Results
Among world
countries available in this study sample, 149 countries (75%) had a Life
expectancy at birth greater than 65 years while
50 countries (25%) had
a Life expectancy at birth less/equal to 65 years.
Table 1 presents
the bivariate associations between country characteristics and Life expectancy
at birth. Bonferroni adjustment of the p value for the evaluation of these
multiple comparisons is p < .007.
Table 1 Country characteristics by Life expectancy at
birth
Life expectancy at birth greater than 65 years
(N=149)
|
Life expectancy at
birth less/equal to 65 years
(N=50)
|
|||||
Country characteristics
|
Mean
|
standard deviation
|
Mean
|
standard deviation
|
F value
|
p value
|
GDP PER CAPITA (CURRENT US$)
|
19258.6
|
23322.0
|
2243.7
|
3600.3
|
25.7
|
<.0001
|
ACCESS TO
ELECTRICITY
(% OF POPULATION)
|
91.7
|
16.3
|
35.5
|
22.5
|
361.4
|
<.0001
|
HEALTH EXPENDITURE
PER CAPITA
(CURRENT US$)
|
1397.8
|
2040.8
|
115.2
|
152.7
|
<.0001
|
|
IMPROVED SANITATION
FACILITIES
(% OF
POPULATION WITH ACCESS)
|
86.4
|
16.9
|
31.6
|
18.2
|
351.2
|
<.0001
|
IMPROVED WATER
SOURCE
(% OF POPULATION WITH ACCESS)
|
94.6
|
7.7
|
69.6
|
14.7
|
217.8
|
<.0001
|
LABOR FORCE, FEMALE
(% OF TOTAL LABOR FORCE)
|
40.0
|
9.2
|
44.0
|
8.0
|
7.4
|
0.0070
|
70.6
|
78.0
|
32.8
|
1.5
|
0.2134
|
Analysis of Variance for continuous variables yielded the following differences:
- countries with Life expectancy at birth greater or equal than 65.65 years compared with countries with Life expectancy at birth less/equal to 65 years have a higher Gross domestic product (GDP), 7.425.7, p < .0001
- . and exhibited more health expenditure per capita, F=18.8, p < .0001
- and showed a higher % of population with access to electricity, F=361.4, p < .0001
- and were found to have more population with access to improved sanitation facilities, F=351.2, p < .0001
- and a greater % of population with access to improved water source, F=217.8, p < .0001
- and reported a lower % of female labor force, F=7.4, p < .007
- and finally didn’t present a statistically significantly difference in term of % of population exposed to PM2.5 levels of air pollution exceeding World Health Organization guideline value
Next,
countries variables were included as possible contributors to a CART model
evaluating Life expectancy at birth (Figure 1).
Figure 1 Classification tree.
Figure 1 Classification tree.
Each pentagon
represents a decision point. For the decision point, the predictor variable and
cut point are presented. Final groups with high and low outcome probability are
represented by rectangles in the figure and include outcome frequencies and
percentages. Shaded rectangle represent subgroups with relatively high rates of
countries with high Life expectancy at birth, nonshaded rectangles, relatively
low rates.
The % of
population with access to electricity was the first variable to separate the
sample into two subgroups. Countries with a % of population with access to
electricity greater or equal than 56.3
were more likely to have high Life expectancy at birth compared to countries
not meeting this cutoff (95.3% vs. 12.2%).
Of the countries
with % of population with access to electricity greater than 56.3 , a further
subdivision was made again with the % of population with access to electricity.
Countries who reported having a % of population with access to electricity greater
or equal than 89.6 were more likely to have high Life expectancy at birth compared
to countries not meeting this cutoff (99.2% vs. 78.6%).
After
splitting twice the data based on % of population with access to electricity,
the other variables don’t impact on Life expectancy at birth.
The model
classified 92% of the sample correctly, 95% of countries with Life expectancy
at birth greater or equal than 65 years (sensitivity) and 82% of countries
with Life expectancy at birth lower than 65 years (specificity).