Underestimation Of Incidence Rates Research Articles

The epidemiology of fractures in Denmark in 2011.

SummaryIn the present study, we used national health care databases to estimate fracture incidence rates (IRs) and compared these IRs based on imputed data. We showed that imputation could lead to both over- and underestimation of IRs, and future research should therefore focus on how to improve those imputations.IntroductionOsteoporosis is a major public health burden through associated (osteoporotic) fractures. In Denmark, the incidence rates (IRs) of hip fracture are widely available. However, there is limited data about other fracture sites. A recent report could only provide imputed IRs, although nationwide data is readily available in electronic healthcare databases. Therefore, our aim was to estimate fracture site-specific IRs for Denmark in 2011 and to compare those to the previously reported imputed data.MethodsData from the Danish National Hospital Discharge Register was used to estimate age- and gender-specific IRs for any fracture as well as for different fracture sites in the Danish population aged 20 years and older in 2011. Hip fracture IRs were stratified to sub-sites, and IRs were determined for all hip fractures which were confirmed by surgery.ResultsThe total number of incident fractures in 2011 was 80,760 (IR 191, 95 % confidence interval (CI) 190–192 (per 10,000 person-years)), of which 35,398 (43.8 %, IR 171, 95 % CI 169–173) occurred in men and 45,362 (56.2 %, IR 211, 95 % CI 209–213) in women. The majority of the fractures occurred in the population aged 50 years and older (n = 50,470, IR 249, 95 % CI 247–251). The numbers of any hip fracture were lower than the previously imputed estimates, whereas the number of forearm fractures was higher.ConclusionWe showed age- and gender-specific fracture rates for any fracture as well as for different fracture sites. The IRs of most fracture sites increased with age. Estimating the number of fractures for Denmark based on imputation of data from other countries led to both over- and underestimation. Future research should therefore focus on how to improve those imputations as not all countries have nationwide registry data.

Diabetes as a Tracer Condition in International Benchmarking of Health Systems

OBJECTIVE—To assess the performance of health systems using diabetes as a tracer condition. RESEARCH DESIGN AND METHODS—We generated a measure of “case-fatality” among young people with diabetes using the mortality-to-incidence ratio (M/I ratio) for 29 industrialized countries using published data on diabetes incidence and mortality. Standardized incidence rates for ages 0–14 years were extracted from the World Health Organization DiaMond study for the period 1990–1994; data on death from diabetes for ages 0–39 years were obtained from the World Health Organization mortality database and converted into age-standardized death rates for the period 1994–1998, using the European standard population. RESULTS—The M/I ratio varied >10-fold. These relative differences appear similar to those observed in cohort studies of mortality among young people with type 1 diabetes in five countries. A sensitivity analysis showed that using plausible assumptions about potential overestimation of diabetes as a cause of death and underestimation of incidence rates in the U.S. yields an M/I ratio that would still be twice as high as in the U.K. or Canada. CONCLUSIONS—The M/I ratio for diabetes provides a means of differentiating countries on quality of care for people with diabetes. It is solely an indicator of potential problems, a basis for stimulating more detailed assessments of whether such problems exist, and what can be done to address them.

Diabetes as a Tracer Condition in International Benchmarking of Health Systems

To assess the performance of health systems using diabetes as a tracer condition. We generated a measure of "case-fatality" among young people with diabetes using the mortality-to-incidence ratio (M/I ratio) for 29 industrialized countries using published data on diabetes incidence and mortality. Standardized incidence rates for ages 0-14 years were extracted from the World Health Organization DiaMond study for the period 1990-1994; data on death from diabetes for ages 0-39 years were obtained from the World Health Organization mortality database and converted into age-standardized death rates for the period 1994-1998, using the European standard population. The M/I ratio varied >10-fold. These relative differences appear similar to those observed in cohort studies of mortality among young people with type 1 diabetes in five countries. A sensitivity analysis showed that using plausible assumptions about potential overestimation of diabetes as a cause of death and underestimation of incidence rates in the U.S. yields an M/I ratio that would still be twice as high as in the U.K. or Canada. The M/I ratio for diabetes provides a means of differentiating countries on quality of care for people with diabetes. It is solely an indicator of potential problems, a basis for stimulating more detailed assessments of whether such problems exist, and what can be done to address them.

Incidence of Dementia in a Rural Community in Spain: The Girona Cohort Study

Background: Information on dementia incidence in Spanish populations is still scarce, and there is a dearth of prospective studies. Objective: To estimate the incidence rates of dementia, Alzheimer’s disease (AD) and vascular dementia (VaD) in a population cohort aged 75 and over in a rural area in Spain. Methods: A prospective population cohort study over a 5-year period in 8 rural villages in the province of Girona. The baseline study in 1990 identified 200 prevalent cases of dementia. The dementia-free cohort included 1,260 persons aged 75 and over. This was the sample used for the incidence study. We rescreened and selectively reexamined this group in 1995 using a two-phase procedure consisting of a screening interview at home using the MMSE. Diagnoses of dementia, AD and VaD were established using the Cambridge Examination for Mental Disorders of the Elderly for surviving participants. For deceased participants, we used the Retrospective Collateral Dementia Interview to establish a diagnosis of dementia and AD according to DSM-III-R diagnostic criteria. Results: Information was obtained for 91% of the subjects at risk; 122 incident cases of dementia were identified. Incidence rates per 1,000 person-years at risk were 23.2 (95% CI = 19.1–27.3) for dementia, 10.8 (95% CI = 7.8–13.7) for AD and 9.5 (95% CI = 6.7–12.1) for VaD. All dementia subtypes showed an age-dependent pattern. Females had a relative risk of 1.8 (95% CI = 1.0–3.4) to develop AD. The inclusion of deceased cases with manifestations of dementia increased the rate of dementia incidence in 7.1 cases/1,000 person-years at risk. Conclusion: Incidence rates were similar to those reported by other cohort studies. All dementia subtypes increased with age, but incidence rates did not increase exponentially in the oldest old. Females were at increased risk for AD. The inclusion of information about dementia symptoms from relatives of deceased participants was useful in order to avoid underestimation of the dementia incidence rates. Underestimation of the incidence rates was more important in those aged 75–84 years.