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PubMed2007

Using hierarchical models to attribute sources of variation in consumer assessments of health care.

The Consumer Assessments of Healthcare Providers and Systems (CAHPS) Medicare Advantage (MA-CAHPS) survey has provided extensive and uniform data for 8 years on the quality of Medicare health plans in the United States. The complex structure of the data makes hierarchical modelling an appropriate analytic tool. After describing the CAHPS survey and the analytic methods used in standard reports, we review research using two multilevel modelling strategies, each addressing a different aspect of the structure of the CAHPS data. The first fits a 2-level Fay-Herriott-type model to data aggregated by plan to estimate plan-level correlations among summary scores on different items. By forming separate measures for healthier and sicker members of each plan, we were able to determine which items measured distinct dimensions of quality depending on health status. The second analysis evaluated the relative contributions of geography and organizational units to the various quality measures, and the amount of variation over time in each. Geographical variation predominated for aspects of member experiences that are not typically under the direct control of plans, and the geographical effects were very stable over time. Each of the two analyses can be regarded as a simplification for particular objectives of a larger underlying model. Further methodological development is needed to better characterize variation in quality.

Data Interpretation, Statistical↗

PubMed2005

A meta-analysis of perioperative beta blockade: what is the actual risk reduction?

BACKGROUND: The use of beta blockers in surgical patients has been suggested to decrease perioperative cardiac events. However, the overall risk reduction, on the basis of solely aggregate data from randomized studies, is unknown. The objective is to evaluate the effect of perioperative beta blockade in noncardiac surgery for protection against mortality or cardiac events. METHODS: We performed a formal meta-analysis. The Medline database was searched for articles published from 1966-2004 by using the terms perioperative, beta blocker, surgery, and noncardiac. Inclusion criteria were randomized controlled trials evaluating perioperative beta blockade in noncardiac surgery. Studies were evaluated independently by 2 researchers. Cochrane Collaboration Software (Review Manager 4.2) was used to calculate relative risk (RR), risk difference (RD), and 95% confidence interval (CI). Six distinct postoperative adverse events were analyzed. RESULTS: Eligible studies included 6 randomized controlled trials evaluating perioperative beta blockade in patients undergoing noncardiac surgery. These studies evaluated a total of 632 patients: 354 received perioperative beta blockade and 278 did not. Results for the 6 postoperative outcomes are shown. [table: see text] The 2 largest effects were a decrease in long-term cardiac mortality from 12% to 2% and a decrease in myocardial ischemia from 33% to 15%. All outcomes except perioperative overall mortality had improvements (P < .02), which favor the use of perioperative beta blockade. CONCLUSIONS: This report highlights for the first time the aggregated risk reduction from all published randomized controlled trials, and shows the protection of perioperative beta blockade against both short-term complications and mortality.

Adrenergic beta-Antagonists↗

PubMed2004

An integrated method to determine meaningful changes in health-related quality of life.

OBJECTIVE: We describe an integrated method for determining meaningful change in health-related quality of life (HRQOL) that combines information from anchor-based and distribution-based methods and illustrate this method using data aggregated from weight loss studies. STUDY DESIGN AND SETTING: A total of 1476 participants in weight loss studies were evaluated at baseline and at 6 months using the Impact of Weight on Quality of Life-Lite (IWQOL-Lite). Severity of baseline impairment was determined by comparing scores with those obtained from a normative sample of 534 normal/overweight individuals. The precision of the IWQOL-Lite was evaluated using standard error of measurement corrected for regression to the mean. Weight loss was used as an anchor for evaluating changes in IWQOL-Lite scores. RESULTS: Change in HRQOL varied as a function of weight loss and baseline severity of HRQOL. Using this integrated method, an improvement of 7.7 to 12 points (depending on baseline severity) on IWQOL-Lite total score is considered meaningful. CONCLUSION: Meaningful change in HRQOL can be determined using an integrated method that (1) combines information from anchor-based and distribution-based methods, (2) reconciles discrepancies between these two methods, and (3) adjusts for baseline severity and regression to the mean. This method may be applied to other types of HRQOL measures and conditions.

Adult↗

PubMed2004

Increasing inequalities in premature mortality in Great Britain.

