Williams et al [8
] estimated that there were 750,000 first-ever or recurrent strokes in 1995. We conservatively estimate that there were 783,000 first-ever or recurrent strokes in 1996. The 33,000 (4.4%) increase in first-ever or recurrent strokes may be due to chance, but it is probably due to the population gain (262,803,000 in 1995 versus 265,229,000 in 1996, a 0.9% increase), and the increase in aging (≥ 65 years old) population from 1995 to 1996 (33,619,000 in 1995 versus 33,957,000 in 1996, a 1.0% increase).[16
] The aging population effect is more pronounced in the group aged 75+ years who are at greater risk of stroke (14,863,000 in 1995 versus 15,266,000 in 1996, a 2.7% increase).[16
] We also estimate that American hospitals charged $12.4 billion for stroke treatment and management during 1996, which translates to a society cost of approximately $7 billion.
It is worthwhile to notice the remarkable consistency in stroke patient characteristics between 1995 and 1996, as shown in Table . The length of stay, however, was shorter in 1996 than in 1995 for stroke patients, although the total charge was higher in 1996 than in 1995. It may be due to a combination of inflation and inpatient healthcare practice changes or healthcare reimbursement regulation changes.
The present study may be associated with several limitations. First, the validity of conclusions drawn from analyses of large administrative databases depends on the accuracy of case-defining diagnostic codes. Therefore, the validity of the present study is highly dependent on the accuracy of the positive predictive values of the ICD-9-CM codes, which has been addressed.[8
The impact of the uncertainty in the PPV pooled estimates was examined by constructing a 95% confidence interval around the number of hospital strokes. The bounds of this confidence interval were tight (688,000, 737,000), indicating that the point estimate had reasonable precision.
Another limitation of the present study is the lack of documented information on the rate of nonhospital stroke. Additional data are needed to produce a more reliable estimate of the proportion of strokes without hospitalization. By intentionally choosing a low percentage, we were confident that our estimate of the total annual stroke burden was not inflated. We used sensitivity analyses to illustrate the potential impact of a different true percentage. In addition, race-specific information was not available, which limited our ability to adjust for race.
The methodology used in the present study was the same as the one used in Williams et al, [8
] but different from other studies published on the incidence, occurrence and characteristics of stroke. All those studies used state-of-the-art stroke registries based in relatively small geographical areas (Framingham, Massachusetts; Rochester, Minnesota; Rochester, New York; Northern Manhattan, New York; Greater Cincinnati/Northern Kentucky). Our approach might have slightly reduced internal validity, but it should have far greater external validity, although this might be somewhat compromised by the reduced internal validity.
In summary, this study supports the findings of Broderick et al [5
] and Williams et al [8
] by conservatively estimating that there are approximately three-quarters of a million strokes each year. In addition, we observed that there is a slight increase, although not statistically significant, in occurrences of stroke from 1995 to 1996. This is likely due to a combination of the population gain and the aging of the population from 1995 to 1996.
In conclusion, stroke is a significant problem in the United States. The importance of preventive measures for a disease that has identifiable and modifiable risk factors must be emphasized. The reduction of morbidity and mortality among stroke patients must remain a public health priority.