Study characteristics
The search strategy identified a total of 2012 records, and after removing duplicates and screening for relevance, 15 of them were included in the meta-analysis. Figure 1 illustrates the flow of information through the identification and screening phases of this systematic review. Table 1 presents the characteristics of the included studies. All studies were cross-sectional in design with representation from diverse geographic regions including the United States of America, USA (5 studies), Spain (2 studies), and one study each from Serbia, China, Brazil, Finland, Poland, Australia, Philippines, and Argentina. The source of data for the studies was vital registration systems, which represent the general population of samples. Additionally, all studies reported cause of death using ICD codes, ensuring consistency in the definition of outcomes across studies. Eight studies reported CVD as total CVD, and some [33, 37–40, 43–45, 47] reported CVD as a specific CVD type (IHD, stroke, or others). All included studies were published between 1998 and 2022, but data source covered a period from 1990 to 2019. Moreover, ten studies reported ASMR for premature CVD mortality by sex.
Quality Assessment
The NOS adopted version for cross-sectional design was used to assess the quality of the included studies. Out of the 15 studies, 13 were rated as very good, one was rated as good, and one was rated as satisfactory, with none being classified as poor. Consequently, all 15 studies were included in the analysis (Table 1).
Overall ASMR Estimates And Subgroup Analysis By CVD Types And Sex
Using a random effects model, Table 2 presents the summary of the pooled estimate of ASMR for premature CVD mortality, in overall and based on subgroup. The meta-analysis estimated the overall ASMR for premature CVD mortality to be 27.0 (95% CI: 20.13, 36.21) per 100,000 people, with a high degree of heterogeneity among the studies (I2 = 99%). Subgroup analysis showed a significant difference in the ASMRs for different types of CVD, with the ASMR for total CVD being the highest (ASMR = 96.04, 95% CI: 67.18, 137.31; I2 = 84%), followed by IHD (ASMR = 15.57, 95% CI: 11.27, 21.5; I2 = 92) and stroke (ASMR = 12.36, 95% CI: 8.09, 18.91; I2 = 97%). We also observed differences in ASMRs between sex, where males (ASMR = 37.50, 95% CI: 23.69, 59.37; I2 = 96%) demonstrated a higher rate than females (ASMR = 15.75, 95% CI: 9.61, 25.81; I2 = 99%). The forest plot for subgroup analysis for overall studies by CVD types, and sex was presented in the Supplement 3 (Figure S1-S2). To further explore sex-specific differences in CVD mortality, we generated forest plots for each CVD type (total CVD, IHD, and stroke) by sex. We excluded studies that only provided data for the combined male and female groups. Our analysis revealed that ASMR for all types of CVD, including IHD and stroke, was significantly higher for males than females. The test for subgroup differences yielded a p-value of less than 0.05, as shown in Fig. 2–4. When comparing specific CVD types, we found that the ASMR for males was 27.51 (95% CI: 17.89, 42.30) and for females was 9.30 (95% CI: 6.64, 13.03) for IHD (Fig. 3). Similarly, for stroke (Fig. 4), the ASMR for males was 15.18 (95% CI: 10.12, 22.77), while it was 7.23 (95% CI: 2.45, 21.29) for females.
