Variation In Incidence Of Disease Research Articles

Variations in 'avoidable' mortality: a reflection of variations in incidence?

Variations in 'avoidable' mortality may reflect variations in the quality of care, but they may also be due to variations in incidence or severity of diseases. We studied the association between regional variations in 'avoidable' mortality and variations in disease incidence. For a selection of conditions we also analysed whether the proportion of in-hospital deaths can explain the regional variations in incidence-adjusted mortality. Relative risks for mortality, incidence, incidence-adjusted mortality and in-hospital mortality (1984-1994) were calculated by log-linear regression. Linear regression was used to examine the relationship between mortality and incidence on the one hand, and between incidence-adjusted mortality and in-hospital mortality on the other. Significant regional mortality variations were found for cervical cancer, cancer of the testis, hypertensive and cerebrovascular disease, influenza/pneumonia, cholecystitis/lithiasis, perinatal causes and congenital cardiovascular anomalies. Regional mortality differences in general were only partly accounted for by incidence variations. The only exception was cervical cancer, which no longer showed significant variations after adjustment for incidence. The contribution of inhospital mortality variations to total cause-specific mortality variations varied between conditions: the highest percentage of explained variance was found for mortality from CVA (60.1%) and appendicitis (29.2%). Incidence data are a worthy addition to studies on 'avoidable' mortality. It is to be expected that the incidence-adjusted mortality rates are more sensitive for quality-of-care variations than the 'crude' mortality variations. Nevertheless, further research at the individual level is needed to identify possible deficiencies in health care delivery.

Association of a Phloem-Limited Bacterium with Yellow Vine Disease in Cucurbits

Since 1991, a new disease of cucurbits in central Texas and Oklahoma, designated yellow vine, has resulted in the decline and plant death of watermelon, cantaloupe, squash, and pumpkin. Affected plants are characterized by leaf yellowing, phloem discoloration, and plant collapse. Year-to-year variation in disease incidence has ranged from spotty outbreaks to complete crop loss in early-planted watermelon fields. A systematic investigation to determine the causal agent of the disease included pathogen isolation attempts, transmission tests, serological assays with various antisera (enzyme-linked immunosorbent assay and Western blotting), and DNA hybridizations with selected probes (dot and Southern blots). None of these tests revealed a consistent relationship between the expression of yellow vine symptoms and the presence of a particular microorganism or virus in the plant. However, transmission electron microscopic examination showed the consistent presence of a bacterium in the phloem sieve elements of symptomatic plants. The rod-shaped bacteria, observed only in symptomatic cucurbits, measured 0.25 to 0.5 μm in width and 1.0 to 3.0 μm in length and were surrounded by a triple-layered cell envelope.

Increasing incidence of myelodysplastic syndromes: real or fictitious?

Over the past 10-20 years, there has been a growing interest in the myelodysplastic syndromes (MDS). Due to difficulties of diagnosis, classification and case recording, the epidemiological features of MDS are still poorly defined. Recently, a number of cancer registries have published data on the regional occurrence of MDS, suggesting that MDS are much more common than previously thought. The crude incidence of MDS in these studies was 3.5-12.6 per 100,000 population per year. In people over the age of 70 years, incidence rates varied between 15 and 50 per 100,000 per year. Contrary to the assumption of most hematologists, cancer surveys usually failed to demonstrate a rising incidence of MDS. In those studies showing a significant increase in MDS, the rising number of cases was probably due to increased physician awareness and extended use of invasive diagnostic procedures in elderly people. Differences in incidence figures between regional studies may be attributed to several causes, including regional variations in disease incidence, small and ill-defined reference populations, bias due to patient referral patterns, varying intensity of diagnostic procedures and different observation periods. Because of the paucity of clinical symptoms and insignificance of morphological bone marrow changes particularly in early stage MDS, the currently available incidence figures are likely to underestimate the true incidence of MDS. Large-scale epidemiological studies are required for obtaining truly representative statistics on the incidence and prevalence of the MDS. In industrialized countries, a dramatic increase in these disorders can be expected over the next few decades due to the 'greying' of the population.

Variation in the resistance of Vicia faba to Ascochyta fabae in relation to disease development in field trials

The epidemic development of Ascochyta fabae in artificially infected field trials was studied in order to define resistance criteria and assess the variation in resistance of infected lines of faba bean. Large differences were demonstrated among French winter lines during the 1985/86 and 1986/87 growing seasons. All the scoring systems allowed the differentiation of very susceptible and resistant material, but disease indices, which account for the number and intensity of lesions, were more precise. The different phases of the epidemic are described on the basis of the variation in disease incidence on foliage and on pods during the 1986/87 cropping season in Brittany. There were three phases in disease development: initiation, spread throughout foliage, and pod infection, and these were all influenced by host resistance. On a very susceptible line, the disease spread was seen as an increase in the number and size of lesions and rapidly developed up the plant. Low disease indices observed on the resistant line 29 H were due to the small size and low frequency of lesions, resulting in a reduced area of foliage affected.

