Ordinary Least-squares Regression Analysis Research Articles

Anterior capsule contraction and flare intensity in the early stages after cataract surgery in eyes with diabetic retinopathy

To evaluate the changes and relationship in the area of the anterior capsule opening (ACO) and anterior inflammation during the early stages after cataract surgery in diabetic patients with or without diabetic retinopathy (DR). Department of Ophthalmology, University of Fukui, Fukui, Japan. Case-control study. This study comprised diabetic patients without DR (non-DR group), diabetic patients with nonproliferative DR (DR group), and patients without diabetes mellitus (DM) (non-DM group) who had cataract surgery. The ACO area and aqueous flare intensity were measured using the EAS-1000 device and a laser flare-cell meter, respectively, 1 day, 1 week, and 1 and 3 months after surgery. The percentage of anterior capsule contraction (ACC) was significantly higher in the DR group than in the non-DR and non-DM groups 1 week and 1 and 3 months postoperatively (P<.01, Turkey-Kramer test). The aqueous flare intensity was significantly greater in the DR group than in the non-DR and non-DM groups 1 day, 1 week, and 1 and 3 months postoperatively (P<.01). Ordinary least-squares regression analysis showed a significant positive correlation between aqueous flare intensity at 1 week and ACC 3 months after surgery in the non-DR group (P=.0178, R(2) = 0.173) and the DR group (P=.0018, R(2) = 0.308). Greater anterior flare levels 1 week after cataract surgery contributed to the extensive postoperative contraction of the ACO in diabetic patients, particularly those with DR.

Label-free detection of peripheral nerve tissues against adjacent tissues by spontaneous Raman microspectroscopy

Detection of peripheral nerve tissues during surgery is required to avoid neural disturbance following surgery as an aspect of realizing better functional outcome. We provide a proof-of-principle demonstration of a label-free detection technique of peripheral nerve tissues, including myelinated and unmyelinated nerves, against adjacent tissues that employ spontaneous Raman microspectroscopy. To investigate the Raman spectral features of peripheral nerves in detail, we used unfixed sectioned samples. Raman spectra of myelinated nerve, unmyelinated nerve, fibrous connective tissue, skeletal muscle, tunica media of blood vessel, and adipose tissue of Wistar rats were analyzed, and Raman images of the tissue distribution were constructed using the map of the ordinary least squares regression (OLSR) estimates. We found that nerve tissues exhibited a specific Raman spectrum arising from axon or myelin sheath, and that the nerve tissues can be selectively detected against the other tissues. Moreover, myelinated and unmyelinated nerves can be distinguished by the intensity differences of 2,855 cm⁻¹, and 2,945 cm⁻¹, which are mainly derived from lipid and protein contents of nerve fibers. We applied this method to unfixed section samples of human periprostatic tissues excised from prostatic cancer patients. Myelinated nerves, unmyelinated nerves, fibrous connective tissues, and adipose tissues of the periprostatic tissues were separately detected by OLSR analysis. These results suggest the potential of the Raman spectroscopic observation for noninvasive and label-free nerve detection, and we expect this method could be a key technique for nerve-sparing surgery.

Psychological Correlates of Violent and Non‐violent Hong Kong Juvenile Probationers

There is little known about Hong Kong juvenile offenders on probation. The purpose of this study was to compare Hong Kong juvenile violent with non-violent probationers on static demographic and psychological variables. The study comprised 109 male juvenile probationers aged 14-20 years (M = 16.97, SD = 1.44) in community transitional housing; 34 were adjudicated for violent offenses, while 75 were non-violent. The Rosenberg Self-Esteem Scale (RSES), Satisfaction with Life Scale (SWLS), Social Bonding Scale-Theft (SBS-T), Social Bonding Scale-Violent Crime (SBS-VC), Positive and Negative Affect Scales (PANAS), Impulsiveness Scale-Short Form (IS-SF) and CRIME-PICS II were administered to measure self-esteem, life satisfaction, social bond, positive and negative affect, impulsivity, pro-offending attitudes, and self-perceived life problems. Data on onset age of delinquent behavior, age of first adjudication, number of prior adjudications, and frequency of self-reported delinquency in the past year were also collected. t-tests were consistent with significant differences for violent offenders including higher self-esteem (p < 0.05). Non-violent offenders self-reported significantly more theft (p < 0.05) with a tendency to deny victim hurt more often (p < 0.01); 76.5% of violent offenders self-reported both violent and non-violent crime, while 58.7% of non-violent offenders reported only non-violent crime. For violent and non-violent offenders, the onset of delinquency was inversely related to the frequency of self-reported delinquency. Using ordinary least-squares (OLS) regression analyses, self-anticipated violent reoffending risk was predicted by age of onset, frequency of self-reported delinquency, social bond (inversely), and impulsivity, while non-violent reoffending risk was predicted by the number of prior convictions and self-reported delinquency. Only two psychological correlates, social bond and impulsivity, were related to violent delinquency; interventions are suggested.

