Linear Spline Regression Models Research Articles

Opioid-limiting legislation and prescribing habits of otolaryngologists among Medicare beneficiaries.

To identify changes in otolaryngologists' opioid prescribing trends for Medicare beneficiaries associated with the enactment of state laws that limit the duration of prescriptions to 3-7 days in the years 2016 and 2017 in the United States. Through the Centers for Medicare and Medicaid Services (CMS) database, we retrieved data on Medicare enrollment and on the total days prescribed and total number of beneficiaries for the drugs codeine/acetaminophen, hydrocodone/acetaminophen, oxycodone HCl, oxycodone/acetaminophen, and tramadol HCl, by each otolaryngologist prescriber in 13 states from January 2013 to December 2019. We modeled trends using linear spline regression models that controlled for Medicare beneficiaries' state-level socio-demographic characteristics' fixed effects. Across the 13 states, the number of days of all five opioids prescribed per beneficiary declined by 8.35 (SD = 12.61). The most commonly prescribed opioid type by otolaryngologists during the 5-year study period was tramadol HCl (28.72 days/beneficiary) followed by oxycodone HCl (19.99 days/beneficiary). All opioids had declines in prescription days over this time window and higher rates of decline in the years following law passage. Four states experienced statistically significant declines in the prescriptions of all opioids after the year of legislation passage (p < .05). Some states that had the greatest inclines in opioid prescriptions in the years prior to law enactment also experienced the greatest reductions in the time after legislation enactment. Opioid prescribing practices of otolaryngologists may have been affected by opioid prescription duration limiting laws passed in 13 states in 2016 and 2017. Level 4.

The role of family, school and neighbourhood in explaining inequalities in physical activity trajectories between age 9 and 18

Differentials in physical activity (PA) between social and economic groups has been shown to contribute significantly to social gradients in health and life expectancy, yet relatively little is known about why differentials in PA emerge. This paper uses longitudinal data on a nationally representative sample of 6,216 young people aged between 9 and 18, from Ireland, to measure the role of family, school and neighbourhood level factors in accounting for differentials in PA trajectories between groups of young people, defined by level of maternal education, whilst adjusting for the individual characteristics of the young person (sex, age, personality, body mass index and health-status). Levels of PA fall significantly across the sample between 9 and 18, and the decline in PA is larger for the children of lower educated mothers. We find a clear gradient in PA at each age by maternal education for both males and females. Descriptive analyses found social gradients in the majority of our risk factors. Using multi-level, linear spline regression models to decompose differentials between groups, we find that family-level mechanisms account for the biggest proportion of the differential in PA for both males (50.8%) and females (35.1%). Differences in income across maternal education categories accounted for 24.1% of the differential for males and 14.7% among females, making it the second most effective mechanism in explaining the social patterning of PA. Neighbourhood-level processes resulted in a modest reduction in the same differential, while school level processes had the effect of equalising differences in PA across maternal education groups.

Relationships Between 25-Hydroxyvitamin D, Parathyroid Hormone, and Bone Mass in 4-Year-Old Children in Dhaka, Bangladesh

