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Results for “Demographic modelling”

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PubMed1998

Hormonal contraception, sexually transmitted diseases, and risk of heterosexual transmission of human immunodeficiency virus type 1.

To examine associations between method of contraception, sexually transmitted diseases (STDs), and incident human immunodeficiency virus type 1 (HIV-1) infection, a prospective observational cohort study was done among female sex workers attending a municipal STD clinic in Mombasa, Kenya. Demographic and behavioral factors significantly associated with HIV-1 infection included type of workplace, condom use, and parity. In multivariate models, vulvitis, genital ulcer disease, vaginal discharge, and Candida vaginitis were significantly associated with HIV-1 seroconversion. Women who used depo medroxyprogesterone acetate (DMPA) had an increased incidence of HIV-1 infection (hazard ratio [HR], 2.2; 95% confidence interval [CI], 1.4-3.4). In a multivariate model controlling for demographic and exposure variables and biologic covariates, the adjusted HR for HIV-1 infection among DMPA users was 2.0 (CI, 1.3-3.1). There was a trend for an association between use of high-dose oral contraceptive pills and HIV-1 acquisition (HR, 2.6; CI, 0.8-8.5).

Behavior↗

PubMed2003

The role of community services and informal support on five-year drinking trajectories of alcohol dependent and problem drinkers.

OBJECTIVE: The purpose of this study was to examine how informal support and community services impact the course of alcohol disorders by examining the trajectories of alcohol consumption over 5 years in dependent and problem drinkers. METHOD: Alcohol dependent adults (n = 600) and problem drinkers (n = 992) were identified through probability surveys in the general population and in public and private treatment programs throughout a California county. Participants were interviewed at baseline and again 1, 3 and 5 years later. Models controlling for demographic characteristics, problem severity, community services and recovery-oriented social networks were estimated, using a multi-level, mixed model to predict alcohol consumption over time. RESULTS: A significant trend of reduced drinking over time was observed for both dependent and problem drinkers. Recovery-oriented social networks and AA participation predicted decreased consumption for both groups. Contacts with medical, mental health, welfare and legal systems were predictive of reduced consumption for problem drinkers. In the dependent group, only contacts with mental health agencies marginally predicted decreased consumption. CONCLUSIONS: Findings point to the importance of developing mechanisms for better identifying problem drinkers in the course of contacts with health and social service systems and for facilitating use of self-help groups and positive changes in social networks. Development of recovery-oriented social networks should be emphasized to extend the benefits of treatment for dependent individuals.

Adult↗

PubMed2005

The health belief model, sexual behaviors, and HIV risk among Taiwanese immigrants.

In this first investigation of Taiwanese sexual behaviors in the United States, 144 Taiwanese students completed an online anonymous survey. Demographics, health belief model (HBM) constructs, and acculturation were examined as predictors of sexual behaviors over the last year. Analyses indicated that participants who reported a higher number of sexual partners and more frequent sexual intercourse tended to be more educated and more likely to be nonheterosexual. The HBM constructs, as a set, reliably predicted participants' sexual behaviors. Self-efficacy was the strongest predictor within the HBM. Furthermore, acculturation moderated the predictive power of the HBM with respect to intercourse frequency. The main limitation of the study is that the measure of HBM, which was not designed to target Asian immigrants, was psychometrically poor. The results suggest self-efficacy is a target for behavioral change, acculturation may need to be incorporated into the HBM, and more culturally sensitive measures need to be developed.

Acculturation↗

PubMed2003

Development of a risk-adjusted capitation model based on principal inpatient diagnoses in Taiwan.