Health Care Service Needs and Correlates of Quality of Life: A Case Study of Elderly Chinese Immigrants in Canada

This study explored the health care service needs and the major correlates of quality of life among 127 community-dwelling elderly Chinese immigrants in a western Canadian city. Participants were interviewed in their homes by trained, bilingual interviewers employing a structured questionnaire that covered a wide range of topics including health care service needs, living arrangements, health status, social network, life satisfaction, and socio-demographic information. Results demonstrated that ethnic nursing homes, senior centres that provide programs and services, and homemaker services were respondents’ major service needs. Multiple ordinary least-squares regression analysis revealed that respondents who emigrated from Mainland China and those who exhibited greater psychological well-being, reported being physically more mobile, perceived fewer service needs, and expressed satisfaction with the quality of their neighbourhood demonstrated higher levels of life satisfaction.

Work-Related Burnout, Job Satisfaction, Intent to Leave, and Nurse-Assessed Quality of Care Among Travel Nurses

This research study examines work-related burnout, job satisfaction, nurse-assessed quality of care, and intent to leave in travel nurses, a population that has not been studied previously. Travel nurses are frequently used to supplement nursing staff in acute care hospitals, especially in times of shortage--understanding their satisfaction with the job may further illuminate the problem of nurse job dissatisfaction in general. Ordinary least-squares regression analyses were used to examine the influence of nurse and workplace characteristics on work-related burnout, job satisfaction, intent to leave, and perceived quality of care. Quality of care and job satisfaction were significantly influenced by whether a hospital held Magnet designation. As the number of patients cared for increases, there was a significant increase in work-related burnout. Work-related burnout was also significantly lower for nurses working in California. The results of this study suggest that different workplace characteristics influence the perceptions of quality of care provided at a hospital facility and the degree to which a nurse is either burned out or satisfied with his/her job.

A Simple Approach to the Estimation of Incidence Rate Difference

The incidence rate difference (IRD) is a parameter of interest in many medical studies. For example, in vaccine studies, it is interpreted as the vaccine-attributable reduction in disease incidence. This is an important parameter, because it shows the public health impact of an intervention. The IRD is difficult to estimate for various reasons, especially when there are quantitative covariates or the duration of follow-up is variable. In this paper, the authors propose an approach based on weighted least-squares regression for estimating the IRD. It is very easy to implement because it boils down to performing ordinary least-squares regression analysis of transformed variables. Furthermore, if the outcome events are repeatable, the authors propose that data on all events be analyzed instead of first events only. Four versions of the Huber-White robust standard error are considered for statistical inference. Simulation studies are used to examine the performance of the proposed method. In a variety of scenarios simulated, the method provides an unbiased estimate for the IRD, and the empirical coverage proportion of the 95% confidence interval is very close to the nominal level. The method is illustrated with data from a vaccine trial carried out in the Gambia in 2001-2004.

Growing old in Canada: physical and psychological well-being among elderly Chinese immigrants

Objective. Immigrants are a vital component of the current and future ethnic aging population in Canada. This study was undertaken to explore the health status of elderly Chinese immigrants in a western Canadian city and to identify the major determinants of their physical and psychological well-being. Method. Using a 50% random sample of elderly Chinese residing in three residential complexes occupied exclusively by individuals of ethnic Chinese origin located in downtown Calgary, a total of 147 Chinese seniors were interviewed in their homes by trained, bilingual interviewers using a structured questionnaire that covered a wide range of topics including health status, social network, living arrangements, use of health-related services, and socio-demographic information. Data analysis. Descriptive and inferential analyses were conducted using the Statistical Package for the Social Sciences. A principal component factor analysis using varimax rotation was performed to explore the underlying factorial structure of the seven items measuring well-being. The internal consistency of all scales used was assessed by Cronbach's alpha reliability test. Two multiple ordinary least-squares (OLS) regression models were constructed to identify the major determinants of respondents' physical and psychological well-being. Results. The findings revealed that a majority of the participants described their physical health as good or very good. Results of multiple OLS regression analysis demonstrated that education, country of origin, use of medications, physical mobility, and perceived financial needs were significantly associated with physical well-being, whereas sex, marital status, length of residence, education, and physical mobility were significantly related to psychological well-being. Conclusion. Healthcare professionals, service providers, and policy-makers need to understand the significant impact of the various socio-demographic and background variables that contribute to the well-being of community-dwelling Chinese elderly immigrants. The provision of culturally sensitive and linguistically appropriate healthcare, social, and medical services is needed for the growing older Chinese population. Future studies should compare the health status of foreign-born Chinese seniors with those who were native-born, as well those co-residing with adult children.

