Wanzhu Tu | Indiana University (original) (raw)

Papers by Wanzhu Tu

Research paper thumbnail of Performance of the PHQ-9 as a Screening Tool for Depression After Stroke

Background and Purpose—The purpose of this study was to examine the performance of the Patient He... more Background and Purpose—The purpose of this study was to examine the performance of the Patient Health Questionnaire (PHQ)-9, a 9-item depression scale, as a screening and diagnostic instrument for assessing depression in stroke survivors. Methods—As part of a randomized treatment trial for poststroke depression (PSD), subjects with and without PSD completed the PHQ-9, a 9-item summed scale, with scores ranging

Research paper thumbnail of A Comparison of Data Driven-based Measures of Adherence to Oral Hypoglycemic Agents in Medicaid Patients

AMIA ... Annual Symposium proceedings / AMIA Symposium. AMIA Symposium, 2014

We evaluated and compared different methods for measuring adherence to Oral Antihyperglycemic Age... more We evaluated and compared different methods for measuring adherence to Oral Antihyperglycemic Agents (OHA), based on the correlation between these measures and glycated hemoglobin A1C (HbA1c) levels in Medicaid patients with Type 2 diabetes. An observational sample of 831 Medicaid patients with Type 2 diabetes who had HbA1c test results recorded between January 1, 2001 and December 31, 2005 was identified in the Indiana Network of Patient Care (INPC). OHA adherence was measured by medication possession ratio (MPR), proportion of days covered (PDC), and the number of gaps (GAP) for 3, 6, and 12-month intervals prior to the HbA1c test date. All three OHA adherence measurements showed consistent and significant correlation with HbA1c level. The 6-month PDC showed the strongest association with HbA1c levels in both unadjusted (-1.07, P<0.0001) and adjusted (-1.12, P<0.0001) models.

Research paper thumbnail of Age Differences in the Association Between Body Mass Index Class and Annualized Medicare Expenditures

Journal of aging and health, Jan 25, 2015

The aim of the study is to assess the relationship between body mass index (BMI) class and Medica... more The aim of the study is to assess the relationship between body mass index (BMI) class and Medicare claims among young-old (65-69), old (70-74), and old-old (75+) adults over a 10-year period. We assessed costs by BMI class and age group among 9,300 respondents to the 1998 Health and Retirement Study (HRS) with linked 1998-2008 Medicare claims data. BMI was classified as normal (18.5-24.9), overweight (25-29.9), mild obesity (30-34.9), or severe obesity (35 or above). Annualized total Medicare claims adjusted for age, gender, ethnicity, education, and smoking history were 109% greater for severely obese young-old adults in comparison with normal weight young-old adults (US$9,751 vs. US$4,663). Total annualized claim differences between the normal weight and severely obese in the old and old-old groups were not statistically significant. Excess Medicare expenditures related to obesity may be concentrated among severely obese young-old adults. Preventing severe obesity among middle an...

Research paper thumbnail of Association of Condom Use, Sexual Behaviors, and Sexually Transmitted Infections With the Duration of Genital Human Papillomavirus Infection Among Adolescent Women

were used to assess the effects of risk factors on the dura- tion of HPV infection. Because viral... more were used to assess the effects of risk factors on the dura- tion of HPV infection. Because viral clearance is a pre- ferred outcome, a variable with an AHR less than 1 was considered a risk factor (ie, associated with reduced chance of viral clearance and prolonged infection). Results: Prolonged HPV infection was associated with oncogenic HPV types (AHR, 0.58

Research paper thumbnail of Time From First Intercourse to First Sexually Transmitted Infection Diagnosis Among Adolescent Women

Research paper thumbnail of Association between adherence measurements of metoprolol and health care utilization in older patients with heart failure

Clinical pharmacology and therapeutics, 2005

Data from electronic dosing monitors and published pharmacokinetic parameters were used to derive... more Data from electronic dosing monitors and published pharmacokinetic parameters were used to derive medication adherence measures for immediate-release metoprolol and examine their association with health care utilization of outpatients aged 50 years or older with heart failure. We used a 1-compartment model and published population pharmacokinetic parameters to estimate mean plasma metoprolol concentrations for patients treated for 6 to 12 months. In the absence of directly measured plasma concentrations, we calculated the intended mean plasma concentration (Cp'(ave)) under the assumption of perfect adherence to the prescribed dose and frequency of administration. Projected mean plasma concentrations (Cp(ave)) were estimated by use of data from recorded dosing times. In addition to taking adherence (percentage of dose taken) and scheduling adherence (percentage of doses taken on schedule), we calculated the deviation from the intended exposure (DeltaCp(ave) = Cp'(ave) - Cp(av...