Methods of Mapping and Identifying Small Clusters of Rare Diseases with Applications to Geographical Epidemiology

Geographical variation operates at a variety of scales. Methods of mapping variation in disease incidence between different countries or even counties are relatively well developed. When, however, the question relates to much smaller aggregations (that is, “clustering”), attention has mainly been restricted to areas near putative point hazards; the majority of cases are excluded from such an investigation. In this study we show how clustering may be investigated and displayed in such a way that it becomes a powerful tool in epidemiological research. As examples we use incidence data from the Yorkshire health region for selected childhood cancers and adult haematopoietic malignancies. The methods would readily extend to any small clusters of rare events.

Myelin proteolipid protein-induced experimental allergic encephalomyelitis. Variations of disease expression in different strains of mice.

Strains of mice with diverse genetic backgrounds were tested for susceptibility to experimental allergic encephalomyelitis (EAE) induced by myelin proteolipid protein. EAE was elicited in all strains of mice tested, but the clinical and histologic features varied. SJL (H-2s) mice had a high incidence of both clinical and histologic disease characterized by early onset of clinical signs. Inguinal lymph node T cells from diseased animals responded specifically [( 3H]thymidine incorporation) to proteolipid protein and not to myelin basic protein. In contrast, BALB/c (H-2d), DBA/1 (H-2q), C57BL/6 (H-2b), AKR (H-2k), CBA (H-2k), C3H (H-2k), B10.BR (H-2k), and C57BR (H-2k) mice showed a later onset of clinical signs and typically a lower disease incidence. However, the most marked variations in disease incidence occurred among BALB/c (H-2d) substrains in which the incidence of EAE ranged from eight of nine (BALB/cPt) to complete resistance (BALB/cWt and BALB/cORNL). Because these BALB/c substrains were initially derived from the same inbred genetic source and are serologically identical at H-2, these results suggest that expression of proteolipid protein-induced EAE in the mouse involves additional loci outside the MHC.

Use of a food animal health resource management system for dairy herds

The objectives of this paper are to describe a farm record system used on a sample of Michigan dairy farms and to report on the incentive mechanism used to maintain the farmer’s interest in data collection from 1981-1985 while the program was developed. Associated with the above objectives, an animal health management system (FAHRMX) was developed to collect and utilize data on production, animal management, health, and economics. The system was designed to serve multi-veterinarian practices and their clients, and also for other agri-business support systems. Dairymen provided events data on a daily basis and veterinarians provided data on services to their clients as it occurred. DHIA production data were added at monthly intervals and epidemiologic data were added annually to the data base. A computer system was developed which represented a hierarchical-distributive network which placed processing capabilities, data storage, and retrieval functions at the appropriate level such that it supplied decision makers information on a cost-effective manner. Management aids and reports were generated for use by the veterinarian and dairyman upon demand, but were most often requested weekly. Herd health reports were generated monthly and contained management, health, and reproductive indicies. The evaluation of 2847 lactations and 21 herds revealed an average occurrence of 1.8 services per conception, 117 days open and a lactational disease incidence rate of 17.5% for reproductive tract infections, 15.1% for clinical mastitis, 12.5% for cystic ovaries, and 7.5% for retained placenta. Most striking was herd-to-herd variation in disease incidence. The value of the information to the user contributed to the quality of data input and was a motivation to the participants to maintain the program during its development.

The use of cultivar trials records in assessing the incidence of cereal disease in England and Wales. I. Septoria nodorum in wheat and Rhynchosporium secalis in barley

SUMMARYThe incidence of Septoria nodorum and Rhynchosporium secalis in N.I.A.B. cultivar trials of wheat and barley respectively showed marked regional and seasonal variation. Peak annual incidence of the two diseases often coincided. Levels of S. nodorum infection in winter wheat generally exceeded those in spring wheat, while levels of R. secalis in winter and spring barley were usually similar. Annual peaks in mean disease levels were associated with above average rainfall and raindays and below average temperatures, especially during the period of epidemic development. Regional variation in disease incidence reflected the association with high rainfall. S. nodorum infection in wheat was more widespread, and incidence of leaf infection was higher, than R. secalis in barley. Annual and regional incidence of S. nodorum and R. secalis in trials was similar to that recorded in the Plant Pathology Laboratory surveys of commercial crops. Disease records from cultivar trials can provide useful additional information on the behaviour of S. nodorum and R. secalis nationally.

The use of a Kolmogorov--Smirnov type statistic in testing hypotheses about seasonal variation.

This paper presents a non-parametric method for testing departures from a uniform seasonal variation in incidence of disease. The method may be used either with exact dates of incidence when they are available or with monthly totals. It is equally valid for sinusoidal and non-sinusoidal departures from uniformity. A simulation study shows it to be much more powerful than other non-parametric alternatives and nearly as powerful as Edwards's test in detecting sinusoidal departures.