ObjectivesElevated serum parathyroid hormone (PTH) concentration was incidentally observed in a high proportion of children in a study in Dhaka, Bangladesh. We explored potential correlates of elevated PTH by estimating the association of PTH with 25-hydroxyvitamin D (25(OH)D) and associations of 25(OH)D and PTH with bone outcomes.MethodsData were obtained from the BONe and mUScle health in Kids study (BONUSKids; NCT03537443). Total-body less head (TBLH) bone mineral content (BMC) and areal bone mineral density (aBMD) were measured by dual-energy X-ray absorptiometry (DXA). Serum PTH and 25(OH)D were analyzed by chemiluminescent immunoassay and liquid chromatography-tandem mass spectrometry, respectively. BONUSKids participants (n = 642) with DXA, PTH and 25(OH)D data at 4 years were included. Associations between 25(OH)D, PTH and bone outcomes were estimated using unadjusted linear and two-phase linear spline regression models. Model fit was compared using AIC.ResultsAmong the 534 children who met inclusion criteria, 43% were vitamin D deficient (< 30nmol/L) and 30% had PTH > 6.9pmol/L. A non-linear inverse relationship was observed between 25(OH)D and PTH. Model fit was optimized with an inflection point at 25nmol/L, above which the association attenuated (< 25nmol/L: −0.16pmol/L per 1nmol/L change in 25(OH)D [95%CI −0.23, −0.10]; ≥ 25nmol/L: –0.02pmol/L [95% CI −0.04, −0.008]. 25(OH)D was positively linearly associated with TBLH BMC (0.39g per 1nmol/L change in 25(OH)D [95%CI 0.10: 0.69]) and aBMD (0.0004g/cm2 per 1nmol/L change in 25(OH)D [95% CI 0.0002, 0.0006]). There was no significant association between PTH and TBLH BMC. The non-linear association between PTH and TBLH aBMD was negative at PTH > 4pmol/L (< 4pmol/L: 0.002g/cm2 per 1pmol/L change in PTH [95% CI –0.006, 0.01], ≥ 4pmol/L: −0.002g/cm2 [95% CI −0.0038, −0.0002]).ConclusionsThe non-linear inverse association of PTH with 25(OH)D supports the hypothesis that vitamin D deficiency contributed to elevated PTH in this population. Although 25(OH)D was associated with bone outcomes, the magnitude of the association was similar at 25(OH)D concentrations below and above 25nmol/L. PTH was inconsistently associated with bone outcomes, suggesting single measurements of PTH may not be a useful marker of bone health in this setting.Funding SourcesCanadian Institutes of Health Research.

Walking while Talking in Older Adults with Chronic Kidney Disease.

Walking while talking is a dual cognitive-motor task that predicts frailty, falls, and cognitive decline in the general elderly population. Adults with CKD have gait abnormalities during usual walking. It is unknown whether they have greater gait abnormalities and cognitive-motor interference during walking while talking. Community-dwelling, nondisabled adults (n=330) ≥65 years of age underwent quantitative gait analysis, including walking while talking. Differences in walking-while-talking performance by CKD status were evaluated, and relative changes between walking-while-talking and walking alone performance were computed to quantify cognitive-motor interference (dual-task cost). Associations were tested using multivariable linear spline regression models, and independent gait domains were derived using factor analysis. CKD was defined as an eGFR<60 ml/min per 1.73 m2. CKD was present in 134 (41%) participants. Participants with CKD had slower gait speed along with various gait cycle abnormalities during walking while talking: among those with CKD, every 10-ml/min per 1.73 m2 lower eGFR was associated with 3.3-cm/s (95% confidence interval, 0.4 to 6.1) slower gait speed, 1.8-cm (95% confidence interval, 0.6 to 3.0) shorter step length, 1.1% (95% confidence interval, 0.6 to 1.7) less time in the swing phase, and 1.4% (95% confidence interval, 0.5 to 2.3) greater time in double support after multivariable adjustment. When comparing walking while talking with walking alone, every 10-ml/min per 1.73 m2 lower eGFR was associated with 1.8% (95% confidence interval, 0.5 to 3.2) greater decrease in time in the swing phase and 0.9% (95% confidence interval, 0.2 to 1.5) greater increase in time in the stance phase. Factor analysis identified three walking-while-talking domains and three dual-task cost domains: eGFR was associated specifically with the rhythm domain for both walking-while-talking and dual-task cost. Every 10-ml/min per 1.73 m2 lower eGFR was associated with a poorer performance of 0.2 SD (95% confidence interval, 0.1 to 0.3) for walking while talking and 0.2 SD (95% confidence interval, 0.03 to 0.3) for dual-task cost. During walking while talking, CKD is associated with gait abnormalities, possibly due to increased cognitive-motor interference.