Table 2
Summary of pooled ASMR per 100,000 population for premature cardiovascular mortality
Subgroup
|
Studies (n)
|
Random effect model
ASMR
per 100,000
|
95%
Confidence interval
|
Test for Heterogeneity
|
I2 (%)
|
T2
|
p
(Q test)
|
Overall study
|
15
|
27.00
|
20.13, 36.21
|
99
|
1.21
|
0
|
CVD types
|
|
|
|
|
|
|
|
Total CVDa
|
8
|
96.04
|
67.18, 137.31
|
84
|
0.33
|
< 0.01
|
|
IHDb
|
4
|
15.57
|
11.27, 21.51
|
92
|
0.39
|
< 0.01
|
|
Strokec
|
4
|
12.36
|
8.09, 18.91
|
97
|
0.29
|
< 0.01
|
|
Other typesd
|
3
|
19.79
|
8.41, 46.58
|
100
|
2.11
|
0
|
Sex
|
|
|
|
|
|
|
|
Male
|
10
|
37.50
|
23.69, 59.37
|
96
|
0.97
|
< 0.01
|
|
Female
|
10
|
15.75
|
9.61, 25.81
|
99
|
1.32
|
0
|
Country income levele
|
|
|
|
|
|
|
|
HICs
|
10
|
21.42
|
15.63, 29.37
|
99
|
1.16
|
0
|
|
MICs
|
6
|
90.58
|
56.40, 145.48
|
77
|
0.31
|
< 0.01
|
Time study (year)
|
|
|
|
|
|
|
|
1990–1999
|
4
|
16.35
|
8.35, 32.02
|
96
|
0.77
|
< 0.01
|
|
2000–2009
|
5
|
63.84
|
35.34, 115.31
|
98
|
1.27
|
< 0.01
|
|
2010–2019
|
10
|
19.93
|
13.56, 29.30
|
99
|
0.97
|
0
|
ASMR: age-standardized mortality rate; I2: I statistics; T2: Tau statistics; Q test: Cochran's Q test. p: p-value.
aTotal CVD death was based on ICD − 10 code: I00-I99 or ICD-9 codes: 350–459.
bIschemic heart disease (IHD) death based on ICD-10 (I20-I25) or ICD-9 (410–414)
cCerebrovascular disease or stroke death based on ICD-10 (I60-I69) or ICD-9 (430–438)
dOther types of CVD death including heart disease (ICD-10: I00-I09, I11, I13, I20- I51), heart failure (ICD-10: I50) and cardiac death ICD-10 (I21, I25, I40, I34, I35, I42, I45-I49, R96, Q20-Q24, Q87)
eAccording to World Bank’s classification. HICs = high income countries, MICs = middle-income countries (including upper middle-income countries and low middle-income countries)
Subgroup Analysis By Income Country Classification
Furthermore, stratifying by income country classification (Table 2) revealed a significant higher overall ASMR for premature CVD mortality in MICs (ASMR = 90.58, 95% CI: 56.40, 145.48; I2 = 77%) compared to HICs (ASMR = 21.42, 95% CI: 15.63, 29.37; I2 = 99%) (see forest plot Figure S3 in Supplement 3). In addition, we did the specific subgroup analysis for selected studies that reported total CVD (ICD-10 codes I00-I99 or ICD-9 codes 350–459) by country income level (see Forest plot Figure S4, in Supplement 3), where this analysis also demonstrated a higher ASMR estimate in MICs than HICs (ASMR = 111.11 vs. 78.21 respectively).
Subgroup Analysis By Study Time
The conducted a subgroup analysis of ASMR for premature CVD mortality based on the study time showed undulated pattern from, 1990–1999, 2000–2009, and 2010–2019. ASMR for premature CVD mortality was 16.35 (95% CI: 8.35, 32.02; I2 = 96%) for the 1990–1999 period, increased to 63.84 (95% CI: 35.34, 115.31; I2 = 98%) for the 2000–2009 period, and then declined to 19.93 (95% CI: 13.56, 29.30; I2 = 99%) for the 2010–2019 period (see Table 2 and Forest plot in Supplement 3, Figure S5). Similar undulated pattern was revealed when we conducted a subgroup analysis of premature CVD mortality rate by income country level based on the study time. We separately analysed the ASMR for HIC and MIC by study time, as shown in Table 3 (see comparing with original data in specific subgroup analysis) and Forest plots in Supplement 3, Figure S6-7. Our results showed that the trend in premature CVD mortality was similar in both HICs and MICs, with an increase from 1990–1999 to 2000–2009, followed by a decrease from 2000–2009 to 2010–2019. Specifically, in HICs, the ASMR increased from 16.35 (95% CI: 8.35, 32.02; I2 = 96%) in 1990–1999 to 40.47 (95% CI: 16.19, 101.22; I2 = 99%) in 2000–2009, and then decreased to 18.47 (95% CI: 11.89, 28.67; I2 = 99%) in 2010–2019. In MICs, the ASMR decreased from 172.55 (95% CI: 109.64, 271.55; I2 = 12%) in 1990–1999 to 50.89 (95% CI: 45.62, 56.77; I2 = 0%) in 2010–2019. It should be noted that MICs data during the period 1990–1999 were not available in any of the studies included in our meta-analysis. Our findings suggest that the trend of premature CVD mortality is consistent across income levels.
