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Computerized health information and the demand for medical care.

OBJECTIVE: Consumer health information, once the domain of books and booklets, has become increasingly digitized and available on the Internet. This study assessed the effect of using computerized health information on consumers' demand for medical care. METHODS: The dependent variable was self-reported number of visits to the doctor in the past year. The key independent variable was the use of computerized health information, which was treated as endogenous. We tested the effect of using computerized health information on physician visits using ordinary least squares, instrumental variables, fixed effects, and fixed-effects instrumental variables models. The instrumental variables included exposure to the Healthwise Communities Project, a community-wide health information intervention; computer ownership; and Internet access. Random households in three cities were mailed questionnaires before and after the Healthwise Communities Project. In total, 5909 surveys were collected for a response rate of 54%. RESULTS: In both the bivariate and the multivariate analyses, the use of computerized health information was not associated with self-reported entry into care or number of visits. The instrumental variables models also found no differences, with the exception that the probability of entering care was significantly greater with the two-stage conditional logit model (P <.05). CONCLUSIONS: Although providing people with health information is intuitively appealing, we found little evidence of an association between using a computer for health information and self-reported medical visits in the past year. This study used overall self-reported utilizations as the dependent variable, and more research is needed to determine whether health information affects the health production function in other important ways, such as the location of care, the timing of getting care, or the intensity of treatment.

Adolescent↗

The effect of private insurance on the health of older, working age adults: evidence from the health and retirement study.

OBJECTIVE: Primarily, to determine if the presence of private insurance leads to improved health status, as measured by a survey-based health score. Secondarily, to explore sensitivity of estimates to adjustments for endogeneity. The study focuses on adults in late middle age who are nearing entry into Medicare. DATA SOURCES: The analysis file is drawn from the Health and Retirement Study, a national survey of relatively older adults in the labor force. The dependent variable, an index of 5 health outcome items, was obtained from the 1996 survey. Independent variables were obtained from the 1992 survey. State-level instrumental variables were obtained from the Area Resources File and the TAXSIM file. The final sample consists of 9,034 individuals of which 1,540 were uninsured. STUDY DESIGN: Estimation addresses endogeneity of the insurance participation decision in health score regressions. In addition to ordinary least squares (OLS), two models are tested: an instrumental variables (IV) model, and a model with endogenous treatment effects due to Heckman (1978). Insurance participation and health behaviors enter with a lag to allow their effects to dissipate over time. Separate regressions were run for groupings of chronic conditions. PRINCIPAL FINDINGS: The OLS model results in statistically significant albeit small effects of insurance on the computed health score, but the results may be downward biased. Adjusting for endogeneity using state-level instrumental variables yields up to a six-fold increase in the insurance effect. Results are consistent across IV and treatment effects models, and for major groupings of medical conditions. The insurance effect appears to be in the range of about 2-11 percent. There appear to be no significant differences in the insurance effect for subgroups with and without major chronic conditions. CONCLUSIONS: Extending insurance coverage to working age adults may result in improved health. By conjecture, policies aimed at expanding coverage to this population may lead to improved health at retirement and entry to Medicare, potentially leading to savings. However, further research is needed to determine whether similar results are found when alternative measures of overall health or health scores are used. Future research should also explore the use of alternative instrumental variables. Preliminary results provide no justification for targeting certain subgroups with susceptibility to certain chronic conditions rather than broad policy interventions.

Chronic Disease↗

Instruments for causal inference: an epidemiologist's dream?

The use of instrumental variable (IV) methods is attractive because, even in the presence of unmeasured confounding, such methods may consistently estimate the average causal effect of an exposure on an outcome. However, for this consistent estimation to be achieved, several strong conditions must hold. We review the definition of an instrumental variable, describe the conditions required to obtain consistent estimates of causal effects, and explore their implications in the context of a recent application of the instrumental variables approach. We also present (1) a description of the connection between 4 causal models-counterfactuals, causal directed acyclic graphs, nonparametric structural equation models, and linear structural equation models-that have been used to describe instrumental variables methods; (2) a unified presentation of IV methods for the average causal effect in the study population through structural mean models; and (3) a discussion and new extensions of instrumental variables methods based on assumptions of monotonicity.

