CORRESPONDENCE

Let's Leave the Date Out of the Name of the Standard Population

Thomas H. Taylor, Hoda Anton-Culver

Affiliation of authors: Epidemiology Division, Department of Medicine, University of California, Irvine.

Correspondence to: Hoda Anton-Culver, Ph.D., Epidemiology Division, Department of Medicine, University of California, Irvine, 224 Irvine Hall, Irvine, CA 92697-7550 (e-mail: hantoncu{at}uci.edu).

Ironically, as we are beginning to win the war on cancer, we will soon publish age-standardized incidence and mortality rates that are mostly higher than what the public has seen for many years. This letter is in reference to the adoption by the Department of Health and Human Services of the projected population of the year 2000 for use in age standardization (1). True, some see the present 1970 standard as outdated (2), but this perception is valid only when age-standardized rates are interpreted as descriptions of absolute risk in specific populations. Age-standardized rates are really appropriate only for comparisons across groups or across time. Arguably, the best descriptions of incidence and mortality in specific populations are age-specific and cumulative rates (3).

The effect of using the new standard population on average-annual, age-standardized incidence rates per 100 000 for several cancer types in Orange County, CA (4), compared with the current SEER1 standard million, is shown in Table 1Go. The table shows appreciable changes in age-standardized incidence rates, wholly attributable to changing the standard population. Under the 2000 standard, the rate of acute lymphocytic leukemia declines because children constitute the bulk of such patients and because children count, proportionately, less in the 2000 standard than in the SEER (1970) standard. However, the underlying risk of disease is constant in Table 1Go. The perception will be that more progress has been made in the prevention of childhood cancers than is really the case.


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Table 1. Average-annual, age-standardized cancer incidence rates, Orange County, CA, 1993–1997, comparing 1970 standard population with 2000 standard population
 
For adult malignancies, the values of the age-standardized rates increase using the 2000 standard population. Whatever public-relations gains are made from the modernization of the age-standardization procedure may be offset by the easier-to-notice "fact" that adult cancer risks are higher than previously thought. For example, Orange County women perceive, correctly, that they are at relatively high risk for breast cancer (5). Therefore, when residents see that the average-annual, age-standardized incidence rate jumps from 113.4 per 100 000 to approximately 135, we expect that many people will become upset. It is impossible to withdraw all of the publications involving the older standard, and people will rush to conclusions. Similar stories are expected for other high-profile malignancies and for those malignancies widely regarded to be fatal (e.g., pancreas).

We are aware of government plans to prepare journalists and others for the new rates, and we applaud the intent to have a common standard population used by, ideally, all who publish health data. But, aside from achieving consistency, there is no technical need to change the standard population (6). We suggest that the new, common standard population be named without reference to the calendar year and be reserved for comparisons across populations or time. Education efforts should encourage the use of age-specific rates to describe cancer in specific populations. In the future, we should avoid expending resources and political capital to accommodate updates of the standard population. Most important, we should promote clarity, rather than confusion, in the public's perception of cancer risks.

NOTES

1 Editor's note: SEER is a set of geographically defined, population-based, central cancer registries in the United States, operated by local nonprofit organizations under contract to the National Cancer Institute (NCI). Registry data are submitted electronically without personal identifiers to the NCI on a biannual basis, and the NCI makes the data available to the public for scientific research. Back

REFERENCES

1 Shalala DE. HHS policy for changing the population standard for age adjusting death rates: memorandum from the Secretary. U.S. Department of Health and Human Services, August 26, 1998.

2 Anderson RN, Rosenberg HM. Report of the second workshop on age adjustment. National Center for Health Statistics. Vital and Health Statistics 1998;4:2.

3 Esteve J, Benhamou E, Raymond L. Statistical methods in cancer research. Vol. IV. Descriptive epidemiology. New York (NY): Oxford University Press; 1994. p. 98.

4 Anton-Culver H, Taylor TH, Bringman D, Rowley K, Cinar P, Leach S, et al. Cancer incidence and mortality in Orange County: 1993–1997. Irvine (CA): Cancer Surveillance Program of Orange County/San Diego—Imperial Organization for Cancer Control, Epidemiology Division, Department of Medicine, University of California, Irvine; 2000. p. 5.

5 Snipes KP. Incidence and mortality of female breast cancer, 1988–1993. In: Morris CR, Wright WE, editors. Breast cancer in California. Sacramento (CA): California Department of Health Services, Cancer Surveillance Section; 1996. p. 12.

6 Feinleib M, Zarate AO, editors. Reconsidering age-adjustment procedures: workshop proceedings. National Center for Health Statistics. Vital and Health Statistics 1992;4:51.



             
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