S63-01 HPA-axis function and depression in adolescence: are they related to prenatal early life stress?

Early-life exposure to adverse environmental cues during critical windows of time in the prenatal and/or early postnatal life period could predispose the individual for somatic andmental diseases. This especially holds for stress-related disorders such as depression in which HPA-axis dysregulation plays a pathophysiological role. This is in line with the ‘fetal (or developmental) programming-hypothesis’ which has been tested in numerous preclinical experimental. We tested this hypothesis in humans in a prospective longitudinal study in which maternal emotional state was measured during each pregnancy trimester and after pregnancy. When the offspring was 14-15 years old, HPA-axis function was measured through establishing a saliva day-time cortisol profile. Severity of depressive symptoms was measured with the Children's Depression Inventory. Repeated measurements regression analysis and ordinary least-squares regression analyses indicated that maternal anxiety at 12-22 weeks of pregnancy was in female and male offspring associated with a diurnal cortisol profile that was attenuated due to elevated cortisol secretion in the evening. Moreover, in female adolescents this flattened cortisol curve was associated with depressive symptoms. Our results indicate that maternal anxiety during pregnancy enhances neurobiological vulnerability to depressive symptoms, possibly by altering (or ‘programming") foetal physiology. If our results can be replicated in future research they may lead to a re-orientation of the target of primary prevention and treatment of depressive symptoms. Preliminary results of a study on the association between prenatal exposure to maternal anxiety and cortisol stress responsivity during inoculation in the four month old will be presented.

Improving Medication Management of Depression in Health Plans

Improving Medication Management of Depression in Health Plans

Psychological well-being and scholastic achievement among university students in a Canadian Prairie City

This article reports the findings from a questionnaire survey of university students’ scholastic achievement and psychological well-being in a Canadian prairie city. Multiple ordinary least-squares regression analyses revealed that sex, educational aspirations, hours spent on studying, father’s education, physical health, financial stress, and stress due to balancing work, school, and social life were found to be significantly associated with academic performance. More specifically, female students and those who reported higher educational aspirations, indicated better physical health, experienced less financial stress or stress due to finance or to balancing work, school, and social life, spent more time on studying, and those whose father had a higher level of education were found to perform better academically. On the other hand, income, physical health, relationship with significant other, relationship with family, relationships with friends, self image, and academic stress were found to be significantly related to psychological well-being. Put succinctly, respondents who had a higher family income, reported better physical health, expressed a higher degree of satisfaction with their relationships with family, friends, and significant other, indicated a more positive self-image, and experienced less academic stress were found to exhibit a significantly higher level of psychological well-being.

Association between factors related to the time of wearing complete dentures and oral health-related quality of life in patients who maintained a recall

To investigate the association between factors related to the time of wearing complete dentures (CDs) and oral health-related quality of life (OHRQoL) in edentulous patients who maintained a recall.OHRQoL was measured using the German version of the Oral Health Impact Profile (OHIP-G) in a convenience sample of 50 edentulous prosthodontic patients (mean age+/- SD: 72.5 +/-9.4; age range: 52 to 91 years, 66% women) maintaining a recall 2 to 51 months after CD treatment. The outcome of the study was the sum of OHIP-G item responses (OHIP-G49; range, 0 to 196) that characterized OHRQoL. Exposure variables were (1) time since first treatment with CDs, (2) number of previous CDs, (3) age of present CDs, and (4) age at which first CDs were provided. The association between exposure variables and outcome was investigated using an ordinary least-square regression analysis, controlling for the effects of age.Age of current CDs, time since first CD, number of previous CDs, and the age at which CDs were first provided did not significantly influence OHRQoL. Regression coefficients for each exposure variable were, respectively, 0.0, 95% CI: -0.1 to 0.2; -0.1, 95% CI: -0.4 to 0.3; 0.8, 95% CI: -1.5 to 3.0, and 0.4, 95% CI: -0.1 to 0.8.The response to inevitable anatomic and biologic changes in the oral cavity related to edentulism, denture-wearing, age, and other factors does not necessarily translate rapidly into changes in perceived oral health in patients wearing CDs and maintaining a recall.