Research paper thumbnail of Associations Between Menarche-Related Genetic Variants and Pubertal Growth in Male and Female Adolescents

Journal of Adolescent Health, 2015

Previous studies have identified novel genetic variants associated with age at menarche in female... more Previous studies have identified novel genetic variants associated with age at menarche in females of European descent. The pubertal growth effects of these variants have not been carefully evaluated in non-European descent groups. We aimed to examine the effects of 31 newly identified menarche-related single-nucleotide polymorphisms (SNPs) on growth outcomes in African-American (AA) and European-American (EA) children in a prospective cohort. We analyzed longitudinal data collected from 263 AAs and 338 EAs enrolled between ages 5 and 17 years; the subjects were followed semiannually for an average of 6 years. The associations between the SNPs and growth-related outcomes, including weight, height, and body mass index (BMI), were examined using mixed-effect models. Longitudinal analyses revealed that 4 (near or in genes VGLL3, PEX2, CA10, and SKOR2) of the 14 menarche-only-related SNPs were associated with changes in weight and BMI in EA and AA (p ≤ .0032), but none of them was associated with changes in height. Of the eight menarche-timing and BMI-related SNPs, none was associated with changes in height, but three (in or near genes NEGR1, ETV5, and FTO) were associated with more rapid increases in weight and/or BMI in EA (p ≤ .0059). Among the nine menarche-timing and height-related SNPs, four (in or near genes ZBTB38, LOC728666, TBX2, and CABLES) were associated with changes in weight or height in EA and AA (p ≤ .0042). Genetic variants related to age at menarche were found to be associated with various growth parameters in healthy adolescents. The identified associations were often race and sex specific.

Research paper thumbnail of Correlates of Health Literacy in Patients With Chronic Heart Failure

in health literacy. Implications: The association of cognitive abilities and literacy has importa... more in health literacy. Implications: The association of cognitive abilities and literacy has important implica- tions for health literacy models and for interventions to reduce the impact of low health literacy on health outcomes.Forexample,medicationinstructionsshould be designed to reduce comprehension demands on general cognitive abilities as well as literacy skills.

Research paper thumbnail of Estimation of survival functions in interval and right censored data using STD behavioural diaries

Statistics in Medicine, 2006

In investigations of sexually transmitted diseases (STDs), true infection times are often either ... more In investigations of sexually transmitted diseases (STDs), true infection times are often either interval censored or right censored. For such data, reliable estimation of the survival function is difficult to obtain. In this research, we propose a resampling based method for the estimation of the survival function using auxiliary behavioural information provided by daily diaries. By imputing the unknown infection time from a list of sexual encounter times recorded in the diaries, the proposed procedure can be easily implemented using existing estimation procedures for right censored data. Our simulations show that the proposed procedure consistently outperforms the existing ad hoc estimation methods and produces smaller mean integrated squared errors (MISE). We illustrate this method by analysing infection data obtained from an ongoing STD investigation of adolescent females.

Research paper thumbnail of A semi-parametric threshold regression analysis of sexually transmitted infections in adolescent women

Statistics in Medicine, 2009

Time-to-event analysis of sexually transmitted infection data is often complicated by the existen... more Time-to-event analysis of sexually transmitted infection data is often complicated by the existence of nonproportional hazards and nonlinear independent variable effects. Methods without the proportional hazards assumption, such as threshold regression models, have been successfully used in many applications. This paper seeks to extend the existing threshold regression models to accommodate the nonlinear independent variable effects. Specifically, we incorporated penalized and regression splines to the threshold regression models for added modeling flexibility. Cross validation methods were used for the selection of the number of knots and for the determination of smoothing parameters. Variance estimates were proposed for inference purposes. Simulation results showed that the proposed methods were able to achieve nonparametric function and parametric coefficient estimates that are close to their true values. Simulation also demonstrated satisfactory performance of variance estimates. Using the proposed methods, we analyzed time from sexual debut to the first infection with Chlamydia trachomatis infection in a group of young women. Analysis shows that the lifetime number of sexual partners has a nonlinear effect on the risk of C. trachomatis infection and the infection risks were differential by ethnicity and age of sexual debut.