BACKGROUND AND PURPOSE: Taiwan's National Health Insurance (NHI) program has considered the use of capitation payments to health care providers as a method for control of the rising costs of the system. The establishment of capitation payments usually requires the performance of risk adjustment. The purposes of this study were to develop a diagnosis-based risk adjustment model for the NHI and to evaluate its predictability. METHODS: Using a 2% random sample of 371,620 NHI enrollees, the authors developed a Taiwan version of the Principal Inpatient Diagnosis Cost Groups (TPIPDCGs) from 1996 claim records to predict an individual's expenditure in 1997. Weighted least squares regression models were built in an estimation sample (two-thirds of the study sample), and were cross-validated in a validation sample (the remaining one-third of the study sample). Predictive R2 and predictive ratios were used to evaluate the model's predictability. RESULTS: Only 7.88% of the study sample could be classified into 1 of the 16 TPIPDCGs. Combined with demographic variables, which alone could explain 3.7% of the variation in an individual's future expenditure, the risk adjustment model based on TPIPDCGs could explain 12.2% of expenditure variation. In addition, the finding that the predictive ratios of the TPIPDCG model approximated unity better than those of the demographic model in all subgroups indicates that the capitation payment as predicted by the TPIPDCG model for each subgroup would better correlate to the actual spending. CONCLUSION: Taiwan's risk-adjusted capitation model based on principal inpatient diagnoses has higher predictability on individual's future expenditure than its counterpart in the USA. This finding provides insight into not only the development of Taiwan's diagnosis-based risk adjustment models but also the necessity of modification when applying foreign-developed risk adjustment models to the NHI.

Capitation Fee↗

PubMed1982

Demographic disaggregation in the construction of regional econometric models: a statistical evaluation.

"A cohort-component method is used to construct historical annual age/sex disaggregations of total population. In econometric models of six substate areas [in the United States], regressions are estimated with and without the disaggregated data for five model variables expected to be dependent on the size of particular population subgroups. Statistical tests are performed to determine significant differences in residual variance of estimation with and without the disaggregated data. Although age/sex population projections may be a desired model output per se, the results indicate that the population subgroup data generally do not improve estimation of other model variables." (summary in FRE, ITA, JPN, )

Age Distribution↗

PubMed2003

The Depression Anxiety Stress Scales (DASS): normative data and latent structure in a large non-clinical sample.

OBJECTIVES: To provide UK normative data for the Depression Anxiety and Stress Scale (DASS) and test its convergent, discriminant and construct validity. DESIGN: Cross-sectional, correlational and confirmatory factor analysis (CFA). METHODS: The DASS was administered to a non-clinical sample, broadly representative of the general adult UK population (N = 1,771) in terms of demographic variables. Competing models of the latent structure of the DASS were derived from theoretical and empirical sources and evaluated using confirmatory factor analysis. Correlational analysis was used to determine the influence of demographic variables on DASS scores. The convergent and discriminant validity of the measure was examined through correlating the measure with two other measures of depression and anxiety (the HADS and the sAD), and a measure of positive and negative affectivity (the PANAS). RESULTS: The best fitting model (CFI =.93) of the latent structure of the DASS consisted of three correlated factors corresponding to the depression, anxiety and stress scales with correlated error permitted between items comprising the DASS subscales. Demographic variables had only very modest influences on DASS scores. The reliability of the DASS was excellent, and the measure possessed adequate convergent and discriminant validity Conclusions: The DASS is a reliable and valid measure of the constructs it was intended to assess. The utility of this measure for UK clinicians is enhanced by the provision of large sample normative data.

Adolescent↗

PubMed1990

A causal model describing the relationship of women's postpartum health to social support, length of leave, and complications of childbirth.

Recovery from childbirth is a complex process that may involve not only the gynecological organs, but also the cardiovascular, respiratory, musculo-skeletal, urologic, gastrointestinal, endocrine, and nervous systems. The process of postpartum recovery may span several months and is related to a variety of personal, family, and social variables. This paper presents a model that describes changes in women's health over the first postpartum year and the relationship between health changes and other variables. The model's dependent variables--mothers' mental and physical health--have a reciprocal effect on one another. The independent variables within the model include length of maternity leave, social support, complications of childbirth, baby's health, mother's use of cigarettes and alcohol, and demographic characteristics. This model is proposed as a research tool for future investigations in postpartum health, and as a conceptual framework to enhance our understanding of the relationship between postpartum health and other important variables.

Adult↗

PubMed1992

Lower back pain. Laminectomies, spinal fusions, demographics, and socioeconomics.

The models and analyses used in this study represent an important step in the continued search for the optimum use of surgery for the treatment of lower back pain. The likelihood of patients who are hospitalized with lower back pain in Massachusetts receiving either laminectomies or spinal fusions or both was increased when any of the following demographic, socioeconomic, or medical characteristics were present: white, male, well insured, young, routine admission, admitted to a medium-sized hospital, admitted to a teaching hospital, admitted to a hospital with a high occupancy rate, and discharged home.