Bias↗

Alcohol consumption, beverage prices and measurement error.

OBJECTIVE: Alcohol price data collected by the American Chamber of Commerce Researchers Association (ACCRA) have been widely used in studies of alcohol consumption and related behaviors. A number of problems with these data suggest that they contain substantial measurement error, which biases conventional statistical estimators toward a finding of little or no effect of prices on behavior. We test for measurement error, assess the magnitude of the bias and provide an alternative estimator that is likely to be superior. METHOD: The study utilizes data on per capita alcohol consumption across U.S. states and the years 1982-1997. State and federal alcohol taxes are used as instrumental variables for prices. RESULTS: Formal tests strongly confim the hypothesis of measurement error. Instrumental variable estimates of the price elasticity of demand range from -0.53 to -1.24. These estimates are substantially larger in absolute value than ordinary least squares estimates, which sometimes are not significantly different from zero or even positive. CONCLUSIONS: The ACCRA price data are substantially contaminated with measurement error, but using state and federal taxes as instrumental variables mitigates the problem.

Adolescent↗

Optimal timing of intervention in non-ST-segment elevation acute coronary syndromes: insights from the CRUSADE (Can Rapid risk stratification of Unstable angina patients Suppress ADverse outcomes with Early implementation of the ACC/AHA guidelines) Registry.

BACKGROUND: Recent studies indicate that a routine invasive approach for patients with unstable angina (UA) and non-ST-segment elevation myocardial infarction (NSTEMI) yields improved outcomes compared with a conservative approach, but the optimal timing of this approach remains open to debate. METHODS AND RESULTS: We used day of hospital presentation as an instrumental variable to study the impact of timing of cardiac catheterization and revascularization therapy on acute outcomes (death, reinfarction, stroke, cardiogenic shock, or congestive heart failure) among patients with UA and NSTEMI. Between January 2001 and September 2003, 56,352 patients with UA or NSTEMI were treated at 310 US hospitals participating in the CRUSADE national quality improvement initiative. Weekend patients were defined as those who presented to the hospital between 5 PM on Friday and 7 AM on Sunday. All other patients were classified as weekday. Weekday patients were similar to weekend patients in terms of demographics, clinical characteristics, and the use of medical therapies in the first 24 hours. Although overall rates of cardiac catheterization and revascularization were similar for the 2 groups, median time to catheterization was significantly longer for weekend than for weekday patients (46.3 versus 23.4 hours, P<0.0001). This delay was not associated with increased in-hospital adverse events, including death (weekend 4.4% versus weekday 4.1%, P=0.23), recurrent MI (2.9% versus 3.0%, P=0.36), or their combination (6.6% versus 6.6%, P=0.86). These findings were not affected by risk adjustment or use of alternative definitions of weekend versus weekday presentation. When weekend presentation was used as the basis for an instrumental variable analysis, we found that catheterization within the first 12 hours of presentation was associated with a nonsignificant trend toward reduced in-hospital mortality (absolute risk reduction 1.9%; 95% CI 6.7% lower to 2.9% higher; P=0.43) that decreased with longer treatment delays. CONCLUSIONS: Although weekend presentation is associated with a delay in invasive management among patients with UA and NSTEMI, in the context of contemporary medical therapy, this does not increase adverse events. Weekend presentation appears to fulfill accepted criteria as an instrumental variable for studying the optimal timing of invasive management for acute coronary syndrome patients. Using weekend status as an instrumental variable, we found no significant benefit to early catheterization, although we could not exclude an important risk reduction, particularly for catheterization within 12 hours of presentation.

Aged↗

Posthospitalization home health care use and changes in functional status in a Medicare population.

