An analysis of mortality follow-up through the National Death Index for a cohort of refinery and petrochemical workers

Along with our submission to the National Death Index (NDI) of a cohort of more than 23,000 petrochemical and refinery workers, we included 1,449 known U.S. deaths to determine the completeness of death ascertainment through the NDI. A number of factors that may affect follow-up were examined including sex, race, age and reporting area. Overall, NDI detected 97.1% of known deaths. Follow-up was slightly better for males (97.2%) than for females (92.0%) and was significantly better for whites (97.6%) than for nonwhites (92.0%). Analyses by reporting area showed very complete follow-up from all locations (93.4%-100%) except for the New York City area (71.4%). These findings indicate that NDI is an extremely useful source for vital status follow-up, though follow-up may be somewhat less complete for certain subgroups of an occupational study cohort.     

Utility of the National Death Index in ascertaining mortality in acquired immunodeficiency syndrome surveillance

To assess the utility of the National Death Index (NDI) in improving the ascertainment of deaths among people diagnosed with acquired immunodeficiency syndrome (AIDS), the authors determined the number and characteristics of additional deaths identified through NDI linkage not ascertained by using standard electronic linkage with Florida Vital Records and the Social Security Administration's Death Master File. Records of people diagnosed with acquired immunodeficiency syndrome between 1993 and 2007 in Florida were linked to the NDI. The demographic characteristics and reported human immunodeficiency virus (HIV) transmission modes of people whose deaths were identified by using the NDI were compared with those whose deaths were ascertained by standard linkage methods. Of the 15,094 submitted records, 719 had confirmed matches, comprising 2.1% of known deaths (n = 34,504) within the cohort. Hispanics, males, people 40 years of age or older, and injection drug users were overrepresented among deaths ascertained only by the NDI. In-state deaths comprised 59.0% of newly identified deaths, and human immunodeficiency virus was less likely to be a cause of death among newly identified compared with previously identified deaths. The newly identified deaths were not previously ascertained principally because of slight differences in personal identifying information and could have been identified through improved linkages with Florida Vital Records.     

Deafness and mortality: analyses of linked data from the National Health Interview Survey and National Death Index.

OBJECTIVE: To examine the association between age at onset of deafness and mortality. METHODS: The authors analyzed National Health Interview Survey data from 1990 and 1991--the years the Hearing Supplement was administered--linked with National Death Index data for 1990-1995. Adjusting for sociodemographic variables and health status, the authors compared the mortality of three groups of adults ages > or = 19 years: those with prelingual onset of deafness (< or = age 3 years), those with postlingual onset of deafness (> age 3 years), and a representative sample of the general population. RESULTS: Multivariate analyses adjusted for sociodemographics and stratified by age found that adults with postlingual onset of deafness were more likely to die in the given time frames than non-deaf adults. However, when analyses were also adjusted for health status, there was no difference between adults with postlingual onset of deafness and a control group of non-deaf adults. No differences in mortality were found between adults with prelingual onset of deafness and non-deaf adults. CONCLUSIONS: Adults with postlingual onset of deafness appear to have higher mortality than non-deaf adults, which may be attributable to their lower self-reported health status.     

Surveillance of mortality among atomic bomb survivors living in the United States using the National Death Index

BACKGROUND: The National Death Index is a useful source to establish the death of an individual and to determine the cause of death. We identified deaths in atomic bomb survivors in the United States who were lost to follow-up through the National Death Index, and examined the completeness of mortality ascertainment in atomic bomb survivors in the US through the National Death Index. METHODS: Since 1977, biennial medical examinations of atomic bomb survivors in the US have been conducted. The 1,073 atomic bomb survivors in the US included 764 individuals who had medical examinations at least once in sixteen years from 1977 through 1993 and 309 individuals who reported atomic bomb survivorship to medical examination project themselves. Of the 1,073 survivors living in the US, 471 people who participated in the ninth health examinations of atomic bomb survivors living in the US in 1993 were removed, and two people among the remaining 602 individuals had no information about their birth dates and Social Security numbers. An investigation of those deceased between 1979 and 1993 was conducted among 600 of the atomic bomb survivors in the US. Death certificates for atomic bomb survivors in the US were requested from the National Death Index. A comparison was made between the information on the death certificates acquired through the National Death Index and the data ascertained from the medical examination project conducted from 1979 through 1993. RESULTS: Forty-nine death certificates were obtained using the National Death Index. By sex, the dominant cause of death in females was malignant neoplasm, accounting for 53%. In males, it was circulatory disease, accounting for 37%. The National Death Index and the medical examination project determined that 57 deaths had occurred between 1979 and 1993. The sensitivity and specificity of the National Death Index is 86% and 97% respectively. CONCLUSION: It is suggested that the National Death Index is useful to follow up mortality among atomic bomb survivors in the US.     

