The authors have declared that no competing interests exist.
Stroke incidence data with methodologically acceptable design in Southeast Asia countries is limited. This study aimed to determine incidence of age-, sex- and subtype-specific first-ever stroke (FES) in Vietnam.
We conducted a hospital-based retrospective study, targeting all stroke cases hospitalized at a solo-provider hospital in our study site of Nha Trang from January 2009 to December 2011 with International Classification of Diseases, 10th revision (ICD-10) codes I60-69. We calculated positive predictive values (PPVs) of each ICD-10-coded stroke by conducting a detailed case review of 190 randomly selected admissions with ICD-10 codes of I60-I69. These PPVs were then used to estimate annual incident stroke cases from the computerized database. National census data in 2009 was used as a denominator.
2,693 eligible admissions were recorded during the study period. The crude annual incidence rate of total FES was 90.2 per 100,000 population (95% CI 81.1–100.2). The age-adjusted incidence of FES was 115.7 (95% CI 95.9–139.1) when adjusted to the WHO world populations. Importantly, age-adjusted intracerebral hemorrhage was as much as one third of total FES: 36.9 (95% CI 26.1–51.0).
We found a considerable proportion of FES in Vietnam to be attributable to intracerebral hemorrhage, which is as high or exceeding levels seen in high-income countries. A high prevalence of improperly treated hypertension in Vietnam may underlie the high prevalence of intracerebral hemorrhagic stroke in this population.
Stroke is the second leading cause of death and third leading cause of loss of disability adjusted life years (DALYs) globally and is estimated to be rapidly increasing in low- and middle-income countries (LMICs) [
Comparing stroke incidence in different parts of the world is complex and standardized methods are needed [
Stroke is ranked as the number one cause of loss of DALYs in Southeast Asia [
We conducted the present study with the objective of estimating the population-based incidence of age-, sex- and subtype-specific FES in Vietnam by utilizing our previously established, large-scale, community-based field site in Nha Trang city, central Vietnam.
The current study was conducted in Nha Trang, the capital city of Khanh Hoa Province in South-central Vietnam. The city comprises 19 urban and 8 suburban communes, with a total population of 392,279 in 2009. The Khanh Hoa General Hospital (KHGH) is located in the center of Nha Trang and provides primary to tertiary care for residents. The hospital has an 800-bed capacity, being equipped with two CT scanners and one MRI scanner. KHGH served as the sole provider of hospital acute admission care in the city at the time of study. All admissions in KHGH were recorded in a computerized database with International Classification of Diseases, 10th revision (ICD-10) coding along with age, gender, date of admission, discharge status, and address codes.
We conducted a hospital-based retrospective study, targeting all stroke cases hospitalized at KHGH from January 2009 through to December 2011 (36 months). Eligible cases were identified from the hospital admission database, based on the criteria of ICD-10 code of I60-69 and residing in Nha Trang. To verify the diagnosis of subtype specific FES, 190 medical charts meeting the ICD-10 code criteria were randomly selected and reviewed by a study clinician and an independent neurologist. A standardized form was used to collect demographic information, history of stroke, external injury, hypertension, diabetes mellitus, neurological signs, stroke subtype diagnosis, performing time and remarks of brain CT/ MRI, and status at discharge.
Stroke was defined according to the WHO clinical definition, as a focal (or at times global) neurological impairment of sudden onset, and lasting more than 24 hours (or leading to death), and of presumed vascular origin [
Population-based incidence rates of age- and subtype-specific FES were estimated as follows. Firstly, we calculated positive predictive values (PPVs) of true FES subtype for each ICD-10-coded stroke (I60-69) as a similar approach was applied in previous studies [
Secondly, we estimated the annual number of age-, sex-specific FES cases admitted to KHGH. Out of all the discharge summaries in KHGH, which were assigned to an ICD-10 diagnosis, we counted all ICD-10-coded stroke cases during the three year study period and multiplied the number of cases for each ICD-10-code by the PPV of each ICD-10-code for the targeted FES subtype. The annual number of each FES subtype was estimated by summing up all targeted FES subtypes, including miscoded cases classified elsewhere; then divided by three to obtain the annual incidence.