Table 3
Sensitivity analysis of pooled ASMR per 100,000 population from premature CVD mortality by excluding the studies outlier
|
After removed outlier
|
Comparison with original data
|
Subgroup
|
n
|
ASMR
(95% CI)
|
I2 (%)
|
n
|
ASMR
(95% CI)
|
I2 (%)
|
Overall study
|
13
|
31.20 (23.81, 40.89)
|
97
|
15
|
27.00 (20.13, 36.21)
|
99
|
CVD types
|
|
|
|
|
|
|
|
Total CVDa
|
6
|
46.69 (28.63, 76.15)
|
29
|
8
|
96.04 (67.18, 137.31)
|
84
|
|
IHDb
|
3
|
20.67 (12.41, 34.45)
|
74
|
4
|
15.57 (11.27, 21.51)
|
92
|
|
Strokec
|
3
|
12.23 (10.55, 14.17)
|
86
|
4
|
12.36 (8.09, 18.91)
|
97
|
Sex
|
|
|
|
|
|
|
|
Male
|
8
|
46.23 (31.95, 66.90)
|
93
|
10
|
16.12 (9.9, 26.25)
|
99
|
|
Female
|
8
|
18.87 (11.99, 29.70)
|
97
|
10
|
37.83 (24.10, 59.40)
|
96
|
Country income classificatione
|
|
|
|
|
|
HIC
|
9
|
26.53 (19.61, 35.91)
|
97
|
10
|
21.42 (15.63, 29.37)
|
99
|
|
MIC
|
5
|
121.56 (70.05, 210.95)
|
40
|
6
|
90.58 (56.40, 145.48)
|
77
|
Time study (year)
|
|
|
|
|
|
|
|
1990–1999
|
3
|
21.40 [14.68, 31.19)
|
68
|
4
|
16.35 (8.35, 32.02)
|
96
|
|
2000–2009
|
4
|
112.85 (64.87, 196.32)
|
85
|
5
|
63.84 (35.34, 115.31)
|
98
|
|
2010–2019
|
9
|
23.25 (16.76, 32.24)
|
97
|
10
|
19.93 (13.56, 29.30)
|
99
|
Specific subgroup analysis
|
|
|
|
|
|
HIC by study time
|
|
|
|
|
|
|
|
1990–1999
|
3
|
21.40 (14.68, 31.19)
|
68
|
4
|
16.35 (8.35, 32.2)
|
96
|
|
2000–2009
|
3
|
40.47 (16.19, 101.22)
|
97
|
3
|
40.47 (16.19, 101.22)
|
99
|
|
2010–2019
|
5
|
21.84 (14.99, 31.81)
|
96
|
6
|
18.47 (11.89, 28.67)
|
99
|
MIC by study time
|
|
|
|
|
|
|
2000–2009
|
3
|
172.55 (109.64, 271.55)
|
12
|
3
|
172.55 (109.64, 271.55)
|
12
|
|
2010–2019
|
3
|
22.10 (3.29, 148.74)
|
0
|
4
|
50.89 (45.62, 56.77)
|
0
|
Total CVDa by sex
|
|
|
|
|
|
|
|
Male
|
4
|
81.68 (23.63, 282.35)
|
0
|
5
|
181.86 (112.98, 292.76)
|
0
|
|
Female
|
4
|
32.36 (11.30, 92.68)
|
40
|
5
|
72.69 (30.04, 175.91)
|
85
|
IHDb by sex
|
|
|
|
|
|
|
|
Male
|
3
|
45.07 (24.44, 82.13)
|
0
|
4
|
27.51 (17.89, 42.30)
|
68
|
|
Female
|
3
|
11.18 (7.42, 16.86)
|
46
|
4
|
9.30 (6.64, 13.03)
|
83
|
Strokec by sex
|
|
|
|
|
|
|
|
Male
|
2
|
14.40 (0.65, 316.68)
|
11
|
3
|
15.18 (10.12, 22.77)
|
28
|
|
Female
|
2
|
10.54 (8.22, 13.50)
|
0
|
3
|
7.23 (2.45, 21.29)
|
99
|
n = number of studies, CVD = cardiovascular disease, ASMR = age standardized mortality rate (ASMR) per 100,000. Random effect model applied pool estimate of ASMR, 95% CI = 95% confident interval of estimated ASMR.
