WWW-publications from the WHO MONICA Project
October 2000
Markku Mähönen1, Hanna Tolonen1 and Kari Kuulasmaa1 for the WHO MONICA Project2
1 MONICA Data Centre, National Public Health Institute, Helsinki, Finland
2 Annex: Sites and key personnel of the WHO MONICA
Project
This document updates parts of unpublished reports:
Thanks are due to Birgitta Stegmayr, Per Thorvaldsen, Alun Evans and Hugh Tunstall-Pedoe for thoughtful comments.
The MONICA Centres are funded predominantly by regional and national governments, research councils, and research charities. Coordination is the responsibility of the World Health Organization (WHO), assisted by local fund raising for congresses and workshops. WHO also supports the MONICA Data Centre (MDC) in Helsinki. Not covered by this general description is the ongoing generous support of the MDC by the National Public Health Institute of Finland, and a contribution to WHO from the National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA for support of the MDC and the Quality Control Centre for Event Registration in Dundee. The completion of the MONICA Project is generously assisted through a Concerted Action Grant from the European Community. Likewise appreciated are grants from ASTRA Hässle AB, Sweden, Hoechst AG, Germany, Hoffmann-La Roche AG, Switzerland, the Institut de Recherches Internationales Servier (IRIS), France, and Merck & Co. Inc., New Jersey, USA, to support data analysis and preparation of publications.
This data book provides detailed descriptive statistics for each MONICA population on the data of the MONICA stroke event registers for the years 1982-1995. The data book consists of summary tables of annual data of the most important data items for age group 35-64 and for age group 65-74.
The report is based on the data which the MONICA Data Centre (MDC) has received from the MONICA Collaborating Centres (MCCs) on stroke events (Form 03)(1), population statistics (Form A) and mortality statistics (Forms C and E)(2).
In the specifications of the calculations for this data book the names of the data items of the Core Data Transfer Format-Stroke Events (1) have been used. The terminology used is this report follows that developed for MONICA event registration in the MONICA Manual (1), with later refinements in the collaborative publications (3, 4).
The report considers the Reporting Unit Aggregates (RUAs) which are foreseen as potential candidates for units of analysis of the MONICA stroke event data. The RUAs, their abbreviations and Reporting Units (RU) are listed in Table 1. Different combinations of RUs may be used for analyses concerning stroke events only and other for analyses involving both stroke event and risk factor data. Therefore, some RUAs have several versions distinguished by suffix a or b. The reason for the distinction is that some RUs of some RUAs were not included in every risk factor survey or the different RUs had different stroke registration periods. Therefore, in RUS-MOI, RUS-NOC and the RUAs of MONICA East Germany (GER-EGE,GER-HAC, GER-KMS, GER-RDM) there is an overlap of RUs included in the RUAs concerned. Altogether 25 RUAs are considered (Table 1).
The calendar years included in this report from each population are shown in Table 1.
For the age group 65-74 years data from the RUAs CHN-BEI, GER-HAC, GER-RDM, HUN-BUD, HUN-PEC, RUS-NOCa and RUS-NOCb were excluded because the data were clearly incomplete (5).
Individual records have not been included in the analysis if:
Otherwise, all data available in MDC were used in the analysis. The number of events excluded from the analysis, and the reasons for exclusion, are shown in Table 2.
Standardized methods for data collection were defined for the MONICA Project, and particular attention was paid on training of the personnel involved in data collection and processing and on quality control. The quality of the event registration data and the demographic data are reported in separate quality assessment reports (5,6). No data were excluded from this data book because of problems in the quality. Therefore, the quality assessment reports should be consulted before using the data presented.
| Survival status: | Description | SURVIV |
|---|---|---|
| Fatal and non-fatal events: | Survival status not considered | any |
| Fatal events: | Dead at 28 days after onset | 2 |
| Non-fatal events: | Alive at 28 days after onset, or insufficient data for survival status | 1 or 9 |
| Order of event | Description | PRESTR |
|---|---|---|
| First events | No previous stroke | 3 or 4 |
| Recurrent events | Previous stroke | 1 or 2 |
| Indeterminate events | Unknown status with respect to previous stroke | 9 |
First events, recurrent events or indeterminate events are considered in Tables and text only when specifically mentioned. Otherwise, all events are included regardless of the previous history.
| Diagnostic category | Abbreviation | DIACAT | SURVIV |
|---|---|---|---|
| Fatal stroke | F1+F5+F9 | 1 or 5 or 9 | 2 |
| Definite fatal stroke | F1+F5 | 1 or 5 | 2 |
| Unclassifiable fatal event | F9 | 9 | 2 |
| Non-fatal stroke | NF1+NF5+NF9 | 1 or 5 or 9 | 1 or 9 |
| Definite non-fatal stroke | NF1+NF5 | 1 or 5 | 1 or 9 |
| Unclassifiable non-fatal event | NF9 | 9 | |
| Definition 1 | Def 1 | 1 or 5 or 9 | any |
| Definition 2 | Def 2 | 1 or 5 | any |
All original codes for type of stroke given in each MCC by their local stroke register team were checked using the algorithm:
| Original type | Condition | Correct type |
|---|---|---|
| ICD8: 430 ICD9: 430 |
CT or NECROPSY or (ANGIO and LP) performed | 430 |
| otherwise | 436 | |
| ICD8: 431 ICD9: 431 |
CT or NECROPSY performed | 431 |
| otherwise | 436 | |
| ICD9: 432 | (This coding is illegal) | 436 |
| ICD8: 432 ICD9: 433 |
NECROPSY or ANGIO performed | 433 |
| CT performed but not NECROPSY or ANGIO | 434 | |
| otherwise | 436 | |
| ICD8: 433 or 434 ICD9: 434 |
CT or NECROPSY or ANGIO performed | 434 |
| otherwise | 436 | |
| ICD8: 436 ICD9: 436 |
CT performed but not NECROPSY | 434 |
| otherwise | 436 |
All data on stroke subtypes presented in this data book are corrected according to this algorithm. If the proportion of CT-scan and/or necropsy performed in fatal definite stroke events (F1 + F5) or the proportion of CT-scan performed in non-fatal definite stroke events (NF1 + NF5) is less than 70%, the proportions of the different type of stroke are not reported in this data book.