Trends in the Price per Median and Mean Life-Year Gained Among Newly Approved Cancer Therapies 1995 to 2017

BackgroundThe prices of newly approved cancer drugs have risen over the past decades. A key policy question is whether the clinical gains offered by these drugs in treating specific cancer indications justify the price increases. ObjectivesTo evaluate the price per median and mean life year gained among newly approved cancer therapies from 1995 to 2017. MethodsWe collected data on the price (in 2017 USD) per life-year gained among cancer drug-indication pairs approved by the US Food and Drug Administration (FDA) between 1995 and 2017. We modeled trends using fractional polynomial and linear spline regression models that controlled for route of administration and cancer type fixed effects. ResultsWe found that between 1995 and 2012, price increases outstripped median survival gains, a finding consistent with previous literature. Nevertheless, price per mean life-year gained increased at a considerably slower rate, suggesting that new drugs have been more effective in achieving longer-term survival. Between 2013 and 2017, price increases reflected equally large gains in median and mean survival, resulting in a flat profile for benefit-adjusted launch prices in recent years. ConclusionsAlthough drug costs have been rising more rapidly than median survival gains, they have been rising at about the same rate as mean survival gains. This suggests that when accounting for longer-term survival gains, the benefits of new drugs are roughly keeping pace with their costs, despite rapid cost growth.

Trends in Hospital Readmission of Medicare-Covered Patients With Heart Failure

BackgroundThe Medicare Hospital Readmissions Reduction Program has led to fewer readmissions following hospitalizations with a principal diagnosis of heart failure (HF). Patients with HF are frequently hospitalized for other causes. ObjectivesThis study sought to compare trends in Medicare risk-adjusted, 30-day readmissions following principal HF hospitalizations and other hospitalizations with HF. MethodsThis was a retrospective study of 12,973,853 Medicare hospitalizations with a principal or secondary diagnosis of HF between January 2008 and June 2015. Hospitalizations were categorized as follows: principal HF hospitalizations; principal acute myocardial infarction or pneumonia hospitalizations with secondary HF; and other hospitalizations with secondary HF. The study examined trends in risk-adjusted, 30-day, all-cause readmission rates for each cohort and trends in differences in readmission rates among cohorts by using linear spline regression models. ResultsBefore passage of the Affordable Care Act in March 2010, risk-adjusted, 30-day readmission rates were stable for all 3 cohorts, with mean monthly rates of 26.1%, 24.9%, and 24.4%, respectively. Risk-adjusted readmission rates started declining after passage of the Affordable Care Act by 1.09% (95% confidence interval [CI]: 0.51% to 1.68%), 1.24% (95% CI: 0.92% to 1.57%), and 1.05% (95% CI: 0.52% to 1.58%) per year, respectively, until implementation of the Hospital Readmissions Reduction Program in October 2012 and then stabilized for all 3 cohorts. ConclusionsPatients with HF are often hospitalized for other causes, and these hospitalizations have high readmission rates. Policy changes led to decreases in readmission rates for both principal and secondary HF hospitalizations. Readmission rates in both groups remain high, suggesting that initiatives targeting all hospitalized patients with HF continue to be warranted.

The Transition to Data-Driven Quality Metrics: Determining the Optimal Surveillance Period for Complications After Surgery

BackgroundThirty-day complications frequently serve in the surgical literature as a quality indicator. This metric is not meant to capture the full array of complication resulting from surgical intervention. However, this period is largely based on convention, with little evidence to support it. This study sought to determine the optimal surveillance period for postsurgical complications, defined as the shortest period that also encompassed the highest proportion of postsurgical adverse events. MethodsTRICARE data (2006-2014) were queried for adult (18-64 y) patients who underwent one of 11 surgical procedures. Patients were assessed for complications up to 90 d after surgery. Kaplan–Meier curves, linear spline regression models at each incremental postsurgical day, and adjusted R-squared values were used to identify critical time point cutoffs for the surveillance of complications. Optimal length of surveillance was defined as the postsurgical day on which the model demonstrated the highest R-squared value. A supplemental analysis considered these measures for orthopedic and general surgical procedures. ResultsOne lakh ninety-eight patients met the inclusion criteria. A total of 21.8% patients experienced at least one complication during the follow-up period, with 59% occurring within the first 15 d. Kaplan–Meier curves for complications showed a demonstrable inflection before 20 d and 14-15 d possessed the highest R-squared values. ConclusionsIn this analysis, the optimal surveillance period for postsurgical complications was 15 d. While the conventional 30-d period may still be appropriate for a variety of reasons, the shorter interval identified here may represent a superior quality measure specific to surgical practice.