OBJECTIVE: The objective of this work was to estimate the effect of Medicare beneficiaries' use of home health care (HHC) for 6 months after hospital discharge on the change in functional status over a 1-year period beginning before hospitalization. DATA SOURCES AND STUDY SETTING: Data came from the Medicare Current Beneficiary Survey, which is a nationally representative sample of Medicare beneficiaries, in-person interview data, and Medicare claims for 1991 through 1994 for 2,127 nondisabled, community-dwelling, elderly Medicare beneficiaries who were hospitalized within 6 months of their annual in-person interviews. STUDY DESIGN: Econometric estimation with the instrumental variable method was used to correct for observational data bias, ie, the nonrandom allocation of discharged beneficiaries to the use of posthospitalization HHC. The analysis estimates a first-stage model of HHC use from which an instrumental variable estimate is constructed to estimate the effect on change in functional status. PRINCIPAL FINDINGS: The instrumental variable estimates suggest that HHC users experienced greater improvements in functional status than nonusers as measured by the change in a continuous scale based on the number and mix of activities of daily living and instrumental activities of daily living before and after hospitalization. The estimated improvement in functional status could be as large as 13% for a 10% increase in HHC use. In contrast, estimation with the observational data on HHC use implies that HHC users had poorer health outcomes. CONCLUSIONS: Adjusting for potential observational data bias is critical to obtaining estimates of the relationship between the use of posthospitalization HHC and the change in health before and after hospitalization. After adjustment, the results suggest that efforts to constrain Medicare's spending for HHC, as required by the Balanced Budget Act of 1997, may lead to poorer health outcomes for some beneficiaries.

Activities of Daily Living↗

Mortality and fertility: how large is the direct child replacement effect in China?

"The direct child replacement effect, that is the extent to which parents will have a child to replace one that died, was estime d by Olsen's method in China, using microdata from a sample survey of 4785 ever-married women in Hebei province taken in 1985. Olsen's method corrects for bias in the ordinary least squares estimate and uses mortality rates as an instrumental variable. Data for all age groups were pooled. Estimates of the direct replacement effect before and after correction for bias were 0.836 and 0.556, showing that over half of child deaths were replaced. The instrumental variable estimate produced a result of 0.614, similar to 0.613, computed by considering p1 to be random. A computation without instrumental variables yielded 0.774. The results showed that this method for calculating the direct replacement effect works well with these data because several of the alternative methods gave close estimates. There appears to be little family specific variation in child mortality rates, pointing out the effectiveness of Chinese primary health care. The direct replacement effect of about 0.6 is, however about 3 times that found by Olsen in Colombia and Malaysia, and close to the theoretical maximum. The reason for such a high value may be the small family size in China, where death of a child is more likely to provoke a response. Or it might suggest that severe government policy causes couples to attempt to have another child. Policy implications in this setting are that rather than make more contraceptives available, or improve infant survival, Chinese policymakers should make a small family size attractive, e.g., by improving education or pensions.

Asia↗

Technical variability of the RT3 accelerometer.

PURPOSE: To evaluate the technical performance of the RT3 triaxial accelerometer. METHODS: Twenty-three RT3 accelerometers were subjected to a specific vibration along each sensitive axis in isolation, using a motorized vibration table that produced frequencies of 2.1, 5.1, and 10.2 Hz, respectively. Data were analyzed for frequency and axis effects and inter- and intra-instrument variability. RESULTS: ANOVA showed a frequency by axis interaction (F2.1,36.8 = 19.9, P < 0.001). Post hoc tests revealed the Y axis count to be significantly higher than the X and Z axes counts at 5.1 and 10.2 Hz. There was no difference in counts between axes at 2.1 Hz. Interinstrument coefficients of variation (CV) decreased as frequency increased (21.9 to 26.7% at 2.1 Hz, 6.3 to 9.0% at 5.1 Hz, and 4.2 to 7.2% at 10.2 Hz). The intraclass correlation (ICC) between RT3s was 0.99, regardless of the axis. Intra-instrument CV also decreased as frequency increased (2.1 to 56.2%, 0.3 to 2.5%, and 0.2 to 2.9% at 2.1, 5.1, and 10.2 Hz, respectively. CONCLUSION: There were no differences in counts recorded on the X, Y, and Z axes at 2.1 Hz; however, the counts recorded along the Y axis were significantly higher than the counts at the X and Z axes at 5.1 and 10.2 Hz. Due to large coefficients of variation for both inter- and intra-instrument variability at 2.1 Hz, testing the inter- and intra-instrument variability of the accelerometers before use is recommended.