Back Pain↗

PubMed2001

Risk adjustment alternatives in paying for behavioral health care under Medicaid.

OBJECTIVE: To compare the performance of various risk adjustment models in behavioral health applications such as setting mental health and substance abuse (MH/SA) capitation payments or overall capitation payments for populations including MH/SA users. DATA SOURCES/STUDY DESIGN: The 1991-93 administrative data from the Michigan Medicaid program were used. We compared mean absolute prediction error for several risk adjustment models and simulated the profits and losses that behavioral health care carve outs and integrated health plans would experience under risk adjustment if they enrolled beneficiaries with a history of MH/SA problems. Models included basic demographic adjustment, Adjusted Diagnostic Groups, Hierarchical Condition Categories, and specifications designed for behavioral health. PRINCIPAL FINDINGS: Differences in predictive ability among risk adjustment models were small and generally insignificant. Specifications based on relatively few MH/SA diagnostic categories did as well as or better than models controlling for additional variables such as medical diagnoses at predicting MH/SA expenditures among adults. Simulation analyses revealed that among both adults and minors considerable scope remained for behavioral health care carve outs to make profits or losses after risk adjustment based on differential enrollment of severely ill patients. Similarly, integrated health plans have strong financial incentives to avoid MH/SA users even after adjustment. CONCLUSIONS: Current risk adjustment methodologies do not eliminate the financial incentives for integrated health plans and behavioral health care carve-out plans to avoid high-utilizing patients with psychiatric disorders.

Adult↗

PubMed1984

Systematic temporal changes in host susceptibility to infection: demographic mechanisms.

Simple mathematical models are developed to examine the influence of variability in host susceptibility to infection, on the dynamics of host-parasite population interactions. When hosts differ in their innate susceptibility (at birth), to infection by a specific parasite, the average susceptibility of the host population as a whole may show systematic changes through time. Such patterns may arise as a result of demographic factors associated with the interaction between host and parasite populations, in the absence of inheritance mechanisms (a genetic component) or acquired resistance (an immunological component). The general significance of this observation is discussed in terms of the coevolution of host-parasite associations.

Animals↗

PubMed2000

Mathematical elements of attack risk analysis for mountain pine beetles.

Three different mathematical approaches are combined to develop a spatial framework in which risk of mountain pine beetle (MPB) attack on individual hosts may be assessed. A density-based partial differential equation model describes the dispersal and focusing behavior of MPB. A local projection onto a system of ordinary differential equations predicts the consequences of the density equations at individual hosts. The bifurcation diagram of these equations provides a natural division into categories of risk for each host. A stem-competition model links host vigor to stand age and demographics. Coupled together, these models illuminate spatial risk structures which may also shed light on the role of climatic variables in population outbreaks. Preliminary results suggest that stand microclimate has much greater influence on risk of attack than host vigor and stand age.

Animals↗

PubMed1991

Self-report of physical activity and patterns of mortality in Seventh-Day Adventist men.

The Adventist Mortality Study provides 26-year follow-up through 1985 for 9484 males who completed a lifestyle questionnaire in 1960. The relationship of self-reported physical activity and all cause and disease-specific mortality was examined by survival analysis and with the Cox proportional hazards model, controlling for demographic and lifestyle characteristics. Moderate activity was associated with a protective effect on cardiovascular and all cause mortality in both analyses. In the Cox model, age-specific estimates of relative risk (RR) were obtained for several endpoints due to a significant interaction between level of physical activity and attained age (age at death or end of follow-up). This model permits calculation of the age at which the RR = 1.0, or the age at crossover of risk. For moderate activity, this age was 95.6 years (95% confidence intervals, 81.7-109.4 years) for all cause mortality and 91.5 years (95% confidence intervals, 79.0-104.0 years) for cardiovascular mortality. While the protective effect on mortality associated with moderate activity decreased with increasing age, it remained significant to the verge of the present life span.

Adult↗

PubMed2003

Prediction of mortality from catastrophic burns in children.