STUDY OBJECTIVE: To describe inequalities in all cause premature mortality between and within regions of Great Britain and how these inequalities have changed between 1979 and 1998. DESIGN: Retrospective study using routine population and death data aggregated into five year age and sex groups for each of 20 years. SETTING: All 459 local authority districts (England and Wales) and local government districts (Scotland). PARTICIPANTS: Estimated population and registered deaths aged 0-64. MAIN OUTCOME MEASURES: Indirectly standardised mortality ratios for all cause mortality; percentages of deaths that would be avoided if there were no inequalities between and within regions. RESULTS: The decrease in premature mortality of 36% seen in Great Britain ranged from 42% in Wales to 33% in Scotland and 31% in London. Differences between regions led to excess mortality of about 25% in Scotland, the North East, and the North West. In London excess mortality increased from 14% to 19%. Inequalities within regions increased in most parts of Great Britain, the exceptions being Wales, London, and the South West. The largest increase was seen in Scotland where the percentage of excess deaths increased from 23% to 33%. CONCLUSIONS: A decrease in premature mortality in Great Britain was seen in all regions, although less pronounced in London, but the gap between regions remained. Inequalities between districts within regions vary from one region to another and have increased in nearly every part of Great Britain.

Adolescent↗

PubMed2001

Material deprivation and leading causes of death by gender: evidence from a nationwide small area study.

STUDY OBJECTIVE: To investigate the association between material deprivation and 10 leading causes of death by gender. DESIGN: Small area cross sectional ecological study using two dimensions of material deprivation (Index 1 and Index 2) drawn from 1991 census and cause specific mortality data aggregated for 1987-1995. SETTING: 2218 small areas in Spain. MAIN RESULTS: Strong detrimental associations of two deprivation indices were found with top six leading causes of death for men and top seven leading causes of death for women, except breast cancer. For men, the highest percentages of excess mortality (between 40% and 60%) were found for smoking and alcohol related causes of death such as lung cancer, chronic obstructive pulmonary diseases, and cirrhosis while for women the highest percentages of excess mortality (between 40% and 60%) were found for diet related causes such as diabetes and ischaemic heart disease. CONCLUSIONS: Health inequality is a widespread phenomenon in the majority of the top leading causes of deaths of the nation. Increasing levels of deprivation indices are associated with mortality risk differently by both cause and gender. Results suggest that deprivation effects mainly captured by Index 2 may manifest largely as unfavourable health behaviours leading to gender specific sets of causes of deaths. Findings of this study are consistent with the idea that material deprivation determines health inequality through both an increase of general susceptibility to ill health, leading to excess mortality in a wide range of causes, and a set of specific factors, resulting in an increased risk of death from a specific set of causes in each gender.

Cause of Death↗

PubMed1999

Direct health care costs for treatment of diabetes mellitus and hypertension in an IPA-group-model HMO.

The differences in direct health care costs and use between HMO enrollees with both diabetes mellitus and hypertension and enrollees with either disease alone were studied. Two years' worth of medical and pharmacy claims data from a hybrid (independent practice association and group)-model HMO were evaluated. Diagnoses were determined from medical claims data and cross-referenced with prescription information from pharmacy claims data. Aggregate costs associated with each disease, including pharmacy costs, costs of physician office visits, and laboratory costs, were compiled. Comparisons were made of all costs (any cost incurred by the health plan for the member, regardless of disease) and disease-specific costs. The frequency of comorbid conditions was identified. A total of 6195 patients (670 with diabetes and hypertension, 1756 with diabetes alone, and 3769 with hypertension alone) were assessed. Patients with both diseases incurred much higher costs per year than patients with diabetes or hypertension alone (mean costs, $13,446, $8,493, and $8,424, respectively). Hospitalization costs contributed the greatest amount to total costs, while emergency room costs contributed the least. Disease-specific costs for diabetes and hypertension represented less than one quarter of total health care costs per patient. Average disease-specific costs were highest for patients with both diseases ($2,955), followed by costs for patients with hypertension alone ($1,803) and patients with diabetes alone ($689). The percentage spent on prescriptions was much higher for disease-specific costs than for total costs. The three most common comorbid conditions were dyslipidemia, coronary artery disease, and chronic obstructive pulmonary disease, with the frequency of cerebrovascular disease and myocardial infarction more than double in patients with diabetes and hypertension compared with patients with either disease alone. The cost of care for a patient with both diabetes and hypertension, although not double that for a patient with diabetes or hypertension alone, was higher than the cost of treating either disease.

Data Collection↗

PubMed2001

Non-linear dynamics of cardiovascular system in humans exposed to repetitive apneas modeling obstructive sleep apnea: aggregated time series data analysis.