Thirdly, based on the assumption that all FES cases in Nha Trang city were admitted to KHGH, the age-, sex- and subtype-specific FES incidence rates were calculated by dividing the estimated annual incidence by the number of the relevant population in the city in a certain age group. To compare our estimated incidence with other countries, direct age standardizations were performed using two standard populations: the Vietnamese population in 2009 according to the national census [
Medical chart review revealed 75 FES and 19 recurrent stroke cases among the randomly selected 190 case charts with ICD-10 coding of I60-69. Of the FES cases, 38 (50.7%) and 25 (33.3%) cases were ischemic stroke and intracerebral hemorrhage, respectively. There were 2 (2.7%) cases of subarachnoid hemorrhage. 65 (87%) cases had CT/MRI results but 10 cases (13.3%) were categorized as undetermined subtype due to lack of brain CT/MRI findings. The remaining non-stroke cases were ascertained to be due to the following diseases: headache (n = 51), TIA (n = 12), dizziness (n = 10), subdural hematoma (n = 3), pneumonia (n = 3), brain tumor (n = 2), cardiopulmonary arrest (n = 1), epilepsy (n = 1), hypoglycemia (n = 1), alcohol poisoning (n = 1), hypertension (n = 1), syncope (n = 1), traffic accident (n = 1), and undiagnosed (n = 8).
Characteristics of the subtype specific FES cases are summarized in
Mean ± standard deviation or n (%) are shown; age, admission period of subarachnoid hemorrhage show individual values.
All first-ever stroke (N = 75) | Stroke subtype | |||||
---|---|---|---|---|---|---|
Variables | Ischemic stroke (N = 38) | Intracerebral hemorrhage (N = 25) | Subarachnoid hemorrhage (N = 2) | Undetermined (N = 10) | ||
Age, years | 63 ± 13.6 | 64.8 ± 11.4 | 60.6 ± 17.1 | 57, 63 | 62.9 ± 13 | 0.141 |
Men | 34 (45.3) | 17 (44.7) | 13 (52) | 2 (100) | 2 (20) | 0.572 |
Referred from clinics before admission | 8 (10.7) | 5 (13.2) | 0 | 0 | 3 (30) | 0.071 |
Medical insurance | 40 (53.3) | 21 (55.3) | 13 (52) | 1 (50) | 5 (50) | 0.799 |
Hospital admission fee, USD | 195 | 193 | 260 | 121 | 84 | 0.174 |
Individual payment, USD | 97 | 84 | 143 | 48 | 58 | 0.115 |
Past medical history | ||||||
Hypertension | 55 (73.3) | 29 (76.3) | 17 (68) | 0 | 9 (90) | 0.467 |
Diabetes mellitus | 11 (14.7) | 8 (21.1) | 2 (8) | 0 | 1 (10) | 0.165 |
Dyslipidemia | 1 (1.3) | 1 (2.6) | 0 | 0 | 0 | 0.603 |
Admission period | 8.9 ± 6.5 | 9 ± 6 | 8.4 ± 7.8 | 3, 36 | 9.8 ± 5 | 0.427 |
Fatality | 13 (17.3) | 2 (5.2) | 11 (44) | 0 | 0 | <0.001 |
The PPV of each ICD-10-coded stroke subtype was calculated (
FES indicates first-ever stroke.