Mortality ascertainment of participants in the National Wilms Tumor Study using the National Death Index: comparison of active and passive follow-up results

Long term studies of childhood cancer survivors are hampered by difficulties in tracking young adult participants. After performing a National Death Index (NDI) search we sought to identify which factors best predicted a match among known decedents from the National Wilms Tumor Study (NWTS) and to determine if record linkage could substitute for missing follow-up in a cohort of NWTS survivors. To our knowledge, this is the first study to compare passive mortality follow-up using the NDI to active follow-up of a childhood and young adult population. Records for 984 known decedents and 3,406 subjects whose January 1, 2002 vital status was unknown were sent to the NDI in June 2003. In April 2005 NWTS follow-up records were used to reassess January 1, 2002 vital status. Matches were established for 709 of 789 known decedents (sensitivity 89.9%) with a date of death between 1979 and 2001, the calendar period covered by the NDI at the time of the search. No matches were identified among 1,052 subjects known to be alive in 2002 (specificity 100%). Factors associated with decreased sensitivity were an unknown social security number (sensitivity 87.8%), Hispanic ethnicity (76.4%) and foreign birth (56.5%). For 2,351 subjects with 2002 vital status unknown who had 13,166 pre 2002 person-years of missing observation, only 18 deaths were ascertained by the NDI whereas 79.3 were expected based on NWTS mortality data. Mortality analyses based strictly on NDI search results and those based on NWTS follow-up augmented with NDI search results yielded inflated estimates of the 15 year survival rate when compared with estimates based on NWTS active follow-up. Match rates were comparable to those observed in adult populations. Since the same selection factors were likely associated with NDI failure to match and NWTS loss to follow-up, use of the NDI to fill in missing follow-up data appears unwarranted.     

Comparison of National Death Index and World Wide Web death searches

The authors used the National Death Index and a World Wide Web Internet site that searches the Social Security Administration master files of deaths to determine the mortality status of 1,000 US subjects from the College Alumni Health Study. Subjects were classified as definitely dead, possibly dead, or presumed alive. Of 246 definite deaths pinpointed by the National Death Index, the World Wide Web identified 94.7% of them. Of 438 men presumed alive according to the National Death Index, the World Wide Web identified 97.5% of them. However, the World Wide Web was not useful for identifying deaths of women. This study demonstrated that the World Wide Web may provide an alternative, inexpensive method of determining the mortality status of subjects in relatively small epidemiologic studies.     

The Australian National Death Index: an assessment of accuracy

OBJECTIVE: The Australian National Death Index (NDI) provides a comprehensive and accessible source of mortality information for epidemiological research. Use of the index requires a probabilistic matching process that inevitably results in some inaccuracy. In this paper, accuracy is assessed. METHODS: Results of a matching process against the NDI performed by the Australian Institute of Health and Welfare in Canberra were compared with information provided by the Medical Device Outcomes study cohort and their families (n = 2,990). Indices of accuracy for the NDI were calculated. RESULTS: For this particular study, the NDI has sensitivity 88.8% (84.9-92.8) and specificity 98.2% (97.4-98.7). CONCLUSIONS AND IMPLICATIONS: The relatively low sensitivity is of some concern to those using the NDI for health outcomes research. The importance of such a national database is evident; however, to improve accuracy the introduction of a national unique patient identifier is necessary.     