Acceleration↗

Technical reliability of the CSA activity monitor: The EarlyBird Study.

PURPOSE: To evaluate the technical performance of the CSA accelerometer-based activity monitor. METHODS: Twenty-three CSA monitors were subjected to intra- and inter-instrument variability tests by controlled trials using a motorized turntable. The CSA monitor measures change in acceleration, and precision was tested by producing sinusoidal variations in speed around two fixed baseline speeds (fast and medium). The angle of the monitor to the line of force along the radius of the turntable was varied using tilted blocks. Three sets of tests were carried out. 1. Intra-instrument variability: seven monitors were tested three times in each of the four quadrants. 2. All 23 monitors were used for inter-instrument tests. 3. The effects of tilt at 15 degrees, 30 degrees, and 45 degrees were carried out on six monitors. RESULTS: Intra-instrument coefficients of variation (CV) never exceeded 2% for fast or medium speed and achieved "between run" intra-class correlation coefficients (ICC) of 0.92 and 0.84 respectively. There were no significant differences between the monitors in terms of repeatability (fast: = 0.97, medium: = 0.77). Although there were significant differences between monitors in terms of mean score, inter-instrument variability did not exceed 5% at either speed. Inter-batch ICCs ranged from 0.87 to 0.98 for fast and from 0.71 to 0.99 for medium. The angle test results corresponded closely to those predicted theoretically, with a loss in mean score of only 6% when the monitor was tilted from 0 degrees to 15 degrees. CONCLUSION: The CSA monitor provides a precise tool for measuring changes in acceleration in laboratory settings. Technically, the device performs well, and is likely to prove a useful tool in the assessment of physical activity in children and adults.

Adult↗

Insurance and the utilization of medical services.

Most data sets indicate a positive correlation between having health insurance and utilizing health care services. Yet the direction of causality is not at all clear. If we observe a positive correlation between the utilization of health care services and insurance status, we do not know if this is because people who anticipate poor health buy more insurance (or take jobs with generous medical coverage), or because insurance lowers the cost of health care, increasing the quantity demanded. While a few attempts have been made to implement an instrumental variables (IV) strategy to deal with endogeneity, the instruments chosen have not been entirely convincing. In this paper we revisit the IV estimation of the reduced form relationships between insurance and health care utilization taking advantage of what we argue is a good instrument-the individual's self-employment status. Our main finding is that a positive and statistically significant effect of insurance continues to obtain even after instrumenting. Indeed, instrumental variables estimates of the impact of insurance on utilization of a variety of health care services are larger than their non-instrumented counterparts. The validity of this exercise depends on the extent to which self-employment status is a suitable instrument. To argue this case, we analyze panel data on transitions from wage-earning into self-employment and show that individuals who select into self-employment do not differ systematically from those who remain wage-earners with respect to either the utilization of health care or health status. While this finding does not prove that self-employment status is an appropriate instrument, it is encouraging that there appear to be no underlying differences that might lead to self-employment per se affecting health services utilization.

Adult↗

Multiple approaches to assessing the effects of delays for hip fracture patients in the United States and Canada.

OBJECTIVE: To examine the determinants of postsurgery length of stay (LOS) and inpatient mortality in the United States (California and Massachusetts) and Canada (Manitoba and Quebec). DATA SOURCES/STUDY SETTING: Patient discharge abstracts from the Agency for Health Care Policy and Research Nationwide Inpatient Sample and from provincial health ministries. STUDY DESIGN: Descriptive statistics by state or province, pooled competing risks hazards models (which control for censoring of LOS and inpatient mortality data), and instrumental variables (which control for confounding in observational data) were used to analyze the effect of wait time for hip fracture surgery on postsurgery outcomes. DATA EXTRACTIONS: Data were extracted for patients admitted to an acute care hospital with a primary diagnosis of hip fracture who received hip fracture surgery, were admitted from home or the emergency room, were age 45 or older, stayed in the hospital 365 days or less, and were not trauma patients. PRINCIPAL FINDINGS: The descriptive data indicate that wait times for surgery are longer in the two Canadian provinces than in the two U.S. states. Canadians also have longer postsurgery LOS and higher inpatient mortality. Yet the competing risks hazards model indicates that the effect of wait time on postsurgery LOS is small in magnitude. Instrumental variables analysis reveals that wait time for surgery is not a significant predictor of postsurgery length of stay. The hazards model reveals significant differences in mortality across regions. However, both the regressions and the instrumental variables indicate that these differences are not attributable to wait time for surgery. CONCLUSIONS: Statistical models that account for censoring and confounding yield conclusions that differ from those implied by descriptive statistics in administrative data. Longer wait time for hip fracture surgery does not explain the difference in postsurgery outcomes across countries.

