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Research paper thumbnail of Design and baseline characteristics of participants in the TRial of Economic Incentives to Promote Physical Activity (TRIPPA): A randomized controlled trial of a six month pedometer program with financial incentives

Contemporary clinical trials, Jan 7, 2015

Non-communicable diseases (NCDs) are emerging as the predominant global health challenge of this ... more Non-communicable diseases (NCDs) are emerging as the predominant global health challenge of this century. Physical inactivity is one of the primary risk factors for NCDs. Therefore, increasing physical activity levels is a public health imperative. The arrival of affordable wearable technologies, such as wireless pedometers, provides one strategy for encouraging walking. However, the effectiveness of these technologies in promoting sustained behavior change has not been established. Insights from economics suggest that incentives may be a useful strategy for increasing maintenance and effectiveness of behavior change interventions, including physical activity interventions that rely on wearable technologies. The aim of this trial is to test the effectiveness of a common wireless pedometer with or without one of two types of incentives (cash or donations to charity) for reaching weekly physical activity goals. We present here the design and baseline characteristics of participants of...

Research paper thumbnail of Lamina cribrosa visibility using optical coherence tomography: comparison of devices and effects of image enhancement techniques

Investigative ophthalmology & visual science, 2015

To compare the visibility of the lamina cribrosa (LC) in optic disc images acquired from 60 glauc... more To compare the visibility of the lamina cribrosa (LC) in optic disc images acquired from 60 glaucoma and 60 control subjects using three optical coherence tomography (OCT) devices, with and without enhanced depth imaging (EDI) and adaptive compensation (AC). A horizontal B-scan was acquired through the center of the disc using two spectral-domain (Spectralis and Cirrus; with and without EDI) and a swept-source (DRI) OCT. Adaptive compensation was applied post acquisition to improve image quality. To assess LC visibility, four masked observers graded the 1200 images in a randomized sequence. The anterior LC was graded from 0 to 4, the LC insertions from 0 to 2, and the posterior LC either 0 or 1. The effect of EDI, AC, glaucoma severity, and other clinical/demographic factors on LC visibility was assessed using generalized estimating equations. The anterior LC was the most detectable feature, followed by the LC insertions. Adaptive compensation improved anterior LC visibility indepen...

Research paper thumbnail of INTERVENTIONAL STRATEGIES ASSOCIATED WITH IMPROVEMENTS IN SURVIVAL FOR OUT-OF-HOSPITAL CARDIAC ARRESTS IN SINGAPORE OVER 10 YEARS

Resuscitation, 2015

We aim to study if there has been an improvement in survival for Out-of-Hospital Cardiac Arrest (... more We aim to study if there has been an improvement in survival for Out-of-Hospital Cardiac Arrest (OHCA) in Singapore, the effects of various interventional strategies over the past 10 years, and identify strategies that contributed to improved survival. Rates of OHCA survival were compared between 2001-2004 and 2010-2012, using nationwide data for all OHCA presenting to EMS and public hospitals. A multivariate logistic regression model for survival to discharge was constructed to identify strategies with significant impact. A total of 5453 cases were included, 2428 cases from 2001 to 2004 and 3025 cases from 2010 to 2012. There was significant improvement in Utstein (witnessed, shockable) survival to discharge from 2001-2004 (2.5%) to 2010-2012 (11.0%), adjusted odds ratio (OR) 9.6 [95% CI: 2.2-41.9]). Overall survival to discharge increased from 1.6% to 3.2% (adjusted OR 2.2 [1.5-3.3]). Bystander CPR rates increased from 19.7% to 22.4% (p=0.02). The multivariate regression model (adjusted for important non-modifiable risk factors) showed that response time <8min (OR 1.5 [1.0-2.3]), bystander AED (OR 5.8 [2.0-16.2]), and post-resuscitation hypothermia (OR 30.0 [11.5-78.0]) were significantly associated with survival to hospital discharge. Conversely, pre-hospital epinephrine (OR 0.6 [0.4-0.9]) was associated negatively with survival. OHCA survival has improved in Singapore over the past 10 years. Improvement in response time, public AEDs and post-resuscitation hypothermia appear to have contributed to the increase in survival. Singapore's experience might suggest that developing EMS systems should focus on reducing times to basic life support, including bystander defibrillation and post-resuscitation care.

