,000 population caused by stroke

200.0

150.0

100.0

50.0

0.0 0.750

0.770

0.790

0.810

0.830

0.850

Human development index

0.870

0.890

0.910

y = -803.25x + 787.78 R? = 0.37128

Here we can observe that there is one outlier with a mortality rate of 48.7 per 100,000 due to stroke, and a HDI of 0.790 (the value found in the bottom left of the other data points on the graph); this belongs to Chile. If this is taken out of consideration, we can see that the scatter graph forms a loose linear correlation, as displayed on the graph. The linear correlation therefore allows the use of a Pearson's product-moment coefficient for statistical testing.

Statistical Testing

To conduct a Pearson's correlation test, some values must be assigned: the variable X can be the mortality rate due to stroke, whereas Y is the human development index, and N denotes the number of countries. The total sum of each column is then found. Then, new columns for the values of XY, X2, and Y2 is needed. The result is as follows:

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