atotal CVD death was based on ICD − 10 code: I00-I99 or ICD-9 codes: 350–459.
bIschemic heart disease (IHD) death based on ICD-10 (I20-I25) or ICD-9 (410–414)
cCerebrovascular disease or stroke death based on ICD-10 (I60-I69) or ICD-9 (430–438)
dOther types of CVD death including heart disease (ICD-10: I00-I09, I11, I13, I20- I51), heart failure (ICD-10: I50) and cardiac death ICD-10 (I21, I25, I40, I34, I35, I42, I45-I49, R96, Q20-Q24, Q87)
eAccording to World Bank’s classification. HICs = high income countries, MICs = middle-income counties (including upper middle-income countries and low middle-income countries)
Outlier removed for each subgroup as below;
-
Overall study: Jin et.al, (2020) and Gómez-Martínez et al. (2018)
-
Total CVD: Yang et al. (2021) and Gawryszewski & Souza (2014)
-
IHD: Dani et al. (2022)
-
Stroke: Moryson & Stawińska (2022)
-
Male and female: Best et al. (2018) and Gómez-Martínez et al. (2018)
-
Study time year 1990–1999: Gómez-Martínez et al. (2018)
-
Study time year 2000–2009: Moryson & Stawińska (2022)
-
Study time year 2010–2019: Gómez-Martínez et al. (2018)
-
High-income countries: Gómez-Martínez et al. (2018)
-
Middle-income countries: Yang et al. (2021)
Sensitivity Analysis
We conducted a sensitivity analysis by excluding outliers identified using the Baujat plot for overall and subgroup ASMR analysis. Based on the criteria for outlier exclusion as suggested by the Baujat plot, we reanalysed the data with and without these outlier studies to assess the impact on the overall effect estimate, CI, and heterogeneity. The sensitivity analysis revealed an improvement in I2 for each subgroup after removing the outlier studies, indicating a reduction in heterogeneity and improved precision of the effect estimates (Table 3). Specifically, among the MIC (I2 decreased from 77–40%) and specific subgroups analysis (such as female stroke), removing outliers resulted in a significant decrease in heterogeneity, with I2 reducing from 99–0%. However, it is essential to note that despite the improvement in I2 after removing the outlier studies, the pattern and direction of the findings remained consistent with the results obtained before outlier removal. For instance, the ASMR for males remained higher than that for females, and the ASMR for MIC remained higher than that for HIC, both before and after outlier removal. Similarly, the undulated trend observed for other subgroups also remained consistent, with increases and decreases in ASMR from 1990–2019. These results suggest that while excluding outlier studies improved the precision of the effect estimates and reduced heterogeneity, it did not substantially alter the overall conclusions of the analysis.
Publication’s Bias
To assess publication bias in the included studies, we used funnel plots, Egger's test, and Begg's test. The funnel plot for all studies showed an asymmetrical distribution (Fig. 5a), indicating the possibility of publication bias or other sources of small-study effects. However, the Begg's and Egger's tests did not reach significance (p = 0.764 and p = 0.088, respectively), suggesting no evidence of publication bias in the meta-analysis. We also examined the funnel plot for studies that reported total CVD (ICD-10: I00-I99 or ICD-9: 350–459), which exhibited an almost symmetrical distribution (Fig. 5b). Furthermore, the Egger's and Begg's tests for total CVD were not significant (p = 0.559 and p = 0.084, respectively), indicating no presence of publication bias for total CVD. Therefore, based on our comprehensive assessment, we found no strong evidence of publication bias in our meta-analysis.