Decreasing mortality from pulmonary embolism in the United States, 1979–1996

David Eugene Lilienfeld


    Abstract
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Background Mortality trends and patterns for pulmonary embolism may yield clues to its aetiology. Previous investigations had identified several mortality contrasts in pulmonary embolism mortality among US residents. These findings had been made in the context of a trend of increasing rates during 1962–1984.

Methods Annual age-specific and age-adjusted pulmonary embolism mortality rates for US residents during 1979–1996 were compiled from the US National Center for Health Statistics web site. These data were analysed for mortality contrasts and trends.

Results For all racial-gender groups, age-adjusted mortality declined throughout the period. The greatest rate of decline was found among black men, followed by (in decreasing order) black women, white men, other men, white women, and other women. In 1996, the previously observed demographic contrasts of blacks experiencing the highest pulmonary embolism mortality, followed by whites and then others, and the male rate being higher than the female one were still present despite this decline. Age-specific mortality from pulmonary embolism in the US during 1996 also mirrored that reported for the 1970s, with mortality increasing during the life span (the risk of death doubling with each decade of life). Specifically, the annual age-adjusted pulmonary embolism mortality rate in 1996 for white men was 2.4 per 100 000 persons; white women, 2.3 per 100 000 persons; black men, 6.0 per 100 000 persons; black women, 4.8 per 100 000 persons; non-black non-white men, 1.0 per 100 000 persons; and non-black non-white women, 0.7 per 100 000 persons.

Conclusions Mortality from pulmonary embolism in the US declined significantly during 1979–1996. Several demographic contrasts, particularly an excess among men, continue to exist.

Keywords Mortality, pulmonary embolism, cardiovascular disease, pulmonary circulation

Accepted 18 November 1999


    Introduction
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Pulmonary embolism is a common clinical condition with considerable associated morbidity and mortality. In 1982, Bell estimated that in excess of 600 000 cases occur annually in the US.1 In spite of this considerable clinical burden, pulmonary embolism remains a disorder for which we have incomplete epidemiological knowledge. In 1990, Lilienfeld et al.2 and Soskolne et al.3 reported increases in pulmonary embolism mortality from the early 1960s through the middle 1980s in the US and Canada, respectively. More recently, Siddique et al.4 reported declines in pulmonary embolism mortality in the Medicare beneficiary population during 1984–1991. Given the changes in the US health care delivery system that have taken place since 1991, we investigated temporal mortality trends for pulmonary embolism mortality in the US for 1979–1996 to see if previously reported trends continued. This examination also allows for study of the continuance of various demographic contrasts reported by Lilienfeld et al.,2 i.e. the elevated risk of death for non-whites and for men.


    Methods
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
In the US, death certificates for all residents are coded, processed and tabulated by the National Center for Health Statistics of the Centers for Disease Control and Prevention (CDCP). These data are available through the CDCP Wonder System on the World Wide Web (http://wonder.cdc.gov/). These data were reviewed for deaths in which pulmonary embolism (ICD-9 rubric 415.1) was coded as the underlying cause. The annual age-adjusted rates by gender and race (‘white’, ‘black’ and ‘other’), using the 1970 US population as a standard, were obtained for each year of 1979–1996. The number of deaths that each age-adjusted rate was based upon was also recorded. For each race-gender combination, a linear regression equation was fitted with the year as an independent variable and the annual age-adjusted rate as the dependent one. The statistical significance of the regression coefficients (slopes) were then tested in the usual manner.

The annual age-specific mortality rates in the US by gender and race were then generated using the CDCP Wonder System for 1979 and 1996. The number of deaths that each age-specific rate was based upon and the corresponding population were also recorded. The percentage changes from 1979 to 1996 in the age-gender-specific rates among whites were then calculated. Standard z-tests were used to calculate the statistical significance of these percentages.


    Results
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
In 1996, 9027 deaths in the US were recorded with pulmonary embolism as the underlying cause. The age-adjusted pulmonary embolism death rates per 100 000 persons in the US in 1996 among white men, white women, black men, black women, other men, and other women are shown in Table 1Go. Black men experienced the highest mortality and other women, the lowest. Regardless of gender, blacks experienced the greatest mortality and other individuals the lowest mortality. In all three racial groups, men had greater mortality than women. The greatest contrast was seen among blacks, and the least, whites.


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Table 1 Annual age-adjusteda pulmonary embolism mortality per 100 000 persons, US 1996, by gender and race. Numbers in parentheses are the number of deaths
 
The annual age-adjusted pulmonary embolism death rates in the US for each of the six race-gender groups during 1979–1996 are shown in Figure 1Go. For all six race-gender groups, the general pattern of decline in mortality is seen. In general, within each race, male mortality is greater than female mortality in any given year, with the exception of 1986 and 1995 among other individuals. The gender mortality contrast present in 1979 among blacks is still present in 1996, though somewhat reduced in magnitude. For whites, the gender mortality contrast decreased gradually during the observation period. There is little gender mortality contrast among other individuals.