Aged↗

Child outpatient mental health service use: why doesn't insurance matter?

BACKGROUND: Several recent studies of child outpatient mental health service use in the US have shown that having private insurance has no effect on the propensity to use services. Some studies also find that public coverage has no beneficial effect relative to no insurance. AIMS: This study explores several potential explanations, including inadequate measurement of mental health status, bandwagon effects, unobservable heterogeneity and public sector substitution for private services, for the lack of an effect of private insurance on service use. METHODS: We use secondary analysis of data from the three mainland US sites of NIMH's 1992 field trial of the Cooperative Agreement for Methodological Research for Multi-Site Surveys of Mental Disorders in Child and Adolescent Populations (MECA) Study. We examine whether or not a subject used any mental health service, school-based mental health services or outpatient mental health services, and the number of outpatient visits among users. We also examine use of general medical services as a check on our results. We conduct regression analysis; instrumental variables analysis, using instruments based on employment and parental history of mental health problems to identify insurance choice, and bivariate probit analysis to examine multiservice use. RESULTS: We find evidence that children with private health insurance have fewer observable (measured) mental health problems. They also appear to have a lower unobservable (latent) propensity to use mental health services than do children without coverage and those with Medicaid coverage. Unobserved differences in mental health status that relate to insurance choice are found to contribute to the absence of a positive effect for private insurance relative to no coverage in service use regressions. We find no evidence to suggest that differences in attitudes or differences in service availability in children's census tracts of residence explain the non-effect of insurance. Finally, we find that the lack of a difference is not a consequence of substitution of school-based for office-based services. School-based and office-based specialty mental health services are complements rather than substitutes. School-based services are used by the same children who use office-based services, even after controlling for mental health status. DISCUSSION: Our results are consistent with at least two explanations. First, limits on coverage under private insurance may discourage families who anticipate a need for child mental health services from purchasing such insurance. Second, publicly funded services may be readily available substitutes for private services, so that lack of insurance is not a barrier to adequate care. Despite the richness of data in the MECA dataset, cross-sectional data based on epidemiological surveys do not appear to be sufficient to fully understand the surprising result that insurance does not enable access to care. IMPLICATIONS FOR POLICY AND RESEARCH: Limits on coverage under private mental health insurance combined with a relatively extensive system of public mental health coverage have apparently generated a situation where there is no observed advantage to the marginal family of obtaining private mental health insurance coverage. Further research using longitudinal data is needed to better understand the nature of selection in the child mental health insurance market. Further research using better measures of the nature of treatment provided in different settings is needed to better understand how the private and public mental health systems operate.

Journal Article↗

Econometric approaches to epidemiologic data: relating endogeneity and unobserved heterogeneity to confounding.

The concepts of endogeneity and unobserved heterogeneity are well-known among econometricians. However, these issues are rarely addressed in epidemiologic studies. This paper explores these two concepts, their relationship to each other, and the implications for analysis in epidemiologic studies. An endogenous variable is defined as a predictor variable which is partly determined by factors within the model itself, while unobserved heterogeneity is conceptualized as a vector of missing variables acting through the error term. Under certain assumptions, the simultaneous existence of an endogenous variable and unobserved heterogeneity is shown to act in a manner analogous to confounding. Specifically, this occurs due to an association between the error term in the equation and the endogenous predictor variable. The accepted econometric solution to this problem is to replace the endogenous variable with an 'instrumental variable' which is not correlated with the error term and thus not susceptible to confounding. The validity of these concepts and of the proposed solution are discussed.

