Technical Notes

Nature and Sources of Data

Provisional drug overdose death counts are based on death records received and processed by the National Center for Health Statistics (NCHS) as of a specified cutoff date. The cutoff date is generally the first Sunday of each month. National provisional estimates include deaths occurring within the 50 states and the District of Columbia. NCHS receives the death records from the state vital registration offices through the Vital Statistics Cooperative Program (VSCP).

The timeliness of provisional mortality surveillance data in the National Vital Statistics System (NVSS) database varies by cause of death and jurisdiction in which the death occurred. The lag time (i.e., the time between when the death occurred and when the data are available for analysis) is longer for drug overdose deaths compared with other causes of death due to the time often needed to investigate these deaths (1). Thus, provisional estimates of drug overdose deaths are reported 6 months after the date of death.

Provisional death counts presented in this data visualization are for “12 month-ending periods,” defined as the number of deaths occurring in the 12 month period ending in the month indicated. For example, the 12 month-ending period in June 2020 would include deaths occurring from July 1, 2019 through June 30, 2020. The 12 month-ending period counts include all seasons of the year and are insensitive to reporting variations by seasonality. These provisional counts of drug overdose deaths and related data quality metrics are provided for public health surveillance and monitoring of emerging trends. Provisional drug overdose death data are often incomplete, and the degree of completeness varies by jurisdiction and 12 month-ending period. Consequently, the numbers of drug overdose deaths are underestimated based on provisional data relative to final data and are subject to random variation.

Cause of Death Classification and Definition of Drug Deaths

Mortality statistics are compiled in accordance with the World Health Organizations (WHO) regulations specifying that WHO member nations classify and code causes of death with the current revision of the International Statistical Classification of Diseases and Related Health Problems (ICD). ICD provides the basic guidance used in virtually all countries to code and classify causes of death. It provides not only disease, injury, and poisoning categories but also the rules used to select the single underlying cause of death for tabulation from the several diagnoses that may be reported on a single death certificate, as well as definitions, tabulation lists, the format of the death certificate, and regulations on use of the classification. Causes of death for data presented on this report were coded according to ICD guidelines described in annual issues of Part 2a of the NCHS Instruction Manual (2). Drug overdose deaths are identified using underlying cause-of-death codes from the Tenth Revision of ICD (ICD–10): X40–X44 (unintentional), X60–X64 (suicide), X85 (homicide), and Y10–Y14 (undetermined).

Selection of Specific Jurisdictions to Report

Provisional counts are presented by the jurisdiction where the decedent resides (e.g. county of residence). Data quality and timeliness for drug overdose deaths vary by reporting jurisdiction. Provisional counts are presented, along with measures of data quality: the percentage of records where the manner of death is listed as “pending investigation”, and a note for specific jurisdictions with historically lower levels of data completeness (where provisional 2019 data were less than 90% complete after 6 months).

Percentage of Records Pending Investigation

Drug overdose deaths often require lengthy investigations, and death certificates may be initially filed with a manner of death “pending investigation” and/or with a preliminary or unknown cause of death. When the percentage of records reported as “pending investigation” is high for a given jurisdiction, the number of drug overdose deaths is likely to be underestimated. Counts of drug overdose deaths may be underestimated to a greater extent in jurisdictions or counties where more records in NVSS are reported as “pending investigation” for the six most recent 12 month-ending periods.

Historical Completeness

The historical percent completeness of provisional data is obtained by dividing the number of death records in the NVSS database for each jurisdiction and county after a 6-month lag for deaths occurring in 2019 by the number of deaths eventually included in the final data files. Counties with historically lower levels of provisional data completeness are flagged with a note to indicate that the data may be incomplete in these areas. However, the completeness of provisional data may change over time, and therefore the degree of underestimation will not be known until data are finalized (typically 11-12 months after the end of the data year).

Differences between Final and Provisional Data

There may be differences between provisional and final data for a given data year (e.g., 2020). Final drug overdose death data published annually through NCHS statistical reports (3) and CDC WONDER undergo additional data quality checks and processing. Provisional counts reported here are subject to change as additional data are received.

Source

NCHS, National Vital Statistics System. Estimates for 2023 are based on provisional data. Estimates for 2020-2022 are based on final data (available from: https://www.cdc.gov/nchs/nvss/mortality_public_use_data.htm).

References

1. Spencer MR, Ahmad F. Timeliness of death certificate data for mortality surveillance and provisional estimates. National Center for Health Statistics. 2016. Available from: https://www.cdc.gov/nchs/data/vsrr/report001.pdf
2. National Vital Statistics System. Instructions for classifying the underlying cause of death. In: NCHS instruction manual; Part 2a. Published annually.
3. Hedegaard H, Miniño AM, Warner M. Drug overdose deaths in the United States, 1999–2018. NCHS Data Brief, no 356. Hyattsville, MD: National Center for Health Statistics. 2020. Available from: https://www.cdc.gov/nchs/products/databriefs/db356.htm

Suggested Citation

Ahmad FB, Anderson RN, Cisewski JA, Rossen LM, Warner M, Sutton P. County-level provisional drug overdose death counts. National Center for Health Statistics. 2024.

Designed by MirLogic Solutions Corp: National Center for Health Statistics.