OBJECTIVE: Testing the hypothesis that alterations in non-linear dynamics of the cardiovascular variability appear in healthy, awake subjects during voluntary apnea. SUBJECTS AND METHODS: Ten young subjects performed 20 apneas 60 s each separated by 1 min free breathing. Inter-beat interval (IBI) measured as RR-interval in ECG, systolic (SYS) and diastolic (DIAS) arterial blood pressure. stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) were non-invasively recorded and computed by Portapress 2 system. Correlation dimension according to Grassberger-Proccacia algorithm (CD) and ratio of % determinism versus % recurrence (RDR) computed from recurrence plot according to Webber and Zbiluth [J. Appl. Physiol. 76 (1994) 965] were used as the indices of chaos and complexity. Sequential time series of cardiovascular variables in consecutive 60-s apneas and inter-apnea free breathings were separately windowed and aggregated. CD and RDR of aggregated apneic time series were compared with CD and RDR values of aggregated time series of inter-apnea free breathing, 10 min at rest and 10 min recovery. Reliability of the aggregation method of sequential time series was tested on transformed simulated data generated by Lorenz model. Error in CD and RDR estimation did not exceed 5% and 1%. respectively. RESULTS: CD of cardiovascular variables computed from aggregated apneas was significantly reduced and RDR augmented versus control and recovery periods. CD and RDR values of inter-apnea phases were in between those in control and during apneas. Time domain linear variance (SD) was increased during aggregated apneas. CONCLUSIONS: Signal dynamics dependent windowing and data aggregation could be a useful tool for non-linear analysis of short repeatable sequential time series; time domain linear variability of the cardiovascular dynamics is augmented while complexity reduced during apneic chemoreceptor stimulation; alterations in non-linear dynamics of cardiovascular variables during apneas in healthy normotensive subjects may suggest an early sign of a mechanism implicated in arterial hypertension in OSAS.

Adult↗

PubMed2003

The cost-effectiveness of hearing-aid fitting in the Netherlands.

OBJECTIVE: To determine the cost-effectiveness of hearing-aid fitting. DESIGN: Cost-effectiveness analysis using a Markov model based on aggregate data and results from a prospective intervention study. SETTING: The cost-effectiveness study was based in the general community. The prospective study was hospital based, as 85% of the first-time hearing-aid users attend a hospital in the process of hearing-aid fitting. PATIENTS: The prospective intervention study included adult first-time hearing-aid users with no contraindications for hearing-aid use. INTERVENTION: The usual process of hearing-aid fitting in the Netherlands. MAIN OUTCOME MEASURE: Costs per quality-adjusted life-year (QALY). The QALYs were based on EuroQol scores. We included direct and indirect costs in the analysis. RESULTS: The mean improvement on the EuroQol measure was 0.03 (95% confidence interval [CI], -0.03 to 0.08), and on the hearing-specific visual analog scale, 0.27 (95% CI, 0.22-0.31). The base-case outcome based on the EuroQol was 15 807/QALY (US dollars 17 072/QALY) (CI, -24 239/QALY to 3718/QALY). CONCLUSIONS: On the basis of this base-case estimate, fitting of hearing aids is considered a cost-effective health care intervention. The CI indicates that the result is not unambiguously positive, probably because the EuroQol lacked sensitivity for the evaluation of hearing-aid fitting. Until now, no study has found an effect of hearing-aid fitting on generic quality of life. Therefore, measures are needed that are suitable for the evaluation of the effects of interventions for sensory disabilities, such as the fitting of hearing aids, on generic quality of life.

Adult↗

PubMedDate not supplied

Statistical power and design of focused clustering studies.

Focused clustering studies investigate raised incidence of disease in the vicinity of prespecified putative sources of increased risk. The analytic power functions of three focused tests of disease clustering are defined and used to address two design issues related to focused cluster studies. The power functions provide sample sizes required to detect a given increase in relative risk and allow measurement of the effects of aggregating data when a fixed underlying cluster model is assumed. Results are illustrated on hypothetical data as well as leukaemia data from upstate New York.

Cluster Analysis↗

PubMed1998

Autoradiographic and SPECT imaging of cerebral opioid receptors with an iodine-123 labeled analogue of diprenorphine.