ICD-10 code | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Total | I60 (Subarachnoid hemorrhage) | I61 (Intracerebral hemorrhage) | I62 (Other nontraumatic intracranial hemorrhage: subdural hemorrhage etc.) | I63 (Cerebral infarction; ischemic stroke) | I64 (Stroke, not specified as hemorrhage or infarction: undetermined stroke) | I65 (Occlusion and stenosis of precerebral arteries) | I66 (Occlusion and stenosis of cerebral arteries) | I67 (Other cerebrovascular diseases: cerebral aneurysm etc.) | I68 (Cerebral amyloid angiopathy) | I69 (Sequelae of cerebrovascular disease) | |
Reviewed cases (N) | 190 | 1 | 1 | 1 | 3 | 0 | |||||
Ischemic stroke | 38 | 0 | 0 | 0 | 0 | 0 | 0 | ||||
Intracerebral hemorrhage | 25 | 0 | 0 | 0 | 0 | 0 | 0 | ||||
Subarachnoid hemorrhage | 2 | 0 | 0 | 0 | 0 | 0 | 0 | ||||
Undetermined stroke | 10 | 0 | 0 | 0 | 0 | 0 | 0 | ||||
Ischemic stroke | - | 0.033 | - | 0.609 | 0.214 | - | - | - | - | - | |
Intracerebral hemorrhage | - | 0.633 | - | 0.022 | 0.071 | - | - | 0.030 | - | - | |
Subarachnoid hemorrhage | 0.633 |
0.033 | - | - | 0.024 | - | - | - | - | - | |
Undetermined stroke | - | - | - | 0.087 | 0.143 | - | - | - | - | - |
* The PPV of I61 (0.633) was assigned.
According to the ICD-10-code database, a total of 4,344 stroke cases were admitted to KHGH during the 3 years of study period. Among them, 2,693 (62%) were residents of Nha Trang thus eligible for the current analysis. The age-, sex- and subtype-specific distribution of ICD-10-coded stroke cases admitted to KHGH are shown in
Estimated number of annual FES cases for each subtype were calculated by multiplying the total number of age-, sex- and subtype-specific ICD-10-coded cases by the PPV then divided by three years (
The crude annual incidence rate of total FES was 90.2 per 100,000 population (95% CI 81.1–100.2) (
Total population (N) | Ischemic stroke | Intracerebral hemorrhage | Subarachnoid hemorrhage | Undetermined stroke subtype | Total stroke | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Estimated number of cases | Incidence rate (95% CI) | Estimated number of cases | Incidence rate (95% CI) | Estimated number of cases | Incidence rate (95% CI) | Estimated number of cases | Incidence rate (95% CI) | Estimated number of cases | Incidence rate (95% CI) | ||
Male | |||||||||||
Age group, years | |||||||||||
<15 | 46,319 | 0.1 | 0 | 0.7 | 2.2 (0.1–12) | 0.0 | 0 | 0.0 | 0 | 0.9 | 2 (0.1–12) |
15–24 | 37,574 | 0.2 | 0 | 0.8 | 2.7 (0.1–14.8) | 0.2 | 0 | 0.0 | 0 | 1.3 | 2.7 (0.1–14.8) |
25–34 | 32,911 | 0.1 | 0 | 0.9 | 3.0 (0.1–16.9) | 0.0 | 0 | 0.0 | 0 | 1.1 | 3.0 (0.1–16.9) |
