New Considerations in Analyzing Stroke and Heart Disease Mortality Trends: the Year 2000 Age Standard and the International Statistical Classification of Diseases and Related Health Problems, 10th Revision

Background: Monitoring of trends and patterns of stroke mortality will be of utmost importance in the coming decade. Two innovations in vital statistics may complicate this task and must be brought to the attention of both researchers and readers of research reports: the new Year 2000 Age Standard and the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10).

Summary Of Review: For cerebrovascular diseases, the age-adjusted death rate is 2.4 times higher with the use of the year 2000 standard than with the use of the old 1940 standard. However, if rates for all years are computed with the use of the same age standard, the percent change from 1979 to 1995 is similar according to the 1940 standard (-35.8%) or the year 2000 standard (-34.3%). Another important effect of the change to the year 2000 standard is to reduce black/white differentials in age-adjusted death rates. Major discontinuities are not observed for mortality trends in cerebrovascular disease or heart disease between International Classification of Diseases, Ninth Revision (ICD-9) (1979-1998) and ICD-10 (1999 and following years) classifications.

Conclusions: All data users must exercise caution to specify the age standard used when assessing or presenting age-adjusted rates over time or between groups. The comparability of ICD codes chosen for years before 1999 versus 1999 or following years must be checked to distinguish changes due to coding from true changes in mortality levels.