Sense of Belonging and Life Satisfaction among Hong Kong Adolescent Immigrants in Canada

This article attempts to disentangle the primary factors affecting Hong Kong adolescent immigrants’ life satisfaction and sense of belonging to Canada. A total of 368 participants attending 26 high schools under the jurisdiction of six school boards in Toronto took part in a self-administered questionnaire survey. Results of the multiple ordinary least-squares regression analysis indicated that presence of father in Canada, higher self-rated socio-economic status, immigration to Canada being politically and culturally motivated, positive experience in making friends with Canadians, immigration to Canada at a later stage in life, and no prior experience in Canada before immigration were associated with a stronger sense of belonging to Canada. On the other hand, positive experience in making friends with Canadians, positive academic experience, absence of discrimination experience, and immigration to Canada being non-economically motivated were associated with a markedly higher level of life satisfaction.

L‐asparaginase as a marker of chemotherapy dose modification in children with acute lymphoblastic leukemia

The objective of the current study was to compare chemotherapy dose modifications in obese (a body mass index [BMI] > 95%) and nonobese (a BMI < or = 95%) pediatric patients with acute lymphoblastic leukemia (ALL). The study cohort was comprised of 199 pediatric patients diagnosed with ALL who were treated at 1 of 2 South Texas pediatric oncology centers between 1990-2000. The relative chemotherapy dose modification during the induction phase of chemotherapy was calculated as the ratio of 1) the actual administered dose of L-asparaginase and 2) the protocol-calculated dose of L-asparaginase. The extent to which the chemotherapy dose modification varied according to obesity status was assessed using stratified Student t tests and an ordinary least-squares regression analysis. Obese ALL patients were found to exhibit a 7% decrease in the mean relative modification of L-asparaginase during induction chemotherapy compared with their nonobese counterparts. This finding was statistically significant (P = 0.009), even after adjustment for gender, age, ethnicity, and clinical institution. To the authors' knowledge, the current study is the first published report of an obesity-associated chemotherapy dose modification in pediatric patients with ALL, the most common childhood malignancy. It will be important to examine whether these findings are consistent with those observed in future studies, and ultimately to assess the association between obesity-related dose modifications and long-term cancer outcomes.

Patient- and ward-level determinants of nursing time in nursing facilities

To explore the patient- and ward-level determinants of wage-adjusted nursing time in long-term care wards for the elderly with a view to improving efficiency of the use of labour resources. The wage-adjusted nursing time given to patients was obtained from a time measurement study. Patient characteristics were based on the Minimum Data Set 2.0 of the Resident Assessment Instrument for nursing homes. Ordinary least-squares regression analysis and multilevel modelling were used to disentangle the effect of patient- and ward-level factors on nursing time. A significant difference in wage-adjusted nursing time between wards was detected, which was partly explained by characteristics of patients in wards. The combination of patients' physical functioning and cognition and the Resource Utilization Groups RUG-III/22 resource use classification explained 20-25% of patients' nursing time over a 24-hour period. Variables related to the operational environment of the ward did not explain differences in wage-adjusted nursing time once the patient profile of the ward had been controlled for. The results also showed notable unmeasured patient and ward level effects, inefficiency and randomness in the allocation of nursing time. By improving the allocation and use of labour resources, the substantial variation in nursing time between wards could be diminished. Managers should allocate their staff primarily according to patients' resource needs.

Comparing regression methods in estimation of biophysical properties of forest stands from two different inventories using laser scanner data

Mean tree height, dominant height, mean diameter, stem number, basal area, and timber volume of 233 field sample plots were estimated from various canopy height and canopy density metrics— derived by means of a small-footprint laser scanner over young and mature forest stands— using ordinary least-squares (OLS) regression analysis, seemingly unrelated regression (SUR), and partial least-squares (PLS) regression. The sample plots were distributed systematically throughout two separate inventory areas with size 1000 and 6500 ha, respectively. The plots were divided into three predefined strata. Separate regression models were estimated for each inventory as well as common models utilizing the plots of both inventories simultaneously. In the models estimated by combining data from the two areas, the statistical effect of inventory was found to be significant ( p<0.05) in the mean height models only. A total of 115 test stands and plots with size 0.3–11.7 ha were used to validate the estimated regression models. The bias and standard deviations (parenthesized) of the differences between predicted and ground reference values of mean height, dominant height, mean diameter, stem number, basal area, and volume were −5.5% to 4.7% (3.1–7.3%), −6.0% to 0.4% (2.9–8.2%), −0.2% to 7.9% (5.5–15.8%), −21.3% to 12.5% (13.4–29.3%), −7.3% to 8.4% (7.1–13.6%), and −3.9% to 10.1% (8.3–14.9%), respectively. It was revealed that only minor discrepancies occurred between the three investigated estimation techniques. None of the techniques provided predicted values that were superior to the other techniques over all combinations of strata and variables.