Research paper thumbnail of The Prevalence of Chlamydia, Gonorrhea, and Trichomonas in Sexual Partnerships: Implications for Partner Notification and Treatment

Sexually Transmitted Diseases, 2005

Research paper thumbnail of The use of propensity scores in pharmacoepidemiologic research

Pharmacoepidemiology and Drug Safety, 2000

Research paper thumbnail of A stochastic model for assessing Chlamydia trachomatis transmission risk by using longitudinal observational data

Journal of the Royal Statistical Society: Series A (Statistics in Society), 2011

Research paper thumbnail of Genetic Variation in Cyp4A11 and Blood Pressure Response to Mineralocorticoid Receptor Antagonism or Enac Inhibition: an Exploratory Pilot Study in African Americans

Journal of the American Society of Hypertension, 2014

Research paper thumbnail of Cancer-Related Pain and Disability: A Longitudinal Study

Journal of Pain and Symptom Management, 2011

Research paper thumbnail of A Longitudinal Study of Genital Human Papillomavirus Infection in a Cohort of Closely Followed Adolescent Women

The Journal of Infectious Diseases, 2005

Research paper thumbnail of Repeated Chlamydia trachomatis Genital Infections in Adolescent Women

The Journal of Infectious Diseases, 2010

Research paper thumbnail of Synchronization of Adolescent Blood Pressure and Pubertal Somatic Growth

The Journal of Clinical Endocrinology & Metabolism, 2009

Blood pressure (BP) and growth increase at an accelerated rate during puberty. The temporal relat... more Blood pressure (BP) and growth increase at an accelerated rate during puberty. The temporal relationship of the two events has not been well characterized. The purpose of this current investigation was to examine the rate of BP change in relation to pubertal growth with the intent to shed light on new mechanisms by which BP is regulated. We examined data from a cohort of 182 normotensive children who had measurements made semiannually for up to 12 yr. From the recorded heights, we identified the subject-specific pubertal growth spurt (PGS) using a growth curve model. With the estimated PGS as an anchoring point, we obtained the rates at which BP and weight changed as continuous functions of time for the duration of pubertal growth. Examining BP on a scale relative to PGS placed BP development in the context of pubertal growth. Average ages at PGS were 11.5 for girls and 13.3 for boys. Fitted spline models estimated that at the time of PGS, the mean systolic BP was 100 mm Hg for girls and 107 mm Hg for boys; the mean diastolic BP at the PGS was 59 mm Hg for girls and 61 mm Hg for boys. The most intriguing observation was that rate of change in systolic BP and weight peaked at precisely the estimated PGS. The time synchronization of rates of change in BP, weight, and height suggests common regulating mechanisms for somatic growth and BP or growth changes that secondarily affect BP.

Research paper thumbnail of Improving the Validity of Activity of Daily Living Dependency Risk Assessment

Journal of Applied Gerontology, 2013

Objectives:Efforts to prevent activity of daily living (ADL) dependency may be improved through m... more Objectives:Efforts to prevent activity of daily living (ADL) dependency may be improved through models that assess older adults&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; dependency risk. We evaluated whether cognition and gait speed measures improve the predictive validity of interview-based models.Method:Participants were 8,095 self-respondents in the 2006 Health and Retirement Survey who were aged 65 years or over and independent in five ADLs. Incident ADL dependency was determined from the 2008 interview. Models were developed using random 2/3rd cohorts and validated in the remaining 1/3rd.Results:Compared to a c-statistic of 0.79 in the best interview model, the model including cognitive measures had c-statistics of 0.82 and 0.80 while the best fitting gait speed model had c-statistics of 0.83 and 0.79 in the development and validation cohorts, respectively.Conclusion:Two relatively brief models, one that requires an in-person assessment and one that does not, had excellent validity for predicting incident ADL dependency but did not significantly improve the predictive validity of the best fitting interview-based models.