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Figure 1 Annual age-adjusted pulmonary embolism mortality in the US, by race and gender, 1979–1996

 
The parameters for the fitted linear regression model of pulmonary embolism mortality in the US during 1979–1996 are shown in Table 2Go. For all groups, the slope was negative and statistically significant at the 0.005 level. The greatest negative slope was for black men, and the least, other women. The greatest R2, the proportion of variance accounted for by the regression model, was observed for the model for white men, and the least, that for other women. Within each gender, blacks had the greatest decline and other individuals the least. Within each racial group, men had greater rates of decline than did women.


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Table 2 Parameters for the fitted linear regression modela of pulmonary embolism mortality in the US, 1979–1996, by gender and race
 
The changes in the annual age-specific pulmonary embolism mortality rates in the US between 1979 and 1996, by race and gender, are shown in Table 3Go. The decreases in the rates are substantial in all race-gender groups >=55 years. For whites and blacks, these decreases are uniformly statistically significant; they were not uniformly statistically significant for other men and women. With the exception of the 1–4 years old group, the 15–19 years old group and the 25–34 years old group, white men at all ages experienced declines in pulmonary embolism mortality. A similar comment applies to white women and black men; for both groups, there were significant declines among the elderly and middle-aged and non-significant increases among early adults.


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Table 3 Percentage change in annual age-specific pulmonary embolism mortality in the US between 1979 and 1996, by race and gender
 
The age-specific pulmonary death rates in the US during 1996 for white men, white women, black men, black women, other men, and other women are shown in Figure 2Go. Some patterns are evident in these data. First, with the exception of a slight decline in mortality during infancy, the rates increase throughout the life span. This increase is particularly notable in the second half of life. Only for other men in the oldest age group (85+ years) does the rate decline. Blacks have the highest death rate from pulmonary embolism at all ages. Other individuals experience the lowest pulmonary embolism mortality. White mortality is intermediate at each age. In general, male mortality is greater than female mortality at all ages, with the exception of black in early adulthood (female mortality exceeds male mortality).



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Figure 2 Age-specific pulmonary embolism mortality in the US, by race and gender, 1996

 

    Discussion
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
We found that pulmonary embolism mortality in the US during 1979–1996 declined among all age groups. The decline was continuous during the observation period. Decreases in death rates were concentrated in the elderly, though declines among the middle-aged were also observed in some race-gender combinations. The rates for blacks exceeded those for whites and white mortality exceeded that for other people. Men had greater mortality than women, particularly among blacks. Lastly, in 1996, age-specific pulmonary embolism mortality increased with ascending age for all six race-gender groups. The mortality patterns observed among the age-adjusted data apply to the age-specific data.

The first issue to be considered with regard to these data is their validity. There are little data on the reliability of death certificate statements of cause with regard to pulmonary embolism. This situation has remained unchanged for the past decade. Hence, it is difficult to know whether the mortality patterns observed reflect the occurrence of pulmonary embolism. Indeed, Proctor and Greenfield5 reported in 1997 that a considerable number of pulmonary embolism cases were not properly coded to the correct ICD-9 rubric (415.1). Whether this finding applied to mortality data was not reported. Previous reports of both Lilienfeld et al.2 and Soskolne et al.3 suggested that pulmonary embolism mortality in the US and in Canada from the early 1960s to the middle 1980s increased substantially. This result would be indicative of increased incidence of disease, improved recognition of disease, or both. More recent population-based incidence studies have suggested that the occurrence of the disease has declined.4,6

Population-based data on the incidence of pulmonary embolism in the US have been developed in relatively rural populations (Silverstein et al.6 for Olmsted County, Minnesota and Anderson et al.7 for Worchester, Massachusetts), in specific high-risk populations (Tuttle-Newhall et al.8 in North Carolina trauma patients), and among Medicare beneficiaries (Siddique et al.4,9). Silverstein et al.6 examined pulmonary embolism incidence trends in Olmsted County, Minnesota and found that they had declined between 1976 and 1990. Siddique et al.4,9 observed declines in mortality in the white Medicare population during 1984–1991, though not among blacks. The other population-based studies did not examine temporal trends in pulmonary embolism incidence. Cohen et al.10 relied upon autopsy data in the UK to conclude that the introduction of prophylactic measures and changes in hospital practice had reduced the prevalence of pulmonary embolism at autopsy in the UK between 1976 and 1990. Our observations of the changes in US pulmonary embolism mortality would be consistent with those of other investigators in the US and elsewhere.