Fluoroquinolone Therapy for Uncomplicated Skin and Skin Structure Infections

Uncomplicated skin and skin structure infections (uSSSIs) are highly prevalent and costly. With the rising prevalence of bacterial resistance to older antibacterials, there has been an increase in the use of fluoroquinolones for the treatment of uSSSIs creating the need for comparative information. The objective of this study was to compare, under real-world conditions, the treatment duration, failure rates and treatment charges associated with initiation of outpatient treatment for uSSSIs with moxifloxacin versus levofloxacin. This retrospective study was conducted using claims data (April 1999 through March 2002) from the PharMetrics Patient-Centric Database. A cohort was created of patients who had treatment for a uSSSI that was initiated with either moxifloxacin or levofloxacin. The endpoints evaluated were: treatment duration, treatment failure and total charges. Logistic and ordinary least-squares regression analyses were used to test for differences among treatment groups whilst controlling for demographic and clinical characteristics. 506 patients were identified, representing 517 uSSSI treatment episodes. The mean durations of monotherapy and all antibacterial prescription therapy were significantly shorter for the moxifloxacin than the levofloxacin group (differences of 1.97 days [p = 0.015] and 1.60 days [p = 0.036], respectively). The original prescription duration, treatment failure rate and treatment charges were lower for the moxifloxacin group than the levofloxacin group, but differences were not statistically significant (p = 0.241, 0.395 and 0.199, respectively). In general, patients who initiated therapy for a uSSSI with moxifloxacin had a shorter duration of antibacterial therapy than those who initiated treatment with levofloxacin, with comparable treatment failure and cost outcomes. When a fluoroquinolone is required for the treatment of a uSSSI, moxi- floxacin (which is approved for 7-day therapy) provides comparable outcomes to levofloxacin under real-world conditions.

Life Satisfaction Among University Students in a Canadian Prairie City: a Multivariate Analysis

This article reports the findings from a questionnaire survey of university students’ life satisfaction in Regina. The results demonstrated that a significant proportion of the 315 respondents were satisfied with their lives (N = 240, 76.2%). With regard to degree of satisfaction with different aspects of life, respondents expressed that they were most satisfied with relationship with mother, living environment, relationships with close friends, relationships with siblings, and living arrangement. Multiple ordinary least-squares regression analyses revealed that respondents who indicated a higher socio-economic status, achieveda higher grade point average, and were more satisfied with their academic experience, self-esteem, relationship with significant other, and living conditions, expressed a markedly higher level of satisfaction with life.

Consumption and Saving Behavior of Older and Younger Baby Boomers in Korea

The 1998 Korean Survey of Family Income and Expenditures was used to examine the overall consumption and saving behavior of Korean baby boomers and compared the differences in consumption and saving behavior between older and younger boomers. The t -test results indicated that the younger boomers allocated a significantly higher percentage of their expenditures on food away from home, household appliances, transportation and communication than did the older boomers, whereas the older boomers spent higher amounts and allocated larger budget shares on their children's education than did the younger boomers. The results of Ordinary Least-Squares (OLS) regression analysis showed that, holding other factors constant, older boomers not only spent significantly more in the total consumption expenditures and education expenditures, but older boomers also saved significantly less than did younger boomers.

Under Performers and Over Achievers: A Quantile Regression Analysis of Growth

Numerous papers have searched for empirical linkages between long run economic growth and a myriad of economic, socio‐political and environmental factors. Most of these studies use ordinary least‐squares regression or panel regression analysis on a sample of countries and therefore consider the behaviour of growth around the mean of the conditional distribution. We extend the literature by using quantile regression to analyse long‐term growth at a variety of points in the conditional distribution. By using this approach, we identify the determinants of growth for under performing countries relative to those for over achieving countries.

A preliminary analysis of different approaches to preparing for the USMLE step 1.

RAJ A. THADANI, DAVID B. SWANSON, and ROBERT M. GALBRAITHPrior to taking the United States Medical Licensing Examination(USMLE) Step 1, medical students commonly spend large amountsof time studying on their own or in groups. They also may partic-ipate in test-preparation activities offered by their schools. In ad-dition, there is anecdotal evidence indicating that medical studentsincreasingly purchase ‘‘board prep’’ publications and sign up forcommercial coaching courses that may last several weeks and costthousands of dollars.The effectiveness of alternate approaches to preparing for Step1 is unknown, though research on other high-stakes exams suggeststhat exam performance may be improved by coaching courses.