Confounding Factors, Epidemiologic↗

Income disparities in the quality of life of cancer survivors.

BACKGROUND: Studies of cancer survivors usually report positive correlations between income and health-related quality of life (QoL). These correlations cannot necessarily be interpreted as income disparities because earnings and income are affected by health, as well as the reverse. OBJECTIVES: The goal of this study was to quantify income disparities in QoL among cancer survivors by using instrumental variables (IV) to assess and, if necessary, correct for reverse causality. METHODS: We constructed an instrumental variable for income from home ownership, sources of unearned income, marital status at diagnosis, and spousal characteristics. Then, we examined income's effect on QoL in regressions controlling for other clinical and demographic predictors of QoL. The data were from interviews in 2002 with a cohort of cancer survivors who were 25 to 62 years of age when diagnosed during 1997 to 1999. MEASURES: The Functional Assessment of Cancer Therapy-General (FACT-G) and the SF-12 measured QoL in multiple domains. Questions adapted from the Health and Retirement Study ascertained the ratio of annual family income to the poverty threshold in 2001. RESULTS: Endogeneity tests were sensitive to assumptions of linearity for the income-QoL relationship and the choice of QoL measure. Consistently estimated income disparities were significant in all QoL models. The income elasticity of QoL ranged from 2% to 10%. CONCLUSIONS: There are income-related disparities in the QoL of cancer survivors that cannot be explained away by the effect of health on earnings. High-income patients are not only more likely to survive cancer, but they enjoy better QoL as survivors.

Adult↗

Risk of death in elderly users of conventional vs. atypical antipsychotic medications.

BACKGROUND: Recently, the Food and Drug Administration (FDA) issued an advisory stating that atypical antipsychotic medications increase mortality among elderly patients. However, the advisory did not apply to conventional antipsychotic medications; the risk of death with these older agents is not known. METHODS: We conducted a retrospective cohort study involving 22,890 patients 65 years of age or older who had drug insurance benefits in Pennsylvania and who began receiving a conventional or atypical antipsychotic medication between 1994 and 2003. Analyses of mortality rates and Cox proportional-hazards models were used to compare the risk of death within 180 days, less than 40 days, 40 to 79 days, and 80 to 180 days after the initiation of therapy with an antipsychotic medication. We controlled for potential confounding variables with the use of traditional multivariate Cox models, propensity-score adjustments, and an instrumental-variable analysis. RESULTS: Conventional antipsychotic medications were associated with a significantly higher adjusted risk of death than were atypical antipsychotic medications at all intervals studied (< or =180 days: relative risk, 1.37; 95 percent confidence interval, 1.27 to 1.49; <40 days: relative risk, 1.56; 95 percent confidence interval, 1.37 to 1.78; 40 to 79 days: relative risk, 1.37; 95 percent confidence interval, 1.19 to 1.59; and 80 to 180 days: relative risk, 1.27; 95 percent confidence interval, 1.14 to 1.41) and in all subgroups defined according to the presence or absence of dementia or nursing home residency. The greatest increases in risk occurred soon after therapy was initiated and with higher dosages of conventional antipsychotic medications. Increased risks associated with conventional as compared with atypical antipsychotic medications persisted in confirmatory analyses performed with the use of propensity-score adjustment and instrumental-variable estimation. CONCLUSIONS: If confirmed, these results suggest that conventional antipsychotic medications are at least as likely as atypical agents to increase the risk of death among elderly persons and that conventional drugs should not be used to replace atypical agents discontinued in response to the FDA warning.

Aged↗

Dietary intake assessments in epidemiology: can we know what we are measuring?