The elevated death rate from pulmonary embolism among blacks was previously observed by Lilienfeld et al.2 This excess has been present in pulmonary embolism mortality in the US since the early 1960s. Kniffen et al.11 reported that among Medicare beneficiaries between 1986 and 1989, blacks were at elevated risk of the disease compared with whites. However, they did not examine any temporal data. Siddique et al.4,9 reported that between 1984 and 1991, white Medicare beneficiaries experienced a 15–16% decline in pulmonary embolism mortality. Black beneficiaries did not experience such a decline, in part as a result of decreased survival. These findings appear to be at odds with our own, in which blacks experienced the greatest rate of decline in pulmonary embolism mortality. We do not have an explanation for these differences except to note that Siddique et al. observed their population (a sample of the US elderly population) for a shorter time period. Population-based incidence studies in settings with black populations present might provide insight into the degree to which pulmonary embolism incidence and mortality is changing in the US black population compared with the white one. They would also facilitate our understanding of the lower risk of death experienced by other people. Piccioli et al.12 have noted that the clinical spectrum associated with pulmonary embolism in a registry setting is different from that based on randomized clinical trials. Population-based studies would compliment existing knowledge gained from randomized clinical trials and place these mortality patterns into perspective.

The decline in pulmonary embolism mortality among men was greater (as reflected by the slope in the regression model of the decline) than among women regardless of race. Other investigators (such as Kniffen et al.11 have observed that among Medicare beneficiaries, men experience pulmonary embolism at a greater rate than do women. Assuming no difference in survivorship, men would be expected to have greater mortality from the disease. The reason for men to experience a greater decline in mortality than women is not clear. Given that most of the decline occurred in the elderly, one might focus on differences between elderly men and women in the US during the past two decades. One difference is that elderly women have been increasingly using post-menopausal oestrogens. Although such preparations are thought to reduce the risk of myocardial infarction, it is not known if they have any impact on pulmonary embolism incidence or mortality. The Women's Health Initiative studies now in progress should clarify this issue. There may of course be other reasons for the decline to be greater for men than for women.

In summary, we observed a decline in pulmonary embolism mortality in the US population during 1979–1996. The decline was greatest among blacks, among men, and among the elderly. The reasons for this decline are not established. In 1996, blacks had an elevated risk of death from pulmonary embolism compared with whites or other individuals. Similarly, men had an elevated risk of mortality compared with women. These data suggest that there may have been favourable changes in the frequency of pulmonary embolism in the population. However, population-based incidence studies are needed to further our understanding of this common clinical condition.


    Notes
 
Bristol-Myers Squibb Corporation, PO Box 5400, HW 19-1.0b Princeton,NJ 08534-5400, USA. E-mail: David.Lilienfeld{at}bms.com


    References
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
1 Bell WR. Pulmonary embolism: progress and problems. Am J Med 1982;72:181–83.[ISI][Medline]

2 Lilienfeld DE, Chan E, Ehland J, Godbold JH, Landrigan PJ, Marsh G. Mortality from pulmonary embolism in the United States: 1962–1984. Chest 1990;98:1067–72.[Abstract]

3 Soskolne CL, Wong AW, Lilienfeld DE. Trends in pulmonary embolism death rates for Canada and the United States, 1962–87. Can Med Assoc J 1990;142:321–24.[Abstract]

4 Siddique RM, Siddique MI, Rimm AA. Trends in pulmonary embolism in the US elderly population: 1984 through 1991. Am J Public Health 1998;88:478–80.[Abstract]

5 Proctor MC, Greenfield LJ. Pulmonary embolism: diagnosis, incidence, and implications. Cardiovasc Surg 1997;5:77–81.[Medline]

6 Silverstein MD, Heit JA, Mohr DN, Petterson TM, O'Fallon WM, Melton LJ 3rd. Trends in the incidence of deep vein thrombosis and pulmonary embolism: 25-year population-based study. Arch Intern Med 1998;158:585–93.[Abstract/Free Full Text]

7 Anderson FA Jr, Wheeler HB, Goldberg RJ et al. A population-based perspective of the hospital incidence and case-fatality rates of deep vein thrombosis and pulmonary embolism. The Worcester DVT Study. Arch Intern Med 1991;151:933–38.[Abstract]

8 Tuttle-Newhall JE, Rutledge R, Hultman CS, Fakhry SM. Statewide, population-based, time-series analysis of the frequency and outcome of pulmonary embolus in 318 554 trauma patients. J Trauma 1997; 42:90–99.[ISI][Medline]

9 Siddique RM, Amini SB, Connors AF Jr, Rimm AA. Race and sex differences in long-term survival rates for elderly patients with pulmonary embolism. Am J Public Health 1998;88:1476–80.[Abstract]

10 Cohen AT, Edmondson RA, Phillips MJ, Ward VP, Kakkar VV. The changing pattern of venous thromboembolic disease. Haemostasis 1996;26:65–71.[ISI][Medline]

11 Kniffen WD Jr, Barron JA, Barrett J, Birkmeyer JD, Anderson FA Jr. The epidemiology of diagnosed pulmonary embolism and deep venous thrombosis in the elderly. Arch Intern Med 1994;154:861–66.[Abstract]

12 Piccioli A, Prandoni, Goldhaber GZ. Epidemiologic characteristics, management, and outcome of deep venous thrombosis in a tertiary-care hospital: the Brigham and Women's Hospital DVT registry. Am Heart J 1996;132:1010–14.[ISI][Medline]