35–44 | 32,715 | 5.2 | 15.3 (5–35.7) | 11.3 | 33.6 (16.8–60.2) | 0.8 | 3.1 (0.1–17) | 1.1 | 3.1 (0.1–17) | 18.4 | 55.0 (32.6–87) |
45–54 | 22,081 | 18.7 | 86.1 (51.8–134.4) | 16.0 | 72.5 (41.4–117.7) | 1.6 | 9.1 (1.1–32.7) | 5.0 | 22.6 (7.4–52.8) | 41.3 | 185.7 (133.3–251.9) |
55–64 | 9,136 | 21.3 | 229.9 (142.3–351.4) | 15.3 | 164.2 (91.9–270.8) | 1.6 | 21.9 (2.7–79.1) | 5.0 | 54.7 (17.8–127.7) | 43.2 | 470.7 (340.6–634) |
65–74 | 4,910 | 23.8 | 488.8 (313.2–727.3) | 12.2 | 244.4 (126.3–426.9) | 0.9 | 20.4 (0.5–113.5) | 5.1 | 101.8 (33.1–237.6) | 42.1 | 855.4 (616.5–1156.3) |
75–84 | 3,373 | 23.5 | 711.5 (455.9–1058.7) | 10.4 | 296.5 (142.2–545.2) | 0.8 | 29.7 (0.8–165.2) | 5.2 | 148.2 (48.1–345.9) | 40.0 | 1185.9 (847.2–1614.8) |
≥85 | 718 | 6.2 | 835.7 (306.7–1818.9) | 2.2 | 278.6 (33.7–1006.2) | 0.3 | 0 | 1.8 | 278.6 (33.7–1006.2) | 10.5 | 1532.0 (764.8–2741.2) |
Total | 1,89,737 | 99.2 | 52.2 (42.4–63.5) | 69.8 | 36.9 (28.8–46.6) | 6.4 | 3.2 (1.2–6.9) | 23.4 | 12.1 (7.7–18.2) | 198.7 | 104.9 (90.8–120.5) |
Female | |||||||||||
Age group, years | |||||||||||
<15 | 42,441 | 0.2 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.2 | 0 |
15–24 | 42,400 | 0.4 | 0 | 1.4 | 2.4 (0.1–13.1) | 0.0 | 0 | 0.1 | 0 | 1.9 | 4.7 (0.6–17) |
25–34 | 35,128 | 1.0 | 2.9 (0.1–15.9) | 1.3 | 2.9 (0.1–15.9) | 0.0 | 0 | 0.3 | 0 | 2.7 | 8.5 (1.8–25) |
35–44 | 33,013 | 3.5 | 9.1 (1.9–26.6) | 3.5 | 12.1 (3.3–31) | 0.2 | 0 | 1.0 | 3.0 (0.1–16.9) | 8.1 | 24.2 (10.5–47.8) |
45–54 | 23,833 | 7.5 | 33.6 (14.5–66.1) | 7.1 | 29.4 (11.8–60.5) | 0.5 | 0 | 2.0 | 8.4 (1–30.3) | 17.1 | 71.3 (41.6–114.2) |
55–64 | 11,773 | 16.1 | 135.9 (77.7–220.7) | 9.7 | 84.9 (40.7–156.2) | 0.8 | 8.5 (0.2–47.3) | 4.1 | 34.0 (9.3–87) | 30.7 | 263.3 (178.9–373.8) |
65–74 | 7,871 | 22.4 | 279.5 (175.2–423.2) | 9.8 | 127.1 (60.9–233.7) | 0.8 | 12.7 (0.3–70.8) | 5.2 | 63.5 (20.6–148.2) | 38.3 | 482.8 (341.7–662.7) |
75–84 | 4,717 | 26.8 | 572.4 (377.2–832.8) | 10.3 | 212.0 (101.7–389.9) | 1.2 | 21.2 (0.5–118.1) | 6.7 | 148.4 (59.7–305.8) | 44.9 | 954.0 (695.9–1276.5) |
≥85 | 1,366 | 6.0 | 439.2 (161.2–956) | 3.7 | 292.8 (79.8–749.8) | 0.3 | 0 | 1.7 | 146.4 (17.7–528.9) | 11.7 | 878.5 (453.9–1534.5) |
Total | 2,02,542 | 84.0 | 41.5 (33.1–51.4) | 47.0 | 23.2 (17.1–30.9) | 3.9 | 2.0 (0.5–5.1) | 20.9 | 10.4 (6.4–15.9) | 155.7 | 77.0 (65.4–90.1) |
Male and Female | |||||||||||
Age group, years | |||||||||||
<15 | 88,760 | 0.3 | 0 | 0.7 | 1.1 (0–6.3) | 0.0 | 0 | 0.1 | 0 | 1.1 | 1 (0–6.3) |
15–24 | 79,974 | 0.7 | 1.3 (0–7) | 2.2 | 2.5 (0.3–9) | 0.3 | 0 | 0.1 | 0 | 3.2 | 3.8 (0.8–11) |