Ascertainment of vital status through the National Death Index and the Social Security Administration

Ascertainment of the vital status of individuals is of central importance to epidemiologic studies which monitor mortality as an end point. Utilizing identifying information collected in 1973-1974, the Hypertension Detection and Follow-up Program, a prospective, multicenter study, followed 25,362 individuals to determine eight-year mortality. In the most recent follow-up, there were 617 individuals whose vital status was not known. Available identifying information on these and on all 1,322 participants known to have died in 1979-1981 was submitted to the National Death Index (NDI) for possible confirmation of vital status. A subset of individuals who had Social Security numbers (490 lost to follow-up and 1,154 known deaths) was also submitted to the Social Security Administration (SSA). The NDI correctly identified 87.0% of the known deaths. Of the 1,154 known deaths (those with known Social Security numbers) submitted to both agencies, the NDI identified 93.1% and the SSA 83.6%. Significant variations by race and sex were noted in the identification rates, in part because of Social Security number discrepancies. False matches through the NDI matching process occurred for 10.4% of the known deaths. In the more restrictive SSA search, only 0.5% false matches resulted. For those lost to follow-up, vital status was ascertained in 57.1%. This paper describes the relative efficacy and attributes of the use of these systems to ascertain vital status.     

Health status before and mortality after hip fracture.

A cohort study was done to determine the direct impact of hip fracture on mortality in older people. Survival was compared between 211 hip fracture patients from a defined area and 201 non-hip fracture control subjects randomly selected from the same area. The mortality rate 1 year after hip fracture was 21.7%; 1-year mortality in the comparison group was 4.7%. The crude hazard ratio for hip fracture and mortality was 4.0 (95% confidence interval [CI] = 2.2, 7.4); adjusting for multiple health-related variables reduced it to 3.3 (95% CI = 1.7, 6.5). This finding suggests that the observed excess mortality after hip fracture is not explained by poor prefracture health status.     

Suicide mortality of Eastern European regions before and after the Communist period

The aim of this study was to investigate the spatial distribution of Eastern European suicide mortality both before and at the end of the Communist period, as well as the changes that occurred during this period. Regional data on suicide mortality were collected from Czarist "European Russia" in 1910 and from the corresponding area in 1989. The distribution of suicide mortality was mapped at both points in time. Regional continuity over time was further studied with the help of geographical units specially constructed for this purpose. In 1910, suicide mortality was found to be high in the northern Baltic provinces, in the urban parts of north and central Russia, the more urbanized parts of northern and western Poland, in east Ukraine, and in the northern Caucasus, while suicide rates were generally low in south Russia, Dagestan, and in southern Poland. In 1989, suicide mortality was highest in the Urals, the east Russian "ethnic" areas, and in southeast Russia. The rates were low in Poland, Moldavia, and in most of the northern Caucasus. The across-time analysis using specially constructed comparison units showed that the spatial distributions of suicide mortality in 1910 and 1989 were not correlated with each other. Additional analyses pointed to a short-term consistency of regional patterns both in the 1900s-1920s and the 1980s-1990s. The lack of regional continuity in suicide mortality in the area may imply an absence of strong and continuous regional cultures, or a strong influence of other factors, such as societal modernization, on suicide mortality. Suicide as an act changed its social nature during the Communist period, becoming more normal, and more equally distributed among social classes and geographical locations.     

Quality deficits in the Spanish National Death Index: lessons learned from studying the mortality of two cohorts of people admitted to drug abuse treatment

Objective

The use of the Spanish National Death Index (S-NDI) is increasing as it is free and easily accessible. Prompted by unexpected findings when linking two cohorts of patients with the S-NDI, this study was performed to evaluate the quality of mortality data from this source.

Methods

Individual records of two cohorts of persons admitted to drug abuse treatment in Barcelona (n = 19,974) and Madrid (n = 17,557) were linked with the S-NDI and then with the National Statistics Institute (NSI) to assign vital status. The sensitivity and specificity of the S-NDI in relation to the NSI and estimates of mortality with both systems were obtained. Underestimation of mortality by the S-NDI for the same period in the whole of Spain was also calculated.