The feasibility of imaging cerebral opioid receptors by single photon emission computed tomography (SPECT) has been established in baboon using a novel analog of diprenorphine (DPN) radiolabeled with iodine-123. The radioligand, [123I]-O-IA-DPN (C6-O-[123I]iodoallyl-DPN), was prepared in good yield (80%) with high radiochemical purity (>97%) and high specific radioactivity (>2,400 mCi/micromol). In ex vivo autoradiographic studies, with and without naltrexone blockade, [123I]-O-IA-DPN specifically labeled opioid receptors throughout the mouse brain. Nonmetabolized radioligand accounted for >90% of the signal observed in extracts of whole mouse brain. SPECT imaging trials showed that [123I]-O-IA-DPN selectively localized in regions of baboon brain known to have high densities of opioid receptors, such as striatum, thalamus, and temporal cortex. A much lower level of radioligand uptake and retention was noted for cerebellum, a region with few opioid binding sites. Pretreatment with naltrexone (6.5 pmol/kg) blocked [123I]-O-IA-DPN binding in all brain regions. Using naltrexone blockade to define the nonspecific component for a given region of interest, total to nonspecific binding ratios increased linearly (r > or = 0.98) over the SPECT study with maximal values for striatum (9.8), thalamus (7.1), and temporal cortex (6.9) reached at the last time point investigated (3.5 h). Specific binding for these regions, assessed as the difference between regional SPECT activity for the control and blocked states, proved irreversible over the observation period. By the end of the time course, specific [123I]-O-IA-DPN binding was >85% of total radioactivity in regions rich in opioid receptors and 62% of total radioactivity in cerebellum. The aggregate data are consistent with visualization of multiple opioid receptor types. Thus, [123I]-O-IA-DPN should prove useful for SPECT studies within the constraints imposed by a lack of innate selectivity for a single type of brain opioid receptor.

Animals↗

PubMed1988

Caffeine ingestion and breast cancer. A negative correlation.

The potential association of breast cancer and caffeine intake was examined using international aggregate data. Death rates from breast cancer were correlated with caffeine ingestion from tea and coffee sources in 44 countries. By using multiple regression analysis, the authors demonstrated that 85% of the international variation in breast cancer rates is associated with variations in fat intake. When this is accounted for, the partial correlation of breast cancer rates with caffeine intake is negative (and significant at P less than 0.05). When the data are weighted by populations in each country, the negative partial correlation of caffeine with breast cancer disappears, but the strong positive association with fat intake remains unchanged. Although there have been suggestions that caffeine exacerbates fibrocystic disease of the breast and may be a causal factor in breast cancer, data from this study do not support a positive association between caffeine intake and subsequent development of breast cancer.

Breast Neoplasms↗

PubMed2000

Role of smoking and diet in the cross-cultural variation in lung-cancer mortality: the Seven Countries Study. Seven Countries Study Research Group.

We examined the role of smoking and diet in the cross-cultural variation in lung-cancer mortality, using aggregated data of the Seven Countries Study, a follow-up study comprising 12,763 middle-aged men in 16 cohorts in Europe, the United States and Japan, which started around 1960. Smoking habits were assessed with a standardised questionnaire. Dietary intake was collected in random sub-samples of each cohort by the dietary record method. Cohort-specific 25-year lung-cancer mortality among all men and among categories of smoking behaviour was related to smoking prevalence and population average dietary intake, respectively, using Poisson regression. Smoking prevalence was positively associated with lung-cancer mortality [risk ratio 1.47, 95% confidence interval (CI) 1.05-2.07, for an increase of 10 percentage points]. Lung-cancer mortality among smokers, which varied significantly among cultures, was positively associated with average fat intake, especially saturated fat intake (rate ratio 1.10, 95% CI 1.04-1.17, for an increase of 4.6 g) but not with unsaturated fat intake. Average fruit and vegetable intake were not related to lung-cancer mortality. Among never-smokers, the power to detect associations was low. In conclusion, both smoking prevalence and average fat intake, especially saturated fat, may play a role in the cross-cultural variation in lung-cancer mortality, either independently or by effect modification.

Adult↗

PubMed1984

Etiological hypotheses in schizophrenia: cross-level analysis.

Used the multicausal hypothesis generation capabilities of multiple regression analysis of aggregate data to explore the complex etiology of schizophrenia. Attendant dangers of ecological inference are controlled by combining regression analysis with individual-level analysis of the same population. The resulting cross-level analysis adds a new dimension to our understanding.

Adult↗

PubMed1992

Consanguineous marriage in Jordan.

We conducted a population-based study of consanguineous marriages in Jordan. About two thousand households were interviewed. First cousin marriages were encountered in 32.03%, second cousin in 6.8%, distant relation in 10.5%, and no relation in 50% of all marriages, respectively. Inbreeding coefficients were compared with those of other countries. The most important variables affecting inbreeding were social tradition, religion, education, and place of residence--urban vs. rural. Secular trends appear rather stable since the early decades of the twentieth century, especially for first cousin marriages. Jordan society showed a deeply rooted traditional behavioral pattern when inbreeding is considered.