25–34 | 68,039 | 1.2 | 1.5 (0–8.2) | 2.2 | 2.9 (0.4–10.6) | 0.1 | 0 | 0.3 | 0 | 3.8 | 5.9 (1.6–15.1) |
35–44 | 65,728 | 8.6 | 13.7 (6.3–26) | 14.8 | 22.8 (12.8–37.6) | 1.0 | 1.5 (0–8.5) | 2.0 | 3.0 (0.4–11) | 26.5 | 41.1 (27.1–59.8) |
45–54 | 45,914 | 26.2 | 56.6 (37–83) | 23.2 | 50.1 (31.8–75.2) | 2.1 | 4.4 (0.5–15.7) | 6.9 | 15.3 (6.1–31.4) | 58.4 | 126.3 (95.9–163.3) |
55–64 | 20,909 | 37.4 | 177.0 (124.6–243.9) | 25.1 | 119.6 (77.4–176.5) | 2.3 | 9.6 (1.2–34.6) | 9.1 | 43.0 (19.7–81.7) | 73.9 | 353.9 (277.9–444.3) |
65–74 | 12,781 | 46.3 | 359.9 (263.5–480.1) | 22.0 | 172.1 (107.9–260.6) | 1.7 | 15.7 (1.9–56.5) | 10.4 | 78.2 (37.5–143.9) | 80.4 | 625.9 (496.3–779) |
75–84 | 8,090 | 50.3 | 618.1 (458.7–814.8) | 20.7 | 259.6 (160.7–396.8) | 2.0 | 24.7 (3–89.3) | 11.9 | 148.3 (76.6–259.1) | 84.9 | 1050.7 (839.3–1299.2) |
≥85 | 2,084 | 12.2 | 575.8 (297.5–1005.8) | 6.0 | 287.9 (105.7–626.7) | 0.6 | 48.0 (1.2–267.4) | 3.5 | 191.9 (52.3–491.4) | 22.3 | 1055.7 (661.6–1598.3) |
Total | 3,92,279 | 183.1 | 46.7 (40.1–53.9) | 116.8 | 29.8 (24.7–35.8) | 10.2 | 2.6 (1.2–4.7) | 44.3 | 11.2 (8.2–15.1) | 354.5 | 90.2 (81.1–100.2) |
Age-adjusted by Vietnam |
49.6 (37.1–65.9) | 31.1 (21.1–44) | 2.7 (0.6–8.8) | 12.1 (6.2–21) | 95.7 (77.8–117.2) | ||||||
Age-adjusted by WHO world |
60.7 (46.7–78.4) | 36.9 (26.1–51) | 3.2 (0.6–8.8) | 14.6 (8.4–24.7) | 115.7 (95.9–139.1) |
*2009 Vietnam national census.
**WHO world standard.
Ischemic stroke was the most common subtype but it is noteworthy that intracerebral hemorrhage constituted as much as one third of total stroke in this population. When the subtype-specific FES incidence rates were calculated, the crude incidence of ischemic stroke was only 1.57 fold greater than hemorrhagic: 46.7 (95% CI 40.1–53.9) vs 29.8 (95% CI 24.7–35.8), respectively. The incidence of FES was higher in men than in women regardless of pathological type. However total number of women admitted to KHGH with ICD-10-coded stroke was higher than men. This discrepancy was mainly attributed to the considerably higher number of women admitted with ICD-10-I67 (
This is the first population-based study in southeast Asia, documenting age-, sex- and subtype-specific stroke incidence rates. We found a considerable proportion of FES in central Vietnam to be attribute to intracerebral hemorrhage and age-adjusted incidence rate of intracerebral hemorrhage at 36.9 is the highest reported since 2000, including other LMICs (
NR = not reported. The direct age standardizations were performed using WHO world standard populations.