Results

For Madrid, from 1997-2008, independent searches in the S-NDI underestimated mortality by 18.9% compared with the NSI. A subsequent individualized search limited to deaths detected by the NSI but not by the S-NDI reduced underestimation to 13.9%. For Barcelona, underestimation with a combined search (independent plus limited) was 3.3%. From 2001-2002, underestimation with combined searches reached 32.3% in Madrid and 7.3% in Barcelona. Underestimation was also seen in the general Spanish population (1.8% in 1997-2008 and 9.3% in 2001-2002). From 1997-2008, the specificity of independent searches in the S-NDI was 100%, but its sensitivity in Madrid was only 81%.

Conclusions

The quality of the S-NDI is good enough for many uses in the health sector, but this index underestimates mortality with substantial spatiotemporal variations. The quality of the S-NDI could be increased by improving its search algorithms, enabling on-line tabulations of the main results, and introducing quality controls and routine evaluations.     

A comparison of the National Death Index and Social Security Administration databases to ascertain vital status

We compared vital status follow-up by the National Death Index and the Social Security Administration for a cohort of breast cancer patients. Only the National Death Index allowed follow-up for subjects with an unknown Social Security number. All of the deaths identified by the Social Security Administration were reported by the National Death Index. No subject reported to be alive by the Social Security Administration matched a National Death Index record. Subjects with inaccurate identifying information were more effectively followed up by the National Death Index. The National Death Index more accurately reported dates of death.     

Arthritis and mortality in the epidemiological follow-up to the National Health and Nutrition Examination Survey I.

Subsets were analyzed of respondents from the Epidemiological Follow-up to the National Health and Nutrition Examination Survey I (NHANES I) who (1) answered a general arthritis question reflecting whether a doctor told the respondent that she or he had arthritis, (2) answered seven pain, swelling, and stiffness questions, and (3) had radiographs of knees and hips assessed for osteoarthritis at the time of the initial survey during the early 1970s. Data for the follow-up were collected between 1982 and 1984 and included 1,491 fatalities in the largest subsample analyzed here. The dependent variable was months of survival after the initial interview. No distinction was drawn between rheumatoid arthritis versus osteoarthritis. The NHANES I contained only limited information on rheumatoid arthritis versus osteoarthritis. Additional covariates included age, age squared, education, race, marital status, diastolic blood pressure, and body mass. After adjusting for age, no statistically significant associations emerged between answers to the general arthritis questions or any of the seven pain questions on the one hand, and mortality on the other. Similar statistically insignificant results were found when the association between radiographic diagnoses of osteoarthritis in the hips and months of survival was considered after adjusting for age. These statistically insignificant results persisted in repeated testing, which alternately included and excluded a number of covariates, and in separate subsamples of women, men, and persons older and younger than age 50. Some evidence was found, however, for a negative, statistically significant association between radiographic knee diagnoses of osteoarthritis and survival, especially among women, even after adjusting for covariates. These mixed results (1) do not discredit findings elsewhere suggesting that rheumatoid arthritis is associated with early death, since it is likely that the great majority of respondents answering in the affirmative to the general arthritis or seven pain questions in the NHANES I had osteoarthritis, and (2) suggest that future surveys should make greater attempts to distinguish between rheumatoid arthritis and osteoarthritis.     

Infectious diseases before and after German unification: trends in mortality and morbidity

After the fall of the Berlin Wall in 1989 the former communist countries of central and eastern Europe underwent substantial social and economic changes that had a major impact on health. The situation of the former German Democratic Republic was unique in that its existing institutions were replaced rapidly and it was quickly integrated economically with the West. This study describes recent trends in morbidity and mortality from infectious diseases in East and West Germany before and after unification using routine data from 1980 onwards. Substantial differences in morbidity and mortality resulting from infectious diseases were observed between East and West Germany. These seem to be the complex result of societal and health system differences in both parts of Germany before unification, differing population dynamics and health behaviours, and an increasing westernisation in the eastern part of Germany during recent years.