摘要：The standard terminal age category in disease reporting in the United States has been 85 years and older since the 1940s, but the dramatically increasing share of the US population reaching this age has rendered the single category inadequate for surveillance, research, and analysis. Important age-specific variations in mortality among the oldest old are masked by the continued use of this category. Greater specificity in age-specific data for the oldest old would aid in disease surveillance and etiologic research and broaden awareness and understanding of human longevity. DATA ON DISEASE INCIDENCE and mortality are commonly classified into 5- or 10-year age groups. This practice was established roughly a century ago—when official vital records were uncommon in the United States—because of the tendency for ages to be reported as multiples of 5. 1 This issue still applies to immigrants in the United States from countries that do not rigorously maintain vital records, 2 but it is no longer a concern overall. Still, 5- and 10-year age groups continue to be widely used for reasons of practicality and convenience. At the same time, researchers are increasingly using single-year-of-age data (with every age in years in its own category) in epidemiological studies, particularly pediatric studies. Regardless of how age data are classified and analyzed, the terminal age category is almost always 85 years and older. The use of 85 years and older as the terminal age category became common practice around 1940, as reflected in the vital statistics data published in the annual Vital Records of the United States and the Statistical Abstract of the United States , both published by the US Bureau of the Census. Before then, a 75-years-and-older age group was the most common terminal group. Neither series explicitly remarked upon the shift from 75 years and older to 85 years and older even though both had discussed many other fine points of demographic measurement. Given the steady upward trend in longevity in the United States in the early part of the 20th century, perhaps the US Bureau of the Census saw the decision to redefine the oldest age group as too obvious to require explanation. The upward trend in longevity has continued, and an upward revision to the oldest age group is overdue. In 1940 there were 365000 people 85 years and older in the United States, representing 0.3% of the total population. 3 By 2000, more than 4.2 million (1.5%) Americans were 85 years and older, with 337000 (0.1%) aged 95 years and older, 4 nearly the size of the 85-years-and-older population 60 years earlier. By 2030, the population 100 years and older is projected to reach this level (Figure 1 ▶ ). 3 – 8 Open in a separate window FIGURE 1— Historic and projected populations 85 years and older (a) and 100 years and older (b): United States, 1900–2050. Source. Data are from the US Census Bureau 3 – 5 , 7 , 8 and Siegel and Passel. 6 I have found no evidence of federal agencies presenting disease rates by 2 or more age groups for those aged 85 years and older. Mortality counts, by contrast, have been available for 5-year age groups up to the group of 100 years and older ever since Texas became the last state to officially collect mortality data in the mid-1930s. 1 Cancer incidence data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program have also long been available by single year of age with an upper limit of 115 years. 9 In past decades, these numerator data were not considered especially reliable, but they are now of very high quality, validated with historic census records and Social Security Administration records. 10 The limiting factors in the calculation of rates for subgroups of the traditional terminal category of 85 years and older are the insufficient availability and quality of population data. The US Census Bureau publishes data for these age groups stratified by race, ethnicity, state, and county only in decennial census years. Intercensus and postcensus estimates and projections provide only national-level counts. Dicennial census data overstate the numbers in the oldest age groups, particularly centenarians; although the problem has diminished over time, it remains an issue. 11 The traditional explanation for the problem of overstatement is age exaggeration—the tendency for those in their nineties to add years to their age to reach the esteemed century mark. However, empirical studies have typically found more of a tendency for people to understate their age. 12 The same person might contribute to both patterns, as in the following humorous anecdote, originally published in 1936: In the matter of prolonging human life, science has played no part whatever. Take the history of one Bessie Singletree. . . . On her twenty-seventh birthday Miss Singletree became twenty-four years of age and was married. At thirty-five she was thirty. At forty she was thirty-nine until she was close to fifty. At fifty Bessie was forty; at sixty, fifty-five. At sixty-five she was sixty-eight and on her seventieth birthday everyone said Grandmother Singletree was pretty chipper for an octogenarian. At seventy-five she had her picture in the paper as the oldest woman in the county, aged ninety-three. Ten years later she passed away at the ripe old age of one hundred and nine. 6 (p560) Even when ages are systematically understated overall, the number of centenarians will be exaggerated. To illustrate this, consider 2 age groups, 95 years through 99 years and 100 years and older, and assume that 3% of those aged 95 to 99 years are reported as being 100 years or older (age inflation), 6% of those 100 years or older are reported as being aged 95 to 99 years (age understatement), and that the true ratio of 95- to 99-year-olds to those 100 years or older is 10 to 1. Because there are so many more 95- to 99-year-olds, most of the misclassification will accrue to the 100-years-and-older group even though this group has a lower misclassification rate. This particular example would yield 124 reported centenarians for every 100 actual centenarians. Beyond the misreporting of age, poor estimates of the extremely aged (90 years and older, but especially centenarians) in past censuses have also resulted from systematic data-collection problems. A prominent example is a problem with the physical design of the 1970 US Census questionnaire that led many respondents to unintentionally indicate they were born in the 1860s. 6