BACKGROUND: We previously developed a model to predict survival in massive paediatric burns (>80% total body surface area [TBSA]). This model included not only demographic variables, but also variables obtained throughout the hospital course. We aimed to prospectively validate our model for accuracy of outcome prediction. METHODS: We admitted 33 paediatric burn patients with burns greater than 80% TBSA. We recorded age, burn size, inhalation injury, resuscitation, packed-cell volume at admission, base deficit, serum osmolarity, sepsis, inotropic support, platelet count, creatinine, and ventilator dependency. We entered these data into our previous models. RESULTS: 20 male and 13 female children with mean age 7.6 (SD 1) years with TBSA burns of 88% (SD 1; full thickness 86% [SD 1]) were admitted. Mortality was 39.4% (13 of 30). When all variables were integrated into our final model, we predicted outcome with 97% accuracy. When we used a model based only on demographic characteristics of age, burn size, and presence of inhalation injury, outcome was correctly predicted in only 51% of patients. CONCLUSION: We show prospectively that mortality in severely burned children can be reliably estimated at a burn centre, and that outcome cannot be reliably predicted on the basis of demographic and injury characteristics alone. These data suggest that all severely burned children should be given a course of treatment before consideration of treatment futility.

Adolescent↗

PubMed2001

Cooperation in the dark: signalling and collective action in quorum-sensing bacteria.

The study of quorum-sensing bacteria has revealed a widespread mechanism of coordinating bacterial gene expression with cell density. By monitoring a constitutively produced signal molecule, individual bacteria can limit their expression of group-beneficial phenotypes to cell densities that guarantee an effective group outcome. In this paper, we attempt to move away from a commonly expressed view that these impressive feats of coordination are examples of multicellularity in prokaryotic populations. Here, we look more closely at the individual conflict underlying this cooperation, illustrating that, even under significant levels of genetic conflict, signalling and resultant cooperative behaviour can stably exist. A predictive two-trait model of signal strength and of the extent of cooperation is developed as a function of relatedness (reflecting multiplicity of infection) and basic population demographic parameters. The model predicts that the strength of quorum signalling will increase as conflict (multiplicity of infecting strains) increases, as individuals attempt to coax more cooperative contributions from their competitors, leading to a devaluation of the signal as an indicator of density. Conversely, as genetic conflict increases, the model predicts that the threshold density for cooperation will increase and the subsequent strength of group cooperation will be depressed.

Bacterial Physiological Phenomena↗

PubMed2004

A comparison of olanzapine and risperidone on the risk of psychiatric hospitalization in the naturalistic treatment of patients with schizophrenia.

BACKGROUND: Decreasing hospital admissions is important for improving outcomes for people with schizophrenia and for reducing cost of hospitalization, the largest expenditure in treating this persistent and severe mental illness. This prospective observational study compared olanzapine and risperidone on one-year psychiatric hospitalization rate, duration, and time to hospitalization in the treatment of patients with schizophrenia in usual care. METHODS: We examined data of patients newly initiated on olanzapine (N = 159) or risperidone (N = 112) who continued on the index antipsychotic for at least one year following initiation. Patients were participants in a 3-year prospective, observational study of schizophrenia patients in the US. Outcome measures were percent of hospitalized patients, total days hospitalized per patient, and time to first hospitalization during the one-year post initiation. Analyses employed a generalized linear model with adjustments for demographic and clinical variables. A two-part model was used to confirm the findings. Time to hospitalization was measured by the Kaplan-Meier survival formula. RESULTS: Compared to risperidone, olanzapine-treated patients had significantly lower hospitalization rates, (24.1% vs. 14.4%, respectively, p = 0.040) and significantly fewer hospitalization days (14.5 days vs. 9.9 days, respectively, p = 0.035). The mean difference of 4.6 days translated to $2,502 in annual psychiatric hospitalization cost savings per olanzapine-treated patient, on average. CONCLUSIONS: Consistent with prior clinical trial research, treatment-adherent schizophrenia patients who were treated in usual care with olanzapine had a lower risk of psychiatric hospitalization than risperidone-treated patients. Lower hospitalization costs appear to more than offset the higher medication acquisition cost of olanzapine.

Journal Article↗

PubMed2000

Diabetes is an independent risk factor for in-hospital mortality from acute spontaneous intracerebral hemorrhage.