Research paper thumbnail of 2: Emotional & behavioral attributes of casual friends, good friends & boyfriends

Journal of Adolescent Health, 2007

Research paper thumbnail of Performance of the PHQ-9 as a Screening Tool for Depression After Stroke

Background and Purpose—The purpose of this study was to examine the performance of the Patient He... more Background and Purpose—The purpose of this study was to examine the performance of the Patient Health Questionnaire (PHQ)-9, a 9-item depression scale, as a screening and diagnostic instrument for assessing depression in stroke survivors. Methods—As part of a randomized treatment trial for poststroke depression (PSD), subjects with and without PSD completed the PHQ-9, a 9-item summed scale, with scores ranging

Research paper thumbnail of A Comparison of Data Driven-based Measures of Adherence to Oral Hypoglycemic Agents in Medicaid Patients

AMIA ... Annual Symposium proceedings / AMIA Symposium. AMIA Symposium, 2014

We evaluated and compared different methods for measuring adherence to Oral Antihyperglycemic Age... more We evaluated and compared different methods for measuring adherence to Oral Antihyperglycemic Agents (OHA), based on the correlation between these measures and glycated hemoglobin A1C (HbA1c) levels in Medicaid patients with Type 2 diabetes. An observational sample of 831 Medicaid patients with Type 2 diabetes who had HbA1c test results recorded between January 1, 2001 and December 31, 2005 was identified in the Indiana Network of Patient Care (INPC). OHA adherence was measured by medication possession ratio (MPR), proportion of days covered (PDC), and the number of gaps (GAP) for 3, 6, and 12-month intervals prior to the HbA1c test date. All three OHA adherence measurements showed consistent and significant correlation with HbA1c level. The 6-month PDC showed the strongest association with HbA1c levels in both unadjusted (-1.07, P<0.0001) and adjusted (-1.12, P<0.0001) models.

Research paper thumbnail of Age Differences in the Association Between Body Mass Index Class and Annualized Medicare Expenditures

Journal of aging and health, Jan 25, 2015

The aim of the study is to assess the relationship between body mass index (BMI) class and Medica... more The aim of the study is to assess the relationship between body mass index (BMI) class and Medicare claims among young-old (65-69), old (70-74), and old-old (75+) adults over a 10-year period. We assessed costs by BMI class and age group among 9,300 respondents to the 1998 Health and Retirement Study (HRS) with linked 1998-2008 Medicare claims data. BMI was classified as normal (18.5-24.9), overweight (25-29.9), mild obesity (30-34.9), or severe obesity (35 or above). Annualized total Medicare claims adjusted for age, gender, ethnicity, education, and smoking history were 109% greater for severely obese young-old adults in comparison with normal weight young-old adults (US$9,751 vs. US$4,663). Total annualized claim differences between the normal weight and severely obese in the old and old-old groups were not statistically significant. Excess Medicare expenditures related to obesity may be concentrated among severely obese young-old adults. Preventing severe obesity among middle an...

Research paper thumbnail of Association of Condom Use, Sexual Behaviors, and Sexually Transmitted Infections With the Duration of Genital Human Papillomavirus Infection Among Adolescent Women

were used to assess the effects of risk factors on the dura- tion of HPV infection. Because viral... more were used to assess the effects of risk factors on the dura- tion of HPV infection. Because viral clearance is a pre- ferred outcome, a variable with an AHR less than 1 was considered a risk factor (ie, associated with reduced chance of viral clearance and prolonged infection). Results: Prolonged HPV infection was associated with oncogenic HPV types (AHR, 0.58

Research paper thumbnail of Time From First Intercourse to First Sexually Transmitted Infection Diagnosis Among Adolescent Women

Research paper thumbnail of Association between adherence measurements of metoprolol and health care utilization in older patients with heart failure

Clinical pharmacology and therapeutics, 2005

Data from electronic dosing monitors and published pharmacokinetic parameters were used to derive... more Data from electronic dosing monitors and published pharmacokinetic parameters were used to derive medication adherence measures for immediate-release metoprolol and examine their association with health care utilization of outpatients aged 50 years or older with heart failure. We used a 1-compartment model and published population pharmacokinetic parameters to estimate mean plasma metoprolol concentrations for patients treated for 6 to 12 months. In the absence of directly measured plasma concentrations, we calculated the intended mean plasma concentration (Cp'(ave)) under the assumption of perfect adherence to the prescribed dose and frequency of administration. Projected mean plasma concentrations (Cp(ave)) were estimated by use of data from recorded dosing times. In addition to taking adherence (percentage of dose taken) and scheduling adherence (percentage of doses taken on schedule), we calculated the deviation from the intended exposure (DeltaCp(ave) = Cp'(ave) - Cp(av...