Study site | Study duration (year) | Age-adjusted incidence of first-ever stroke per year/100,000 population (95% CI) | Age-adjusted incidence of ischemic stroke per year/100,000 population (95% CI) | Age-adjusted incidence of intracerebral hemorrhage per year/100,000 population (95% CI) | Age-adjusted incidence of subarachnoid hemorrhage per year/100,000 population (95% CI) | Age-adjusted incidence of undetermined stroke per year/100,000 population (95% CI) |
---|---|---|---|---|---|---|
Valley d' Aosta, Italy(5) | 2004–2005 | 97 (80–114) | 75 (60–90) | 10 (5–15) | 5 (1–9) | 8 (3–13) |
Barbados, Barbados (6) | 2001–2002 | 102.8 (84.1–124.9) |
88.3 (70.6–108.4) |
13.3 (6.9–22.2) |
2.8 (0.6–8.8) |
3.6 (1.1–10.2) |
Oxfordshire, UK(7) | 2002–2004 | 73 (64–83) | NR | NR | NR | NR |
Auckland, New Zealand(8,9) | 2002–2003 | 102.9 (84.1–124.9) |
75.2 (59–94) |
13.2 (6.9–22.2) |
6.9 (2.8–14.4) |
7.6 (3.5–15.8) |
Iquique, Chile(10) | 2000–2002 | 108.2 (95.8–120.6) | 63.9 (49.3–81.7) |
22.2 (13.8–33.3) |
NR | NR |
Tbilisi, Georgia(11) | 2000–2003 | 116.1 (95.9–139.1) |
60.3 (45.8–77.2) |
29.3 (19.4–41.7) |
14.1 (7.7–23.5) |
12.5 (6.9–22.2) |
Matao, Brazil(12) | 2003–2004 | 137 (112–166.4) | 122.9 (102.2–146.8) |
20.0 (13–32.1) |
NR | NR |
Trivandrum, India(13) | 2005 | 135 (123–146) | 74.8 (66.3–83.2) | 10.1 (7–13.2) | 4.2 (2.2–6.1) | NR |
Nha Trang, Vietnam | 2009–2011 | 115.7 (95.9–139.1) | 60.7 (46.7–78.4) | 36.9 (26.1–51) | 3.2 (0.6–8.8) | 3.2 (0.6–8.8) |
† Calcurated by the author, based on the reports.
¶ Calcurated by the author, based on the reports. Incidence rate aged <15 assumed zero.
It has been reported that the incidence of hemorrhagic stroke is more strongly associated with blood pressure than ischemic stroke [
We predict a dramatic increase in the number of stroke cases as the Vietnamese population ages. Life expectancy at birth increased rapidly from 6.1 to 8.4 years for men, and from 7.3 to 8.9 years in women for two decades in Vietnam, Lao, and Cambodia [
e estimated the predicted o f fr of stroke patients in 2030 i PPV of I60 to predict subarachnoid hemorrhage because PPVs to f f
e estimated the predicted o f fr of stroke patients in 2030 i PPV of I60 to predict subarachnoid hemorrhage because PPVs to f f
Potential limitations of this study include the possible underestimation of the true FES incidence due to ascertainment from a single hospital (and not including private clinics) and limited to those with hospital ICD-10-coded stroke which could result in missed cases. However, in this study setting, there was no other hospital with admission facility for stroke patients, and also we assumed that economic barriers to hospital admission was low in Vietnam, because it used to be a socialist country and the majority of residents hold health insurance [
The age-adjusted incidence rate of FES in central Vietnam is compatible with previous reports showing stroke incidence rates in LMICs as high or exceeding levels seen in high-income countries. Our findings also highlight the relatively high proportion of intracerebral hemorrhage, which is important to consider screening and preventive strategies in Vietnam.
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This study was a collaborative research effort between Nagasaki University (Japan), National Institute of Hygiene and Epidemiology (Vietnam), Khanh Hoa Provincial Public Health Service (Vietnam), and KHGH (Vietnam). We thank those who cooperated in this study in both Vietnam and Japan.
disability adjusted life years
low- and middle- income countries
first-ever stroke
Khanh Hoa General Hospital
International Classification of Diseases, 10th revision
transient ischemic attack
positive predictive values
confidence intervals
standard Deviation