Children's Health Insurance and Access to Care During and After the CHIP Expansion Period

We used national data from the Medical Expenditure Panel Survey and multivariate linear spline regression models to compare trends in children's health insurance coverage and access to care by income and race/ethnicity during (1998-2002) and after (2002-2006) major expansions of state insurance programs. During expansions, coverage and access for children in low-income and middle-income families improved, but these gains ceased thereafter for middle-income children, most of whom remained ineligible for public insurance. Racial and ethnic differences narrowed from 1998-2002, but persisted-and in at least one case tended to widen-from 2002-2006. Non-White children in families with incomes above most states' eligibility thresholds experienced significant declines in coverage and access to care after 2002. Gains in children's coverage and access to care during CHIP expansions have since stagnated or even reversed for some groups. Recent legislation to expand coverage for uninsured children (the PPACA of 2010) may redress these adverse changes in trends.

The Impact of Obesity on the Left Ventricle: The Multi-Ethnic Study of Atherosclerosis (MESA)

The purpose of this study was to evaluate the relationship of left ventricular (LV) remodeling assessed by cardiac magnetic resonance to various measures of obesity in a large population-based study. Obesity is a well-known risk factor for cardiovascular disease, yet its relationship with LV size and function is poorly understood. A total of 5,098 participants (age 45 to 84 years; 48% men) in the Multi-Ethnic Study of Atherosclerosis who were free of clinically apparent cardiovascular disease underwent cardiac magnetic resonance to assess LV size and function as well as measures of obesity, including body mass index, waist-to-hip ratio and waist circumference, and cardiovascular risk factors. Fat mass (FM) was estimated based on height-weight models derived from bioelectrical impedance studies. The associations of obesity measures with LV size and function were evaluated using linear spline regression models for body mass index and multivariable regression models for other measures of obesity; they were displayed graphically using generalized additive models. LV mass and end-diastolic volume were positively associated with measures of obesity in both sexes after adjustment for risk factors (e.g., 5.7-g and 6.9-g increase in LV mass per 10-kg increase in FM in women and men, respectively [p < 0.001]). LV mass-to-volume ratio was positively associated with increased body mass index, waist-to-hip ratio, waist circumference, and estimated FM (e.g., 0.02-g/ml and 0.06-g/ml increase in mass-to-volume ratio per 10-kg increase in FM in women and men, respectively [p < 0.001]). The increased mass-to-volume ratio was due to a greater increase in LV mass relative to LV end-diastolic volume. All associations were stronger for men than for women. Ejection fraction showed no significant association with measures of obesity. Obesity was associated with concentric LV remodeling without change in ejection fraction in a large, multiethnic cohort study.

Evaluation and Modeling of Rate-Reducing Resistance of Soybean Seedlings toPhytophthora sojae

Lesion length and rate of lesion expansion on taproots of aeroponically grown soybeans infected with Phyrophrhora sojae provided an accurate assessment of rate-reducing resistance. Four days after inoculation with race 3 of P. sojae (1,000 zoospores/plant), mean lesion lengths for the cultivars Corsoy, Sloan, Cumberland, Williams, Asgrow 3127, Agripro 26, and Asgrow 2575 were 8.7, 8.6, 7.0, 7.0, 7.7, 5,2, and 4.0 cm, respectively (LSD 0.05 =0.84). Linear spline regression models consisting of two intersecting straight lines with slopes B 1 and B 2 were used to describe lesion expansion over a 14-day period for each cultivar []