Adult↗

PubMed2005

Clinical impact and frequency of anatomic pathology errors in cancer diagnoses.

BACKGROUND: To the authors' knowledge, the frequency and clinical impact of errors in the anatomic pathology diagnosis of cancer have been poorly characterized to date. METHODS: The authors examined errors in patients who underwent anatomic pathology tests to determine the presence or absence of cancer or precancerous lesions in four hospitals. They analyzed 1 year of retrospective errors detected through a standardized cytologic-histologic correlation process (in which patient same-site cytologic and histologic specimens were compared). Medical record reviews were performed to determine patient outcomes. The authors also measured the institutional frequency, cause (i.e., pathologist interpretation or sampling), and clinical impact of diagnostic cancer errors. RESULTS: The frequency of errors in cancer diagnosis was found to be dependent on the institution (P < 0.001) and ranged from 1.79-9.42% and from 4.87-11.8% of all correlated gynecologic and nongynecologic cases, respectively. A statistically significant association was found between institution and error cause (P < 0.001); the cause of errors resulting from pathologic misinterpretation ranged from 5.0-50.7% (the remainder were due to clinical sampling). A statistically significant association was found between institution and assignment of the clinical impact of error (P < 0.001); the aggregated data demonstrated that for gynecologic and nongynecologic errors, 45% and 39%, respectively, were associated with harm. The pairwise kappa statistic for interobserver agreement on cause of error ranged from 0.118-0.737. CONCLUSIONS: Errors in cancer diagnosis are reported to occur in up to 11.8% of all reviewed cytologic-histologic specimen pairs. To the authors' knowledge, little agreement exists regarding whether pathology errors are secondary to misinterpretation or poor clinical sampling of tissues and whether pathology errors result in serious harm.

Diagnostic Errors↗

PubMed2005

Waiting lists, waiting times and admissions: an empirical analysis at hospital and general practice level.

We report an empirical analysis of the responses of the supply and demand for secondary care to waiting list size and waiting times. Whereas previous empirical analyses have used data aggregated to area level, our analysis focuses on the supply responses of a single hospital and the demand responses of the GP practices it serves, and distinguishes between first outpatient visits, inpatient admissions, day-case treatment and emergency admissions. The results are plausible and in line with the theoretical model. For example: the demand from practices for first outpatient visits is negatively affected by waiting times and distance to the hospital. Increases in waiting times and waiting lists lead to increases in supply; the supply of elective inpatient admissions is affected negatively by current emergency admissions and positively by lagged waiting list and waiting time. We use the empirical results to investigate the dynamic responses to one off policy measures to reduce waiting times and lists by increasing supply.

Health Services Needs and Demand↗

PubMed2006

Matching estimates of the impact of over-the-counter emergency birth control on teenage pregnancy.

In this paper, we demonstrate how matching estimators can be used to evaluate policy interventions which are implemented in relatively few regions at different times. Our technique is based on translating calendar time into 'experimental time' to provide a common starting point for entry by different areas into the scheme. Such an approach is likely to have many applications, in particular to cases of state- or country-level interventions for which only aggregate data are available. We illustrate the technique using the case of free over-the-counter access to emergency birth control for teenagers at pharmacies in England. We construct matching estimates of the impact of this scheme on the under-18 conception rate in local authorities. Irrespective of either the matching or the adjustment procedure, we find no evidence that over-the-counter emergency birth control schemes lead to lower teenage pregnancy rates.

Adolescent↗

PubMed2007

An empirical analysis of US and Japanese health insurance using age-period-cohort decomposition.

Aggregate data on household health insurance expenditure in the US and Japan that are classified by period and age are decomposed into age, period, and cohort effects by using the Bayesian cohort models. These models are developed to overcome the identification problem involved in cohort analysis. Despite the differences between the health insurance systems of the two countries, three interesting empirical findings are obtained. First, in both the countries, the age effects are the most influential, and the cohort effects have negligible influence. The latter provides a striking policy implication since the generational imbalance in social security expenditures is widely recognized in developed countries. Second, in both the countries, the period effects show a roughly upward trend. Finally, the age effects exhibit a roughly upward movement for all age groups in the US; however, in Japan, these effects show a downward movement for the 55-59 age group due to the changes in the health insurance system on retirement.

Adult↗