We read with interest the recent article by Cassell and Clapperton describing the decreasing trend in fall-related hip fracture rates among people aged 65 and older in Victoria, Australia from 1998/99 to 2008/09 [1].Over this time period, hip fracture rates decreased by 25 % among men and 23 % among women.Similar trends have been seen in other countries.We previously reported trends in hip fracture hospitalization rates among people aged 65 and older in the USA from 1990 to 2010 [2,3].Looking at the time period from 1998 to 2008, US rates declined by 22 % for men and 28 % for women-very similar to Cassell and Clapperton's results.Although the overall findings of this Australian study and our US studies are comparable, there are also some important differences.Cassell and Clapperton examined trends in hip fracture rates for men and women aged 65 and older separately and for both sexes combined by 5-year age groups, while we looked at trends in rates by 10-year age groups for men and women aged 65 and older separately.We found that most rates for men and women decreased significantly from 1996 to 2010, with the sharpest decline occurring among women aged 85 and older (annual percent change=-3.3;95 % confidence interval=-4.2 to -2.3).However, rates did not decrease significantly among men aged 65 to 74.Over the next two to three decades, these trends are likely to result in fewer hip fractures than Cassell and Clapperton's study might suggest.Underlying causes for these trends are unclear, but it does not appear to be a result of osteoporosis treatment with bisphosphonates, which is not widely used and often discontinued due to unpleasant side effects [4,5].Other

We examined age- and sex-specific hip fracture hospitalization rates among people aged 65 and older using 1990–2010 National Hospital Discharge Survey data. Trends calculated using Joinpoint regression analysis suggest that future increases in hip fractures due to the aging population will be largely offset by decreasing hip fracture rates among women. However, this trend will be counterbalanced by rising numbers of hip fractures among men.

Objective. To obtain historical estimates of US asthma incidence from 17 years of health survey data. Methods. The 1980 through 1996 National Health Interview Survey contained a question asking about the time of asthma onset in persons with asthma. Annual past year incidence estimates were calculated from self-reports of asthma status. Results. Incidence increased from 2.5 per 1,000 (SE 0.37) in 1980 to 6.0 per 1,000 (SE 0.75) in 1996. Incidence increased faster in children than in adults and increased in females but not in males during this time. Conclusion. These findings suggest that increasing asthma incidence contributed to the increasing prevalence during this time.

PROBLEM/CONDITION:Asthma, a chronic respiratory disease with episodic symptoms, increased in prevalence during 1980-1996 in the United States. Asthma has been the focus of numerous provider interventions (e.g., improving adherence to asthma guidelines) and public health interventions during recent years. Although the etiology of asthma is unknown, adherence to medical treatment regimen and environmental management should reduce the occurrence of exacerbations and lessen the hardship of this disease. CDC has outlined a public health approach to asthma that includes comprehensive analyses of national surveillance data on prevalence, health-care use and mortality, and a strategy to improve the timeliness and geographic specificity of asthma surveillance data.REPORTING PERIOD COVERED:This report presents national data on asthma for self-reported prevalence (1980-1996 and 2001-2004); self-reported attacks (1997-2004); visits to physicians' offices (1980-2004), hospital outpatient departments (1992-2004), and emergency departments (1992-2004); hospitalizations (1980-2004); and deaths (1980-2004).DESCRIPTION OF SYSTEMS:The National Health Interview Survey includes questions about asthma prevalence and asthma attacks. Physicians' office visit data are collected in the National Ambulatory Medical Care Survey, emergency department and hospital outpatient data in the National Hospital Ambulatory Medical Care Survey, hospitalization data in the National Hospital Discharge Survey, and death data in the Mortality component of the National Vital Statistics System.RESULTS:From 1980 to 1996, 12-month asthma prevalence increased both in counts and rates, but no discernable change was identified in asthma attack estimates since 1997 or in current asthma prevalence from 2001 to 2004. During the period of increasing prevalence, patient encounters (office visits, emergency department visits, outpatient visits, and hospitalizations) for asthma increased. However, rates for these encounters, when based on the population with asthma, did not increase. Although the rate of asthma deaths increased during 1980-1995, the rate of deaths has decreased each year since 2000. During 2001-2003, current asthma prevalence was higher in children (8.5%) compared with adults (6.7%), females (8.1%) compared with males (6.2%), blacks (9.2%) compared with whites (6.9%), those of Puerto Rican descent (14.5%) compared with those of Mexican descent (3.9%), those below the federal poverty level (10.3%) compared with those at or above the federal poverty level (6.4% to 7.9%), and those residing in the Northeast (8.1%) compared with those residing in other regions (6.7% to 7.5%). Among persons with current asthma, whites and blacks were equally likely to report an attack during the preceding 12 months. Women with current asthma were more likely to report asthma attacks than men, and children were more likely than adults. The rate for asthma health-care encounters, regardless of place (physician office, emergency department, outpatient department, or hospital), when based on the population with asthma, did not differ by race. However, whites with current asthma had higher rates for physician offices, and blacks had higher rates for hospital-based sites (e.g., outpatient clinics and emergency departments).INTERPRETATION:The findings in this report suggest that from 1980 through the mid-1990s, increases in asthma prevalence played a substantial role in the increases in patient encounter measures used in asthma surveillance. Because no primary strategies for preventing asthma have been identified, efforts to control asthma exacerbations through interventions that promote adhering to proper medical regimens and reducing exposures to causes of asthma exacerbations should continue to be pursued.

Heterogeneous population densities complicate comparisons of statistical power between hypothesis tests evaluating spatial clusters or clustering of disease. Specifically, the location of a cluster within a heterogeneously distributed population at risk impacts power properties, complicating comparisons of tests, and allowing one to map spatial variations in statistical power for different tests. Such maps provide insight into the overall power of a particular test, and also indicate areas within the study area where tests are more or less likely to detect the same local increase in relative risk. While such maps are largely driven by local sample size, we also find differences due to features of the statistics themselves. We illustrate these concepts using two tests: Tango's index of clustering and the spatial scan statistic. Furthermore, assessments of the accuracy of the ‘most likely cluster’ involve not only statistical power, but also spatial accuracy in identifying the location of a true underlying cluster. We illustrate these concepts via induction of artificial clusters within the observed incidence of severe cardiac birth defects in Santa Clara County, CA in 1981. Copyright © 2006 John Wiley & Sons, Ltd.