OBJECTIVE: We tested the hypothesis that diabetes is an independent determinant of outcome after intracerebral hemorrhage (ICH). RESEARCH DESIGN AND METHODS: This was a hospital-based prospective study The setting was an acute care 350-bed hospital in the city of Barcelona, Spain. Spontaneous ICH was diagnosed in 229 (11%) of 2,000 consecutive stroke patients included in a prospective stroke registry during a 10-year period. Main outcome measures were frequency of demographic variables, risk factors, clinical events, neuroimaging data, and outcome in ICH patients with and without diabetes. Variables related to vital status at discharge (alive or dead) in the univariate analysis plus age were studied in 4 logistical regression models. RESULTS: A total of 35 patients (15.3%) had diabetes. The overall in-hospital mortality rate was 54.3% in the diabetic group and 26.3% in the nondiabetic group (P < 0.001). Previous cerebral infarction, altered consciousness, sensory symptoms, cranial nerve palsy, multiple topography of the hematoma, intraventricular hemorrhage, and infectious complications were significantly more frequent in diabetic patients than in nondiabetic patients. The presence of diabetes was a significant predictive variable in the model based on demographic variables and cardiovascular risk factors (odds ratio 2.98 [95% CI 1.37-6.46]) and in the models based on these variables plus clinical variables (5.76 [2.01-16.51]), neuroimaging variables (5.59 [1.87-16.691), and outcome data (6.10 [2.04-18.291). CONCLUSIONS: Diabetes is an independent determinant of death after ICH. ICH in diabetic individuals presents some different clinical features compared with ICH in nondiabetic patients.

Aged↗

PubMed2003

Racial disparity in cardiac procedures and mortality among long-term survivors of cardiac arrest.

BACKGROUND: It is unknown whether white and black Medicare beneficiaries have different rates of cardiac procedure utilization or long-term survival after cardiac arrest. METHODS AND RESULTS: A total of 5948 elderly Medicare beneficiaries (5429 white and 519 black) were identified who survived to hospital discharge between 1990 and 1999 after admission for cardiac arrest. Demographic, socioeconomic, and clinical information about these patients was obtained from Medicare administrative files, the US census, and the American Hospital Association's annual institutional survey. A Cox proportional hazard model that included demographic and clinical predictors indicated a hazard ratio for mortality of 1.30 (95% CI 1.09 to 1.55) for blacks aged 66 to 74 years compared with whites of the same age. The addition of cardiac procedures to this model lowered the hazard ratio for blacks to 1.23 (95% CI 1.03 to 1.46). In analyses stratified by race, implantable cardioverter-defibrillators (ICDs) had a mortality hazard ratio of 0.53 (95% CI 0.45 to 0.62) for white patients and 0.50 (95% CI 0.27 to 0.91) for black patients. Logistic regression models that compared procedure rates between races indicated odds ratios for blacks aged 66 to 74 years of 0.58 (95% CI 0.36 to 0.94) to receive an ICD and 0.50 (95% CI 0.34 to 0.75) to receive either revascularization or an ICD. CONCLUSIONS: There is racial disparity in long-term mortality among elderly cardiac arrest survivors. Both black and white patients benefited from ICD implantation, but blacks were less likely to undergo this potentially life-saving procedure. Lower rates of cardiac procedures may explain in part the lower survival rates among black patients.

Aged↗

PubMedDate not supplied

Discomfort and disability in upper respiratory tract infection.

Ambulatory patients with upper respiratory infection were studied to determine the relative contributions made by tissue pathology, psychologic and perceptual attributes, and demographic characteristics to reported discomfort and disability. Patients (n = 115) attending a medical walk-in clinic completed self-report questionnaires to assess somatization, anxiety, depression, hostility, amplification, discomfort, disability, and demographic characteristics. Clinicians rated the extent of disease apparent on physical examination. Using stepwise multiple regression, demographic factors and physical findings explained 25% of the variance in reported discomfort. The addition of somatization scores increased the variance explained to 49%. The best model, including somatization and amplification, accounted for 54% of the variance. A model composed of demographic characteristics, physical findings, and somatization accounted for 25% of the variance in reported disability. The authors conclude that psychologic variables are important in the experience of discomfort, even after the extent of physical disease and demographic characteristics have been taken into account.

Activities of Daily Living↗