Research paper thumbnail of Associations Between Menarche-Related Genetic Variants and Pubertal Growth in Male and Female Adolescents

Journal of Adolescent Health, 2015

Previous studies have identified novel genetic variants associated with age at menarche in female... more Previous studies have identified novel genetic variants associated with age at menarche in females of European descent. The pubertal growth effects of these variants have not been carefully evaluated in non-European descent groups. We aimed to examine the effects of 31 newly identified menarche-related single-nucleotide polymorphisms (SNPs) on growth outcomes in African-American (AA) and European-American (EA) children in a prospective cohort. We analyzed longitudinal data collected from 263 AAs and 338 EAs enrolled between ages 5 and 17 years; the subjects were followed semiannually for an average of 6 years. The associations between the SNPs and growth-related outcomes, including weight, height, and body mass index (BMI), were examined using mixed-effect models. Longitudinal analyses revealed that 4 (near or in genes VGLL3, PEX2, CA10, and SKOR2) of the 14 menarche-only-related SNPs were associated with changes in weight and BMI in EA and AA (p ≤ .0032), but none of them was associated with changes in height. Of the eight menarche-timing and BMI-related SNPs, none was associated with changes in height, but three (in or near genes NEGR1, ETV5, and FTO) were associated with more rapid increases in weight and/or BMI in EA (p ≤ .0059). Among the nine menarche-timing and height-related SNPs, four (in or near genes ZBTB38, LOC728666, TBX2, and CABLES) were associated with changes in weight or height in EA and AA (p ≤ .0042). Genetic variants related to age at menarche were found to be associated with various growth parameters in healthy adolescents. The identified associations were often race and sex specific.

Research paper thumbnail of Correlates of Health Literacy in Patients With Chronic Heart Failure

in health literacy. Implications: The association of cognitive abilities and literacy has importa... more in health literacy. Implications: The association of cognitive abilities and literacy has important implica- tions for health literacy models and for interventions to reduce the impact of low health literacy on health outcomes.Forexample,medicationinstructionsshould be designed to reduce comprehension demands on general cognitive abilities as well as literacy skills.

Research paper thumbnail of Estimation of survival functions in interval and right censored data using STD behavioural diaries

Statistics in Medicine, 2006

In investigations of sexually transmitted diseases (STDs), true infection times are often either ... more In investigations of sexually transmitted diseases (STDs), true infection times are often either interval censored or right censored. For such data, reliable estimation of the survival function is difficult to obtain. In this research, we propose a resampling based method for the estimation of the survival function using auxiliary behavioural information provided by daily diaries. By imputing the unknown infection time from a list of sexual encounter times recorded in the diaries, the proposed procedure can be easily implemented using existing estimation procedures for right censored data. Our simulations show that the proposed procedure consistently outperforms the existing ad hoc estimation methods and produces smaller mean integrated squared errors (MISE). We illustrate this method by analysing infection data obtained from an ongoing STD investigation of adolescent females.

Research paper thumbnail of A semi-parametric threshold regression analysis of sexually transmitted infections in adolescent women

Statistics in Medicine, 2009

Time-to-event analysis of sexually transmitted infection data is often complicated by the existen... more Time-to-event analysis of sexually transmitted infection data is often complicated by the existence of nonproportional hazards and nonlinear independent variable effects. Methods without the proportional hazards assumption, such as threshold regression models, have been successfully used in many applications. This paper seeks to extend the existing threshold regression models to accommodate the nonlinear independent variable effects. Specifically, we incorporated penalized and regression splines to the threshold regression models for added modeling flexibility. Cross validation methods were used for the selection of the number of knots and for the determination of smoothing parameters. Variance estimates were proposed for inference purposes. Simulation results showed that the proposed methods were able to achieve nonparametric function and parametric coefficient estimates that are close to their true values. Simulation also demonstrated satisfactory performance of variance estimates. Using the proposed methods, we analyzed time from sexual debut to the first infection with Chlamydia trachomatis infection in a group of young women. Analysis shows that the lifetime number of sexual partners has a nonlinear effect on the risk of C. trachomatis infection and the infection risks were differential by ethnicity and age of sexual debut.