The ninth revision of ICD was used presenting the data in this data-book. Data from the MCCs using ICD-8 were transferred to ICD-9 using the rule:
| ICD-8 | ICD-9 | |
|---|---|---|
| Subarachnoid haemorrhage | 430 | 430 |
| Intracerebral haemorrhage | 431 | 431 |
| Brain infarction | 432-434 | 433-434 |
| Acute but ill-defined cerebrovascular disease | 436 | 436 |
The age-standardized event rates were calculated using the "World standard population"(7), with the following weights:
| Age group | 35-39 | 40-44 | 45-49 | 50-54 | 55-59 | 60-64 | 65-69 | 70-74 |
|---|---|---|---|---|---|---|---|---|
| Weight | 6 | 6 | 6 | 5 | 4 | 4 | 3 | 2 |
When reporting first events only, the years with availability of data on previous stroke less than 70% were not included.
The 95% confidence intervals for event rates were calculated using the relationship between the Poisson and chi-squared approximation to define the confidence intervals for weighted sums of Poisson parameters (8).
Case-fatality was calculated as the proportion of fatal events in fatal and non-fatal events. Case-fatality for the age group 35-74 years was age-standardized using the following weights:
| Age group | 35-44 | 45-54 | 55-64 | 65-74 |
|---|---|---|---|---|
| Weight | 1 | 3 | 7 | 12 |
These weights were derived by looking at the overall number of fatal and non-fatal coronary and stroke events in the MONICA data in MDC. If the denominator of the youngest age group was zero, the two youngest age groups were combined, using weight 4. (This occurred occasionally for women.) If the denominator of one of the older age groups was zero, no age standardization was used. For case-fatality the 95% confidence intervals were calculated in the conventional manner using the normal approximation of the binomial distribution (9). The 10-year age-specific case-fatality was only printed in the tables if the number of fatal events was at least 10.
When reporting case-fatality of first stroke events only, the years with the availability of data on previous stroke less than 70% were not included.
Proportions of different stroke subtypes for age group 35-64 years were age-standardized using the same weights as for case-fatality. In nonfatal events stroke subtypes were calculated only if the proportion of definite (NF1+NF5) nonfatal stroke events examined with CT scan was 70% or more. In fatal events stroke subtypes were calculated only if the proportion of definite (F1+F5) fatal stroke events autopsied or examined with CT scan was 70% or more.
Tables 3.1, 3.2, 3.3 and 3.4 present the proportions of first ever, recurrent and indeterminate fatal and nonfatal stroke events (F1+F5+F9) in age groups 35-64 years and 65-74 years.
In fatal events the proportion of indeterminate events was over 30% in the age group 35-64 years in (Table 3.1):
In nonfatal events the proportion of indeterminate events was above 10% in age group 35-64 years in (Table 3.2):
In fatal events the proportion of indeterminate events was over 30% in the age group 65-74 years in (Table 3.3) :
In nonfatal events the proportion of indeterminate events was over 10% in age group 65-74 years in (Table 3.4):
In nonfatal events the availability of data on previous stroke was uniformly high. In fatal events there was a high proportion of indeterminate stroke events in some RUAs, which should be considered when data on stroke incidence are analyzed.
Age-standardized proportions of the different stroke subtypes (the proportions were calculated only if the proportion of events examined with CT was over 70%, see Section 4.2) and rates for definite nonfatal strokes for age group 35-64 years are presented in Table 4.1. Only GER-RHN, ITA-FRI, SWE-GOT and SWE-NSW could be tabulated for all years. During the later study period time also CHN-BEI, DEN-GLO, FIN-KUO and FIN-TUL could be tabulated.
Age-standardized proportions of the different stroke subtypes and rates for definite fatal strokes for age group 35-64 years are presented in Table 4.2. Age-standardized proportions of different fatal stroke subtypes could not be tabulated for the following years (the proportion of autopsied or examined with CT scan was below 70%, see Section 4.2): CHN-BEI (1984-1993); FIN-KUO (1984); FIN-NKA (1982-1989); GER-EGEa (1985-1988); GER-EGEb (1985-1990); GER-HAC (1984-1986); GER-KMSb (1985-1989); GER-RDMd (1984-1987); GER-RHN (1984-1986); ITA-FRI (1985, 1987-1988); LTU-KAU (1994); POL-WAR (1984-1994); RUS-NOCa (1987, 1991, 1993) RUS-NOCb (1987, 1989, 1993); RUS-NOI (1986, 1993); and YUG-NOS (1983-1995).
Age standardized proportions for stroke subtypes could only seldom be tabulated in the age group 65-74 years (Tables 4.3 and 4.4) since the proportion of events examined with CT and/or autopsied was most often below 70% (see Section 4.2).
Tables 5.1 and 5.2 present event rates of stroke in men and women aged 35-64 and 65-74, both for definition 1 and definition 2. Tables 6.1 and 6.2 present the events rates for first ever strokes. Tables 7.1 and 7.2 present age-standardized mortality from stroke. Tables 8.1 and 8.2 present the case-fatality of all strokes. Tables 9.1 and 9.2 present the case-fatality of first ever strokes.