PURPOSE: We discuss fundamental assumptions required for the validation of dietary questionnaire assessments, using latent variable models. METHODS: We discuss some methodological aspects of latent variable modelling in terms of the triad method, for comparisons between questionnaire assessments, food consumption records and/or biomarkers. In particular, we address the recent proposal (Frazer et al) that biases due to correlated random errors between different measurement types could be overcome by using two biomarkers as instrumental variables, as recently proposed by. RESULTS: The instrumental variable approach proposed by Frazer et al, but also other validation models proposed so far, require the assumption that questionnaire measurements are specific for a defined type of food or nutrient intake (latent variable of interest) - that is, conditionally on the true intake levels of this food or nutrient the questionnaire measurements should have no association with intakes of any other dietary component. CONCLUSION: More methodological research is needed on the design of multivariate validation studies that might allow the examination of measurement specificity in practice.

Data Collection↗

In-vitro biomechanical study of a dorso-lumbo-sacral posterior supple instrumentation with variable section.

This study is designed to analyse the behavior, in the sagittal plane, of a complete human dorso-lumbar rachis, made rigid by the posterior instrumentation used for the treatment of scoliosis, on subjects suffering from DMD (Duchenne Muscular Dystrophy). The object of this analysis is to demonstrate the reliability of early surgery made possible by new instrumentation. Close review of the literature shows that the currently used Harrington or Luque instrumentations lead to mechanical complications, especially rod breaking, at the thoraco-lumbar junction. 8 specimens were non-destructively tested in-vitro. Compression and flexion were applied. For each test, rachis movements with and then without instrumentation, and also rod restraints were noted. The results show a linear stiffness multiplied by 8.3 in flexion and 11.6 in extension. The maximum restraint recorded for physiological displacements is 77 MPa. This remains largely under the fatigue-breaking limit of the metal used (stainless steel hammer-hardened 316 L, Young's modulus = 200,000 MPa, Poisson's ratio = 0.21, endurance limit = 350 MPa at 5 x 10(6) cycles). The results of this study encourage us to continue and develop early surgery in children affected by myopathy, with fixation of the complete rachis, including a lumbo-sacral arthrodesis and a supple dorsal part of the mounting, in the sagittal plane.

Aged↗

Immunosuppressant use may be a potential mediator in the progression of systemic lupus erythematosus to osteomyelitis: A bidirectional Mendelian randomization study.

The prevalence of osteomyelitis (OM) is elevated in patients with systemic lupus erythematosus (SLE), but the causal direction and proportion of immunosuppressant (IS) use in this relationship is unclear. Therefore, this study used a bidirectional Mendelian randomization (MR) study to investigate the causal relationship between SLE and OM and to quantify the role of IS use as a potential mediator. Genome-wide association study summary-level data were used to obtain genetic instrumental variables for SLE (5201 cases and 9066 controls), OM (1881 cases and 391,037 controls), and IS (3954 cases and 268,648 controls) genetic instrumental variables with no overlap between their participant populations. Causal and total effects of SLE and OM were analyzed using bidirectional MR. Subsequent "2-step" MR was used to assess the direct effect between the 2 and the indirect effect of IS. Inverse variance weighting was used as the primary method of MR, while a series of sensitivity analyses were performed to assess the reliability of the results. Forward MR of inverse variance weighting results demonstrated a positive causal association between SLE and OM (P&#x2005;=&#x2005;.003, odds ratio [OR]&#x2005;=&#x2005;1.062, 95% confidence interval [Cl]-OR: 1.019-1.107). The reverse MR results indicated no causal effect of OM on SLE was found (P&#x2005;=&#x2005;.503, OR&#x2005;=&#x2005;0.914, 95% Cl-OR: 0.703-1.188). The direct effect of SLE acting on OM in our study was found to be 19.36% by 2-step analysis, and the indirect effect of OM through IS was found to be 68.11% (proportion mediated: 68.11%; 95% CI&#x2005;=&#x2005;0.2277331-1.134507). There was no heterogeneity in all MR analyses of causality, except for the MR analysis of SLE causally related to IS. Sensitivity analysis found no evidence of horizontal pleiotropy. The present study found an increased relative risk of OM in SLE. Mediation analysis suggested a potential substantial mediating role for IS; however, this estimate was highly imprecise and requires further validation. In clinical practice, clinicians should remain aware of the potential for IS therapy to influence infection risk, including OM, in SLE patients.

Humans↗