Research paper thumbnail of The Prevalence of Chlamydia, Gonorrhea, and Trichomonas in Sexual Partnerships: Implications for Partner Notification and Treatment

Sexually Transmitted Diseases, 2005

Research paper thumbnail of The use of propensity scores in pharmacoepidemiologic research

Pharmacoepidemiology and Drug Safety, 2000

Research paper thumbnail of A stochastic model for assessing Chlamydia trachomatis transmission risk by using longitudinal observational data

Journal of the Royal Statistical Society: Series A (Statistics in Society), 2011

Research paper thumbnail of Genetic Variation in Cyp4A11 and Blood Pressure Response to Mineralocorticoid Receptor Antagonism or Enac Inhibition: an Exploratory Pilot Study in African Americans

Journal of the American Society of Hypertension, 2014

Research paper thumbnail of Cancer-Related Pain and Disability: A Longitudinal Study

Journal of Pain and Symptom Management, 2011

Research paper thumbnail of A Longitudinal Study of Genital Human Papillomavirus Infection in a Cohort of Closely Followed Adolescent Women

The Journal of Infectious Diseases, 2005

Research paper thumbnail of Repeated Chlamydia trachomatis Genital Infections in Adolescent Women

The Journal of Infectious Diseases, 2010

Research paper thumbnail of Synchronization of Adolescent Blood Pressure and Pubertal Somatic Growth

The Journal of Clinical Endocrinology & Metabolism, 2009

Blood pressure (BP) and growth increase at an accelerated rate during puberty. The temporal relat... more Blood pressure (BP) and growth increase at an accelerated rate during puberty. The temporal relationship of the two events has not been well characterized. The purpose of this current investigation was to examine the rate of BP change in relation to pubertal growth with the intent to shed light on new mechanisms by which BP is regulated. We examined data from a cohort of 182 normotensive children who had measurements made semiannually for up to 12 yr. From the recorded heights, we identified the subject-specific pubertal growth spurt (PGS) using a growth curve model. With the estimated PGS as an anchoring point, we obtained the rates at which BP and weight changed as continuous functions of time for the duration of pubertal growth. Examining BP on a scale relative to PGS placed BP development in the context of pubertal growth. Average ages at PGS were 11.5 for girls and 13.3 for boys. Fitted spline models estimated that at the time of PGS, the mean systolic BP was 100 mm Hg for girls and 107 mm Hg for boys; the mean diastolic BP at the PGS was 59 mm Hg for girls and 61 mm Hg for boys. The most intriguing observation was that rate of change in systolic BP and weight peaked at precisely the estimated PGS. The time synchronization of rates of change in BP, weight, and height suggests common regulating mechanisms for somatic growth and BP or growth changes that secondarily affect BP.

Research paper thumbnail of Improving the Validity of Activity of Daily Living Dependency Risk Assessment

Journal of Applied Gerontology, 2013

Objectives:Efforts to prevent activity of daily living (ADL) dependency may be improved through m... more Objectives:Efforts to prevent activity of daily living (ADL) dependency may be improved through models that assess older adults&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; dependency risk. We evaluated whether cognition and gait speed measures improve the predictive validity of interview-based models.Method:Participants were 8,095 self-respondents in the 2006 Health and Retirement Survey who were aged 65 years or over and independent in five ADLs. Incident ADL dependency was determined from the 2008 interview. Models were developed using random 2/3rd cohorts and validated in the remaining 1/3rd.Results:Compared to a c-statistic of 0.79 in the best interview model, the model including cognitive measures had c-statistics of 0.82 and 0.80 while the best fitting gait speed model had c-statistics of 0.83 and 0.79 in the development and validation cohorts, respectively.Conclusion:Two relatively brief models, one that requires an in-person assessment and one that does not, had excellent validity for predicting incident ADL dependency but did not significantly improve the predictive validity of the best fitting interview-based models.

Research paper thumbnail of 2: Emotional & behavioral attributes of casual friends, good friends & boyfriends

Journal of Adolescent Health, 2007