Research paper thumbnail of Prediction of adverse cardiac events in emergency department patients with chest pain using machine learning for variable selection

BMC Medical Informatics and Decision Making, 2014

Research paper thumbnail of Validation of a risk scoring model for prediction of acute cardiac complications in chest pain patients presenting to the Emergency Department

International Journal of Cardiology, 2014

Research paper thumbnail of Cost-Effectiveness of an Injury and Drowning Prevention Program in Bangladesh

Research paper thumbnail of Randomized Clinical Trial of Cutting Balloon Angioplasty versus High-Pressure Balloon Angioplasty in Hemodialysis Arteriovenous Fistula Stenoses Resistant to Conventional Balloon Angioplasty

Journal of Vascular and Interventional Radiology, 2014

Research paper thumbnail of Expert estimates of caregiver hours for older Singaporeans with dementia

Australasian Journal on Ageing, 2012

To obtain experts&amp... more To obtain experts' estimates of the number of non-medical care hours required by older Singaporeans at different stages of ageing-related dementia, with low or high behavioural features. Experts on dementia in Singapore attended one of two meetings where they provided estimates of the number of care hours required for individuals at mild, moderate and severe levels of dementia with either low or high behavioural features. The experts were shown the collated responses, given an opportunity to discuss as a group, and then polled again. The estimated mean care hours varied by dementia severity and the level of behavioural features. There was no interaction between dementia severity and behavioural features. Estimated care hours needed by individuals with dementia is independently influenced by severity of dementia and behavioural features. These estimates may be useful for policy-makers in projecting the impact of caregiving.

Research paper thumbnail of Ultrasound Imaging of Normal Displacement of the Extensor Carpi Ulnaris Tendon Within the Ulnar Groove in 12 Forearm–Wrist Positions

American Journal of Roentgenology, 2009

Instability of the extensor carpi ulnaris (ECU) tendon can be a difficult clinical diagnosis beca... more Instability of the extensor carpi ulnaris (ECU) tendon can be a difficult clinical diagnosis because of normal changes in tendon position during wrist motion. Our goal was to determine the normal variation of ECU tendon displacement in 12 forearm-wrist positions. Ultrasound imaging of the ECU tendons of 40 symptom-free wrists of healthy volunteers (13 women, seven men; mean age, 22.3 years; range, 20-25 years) was performed. Each ECU tendon was examined in 12 positions: four wrist positions (ulnar deviation, radial deviation, flexion, and extension) in each of three forearm positions (pronation, supination, and neutral). ECU tendon displacement in the right hand was not significantly different from that in the left, and displacement in men did not differ significantly from that in women. There was a small but significant difference between displacement in the dominant and that in the nondominant hand (p < 0.02). Mean ECU tendon displacement was greatest in the supinated forearm position (p < 0.001) followed by the neutral position (p < 0.001) and was least in the pronated position (p < 0.001). Both ulnar deviation (p < 0.001) and flexion (p < 0.002) were associated with greater ECU tendon displacement than were radial deviation (p…

Research paper thumbnail of Clinical and MRI Findings Associated with False-Positive Knee MR Diagnoses of Medial Meniscal Tears

American Journal of Roentgenology, 2008

The objective of our study was to determine if false-positive MR diagnoses of a medial meniscal t... more The objective of our study was to determine if false-positive MR diagnoses of a medial meniscal tear are more common with specific clinical variables, tear type or location, or MRI findings of a longitudinal tear. We reviewed the records of 559 patients who underwent knee MR examinations and arthroscopy. We compared the positive predictive values (PPVs) of an MR diagnosis of a medial meniscal tear for differences in tear location or type, delay between knee injury and MRI, delay between MRI and arthroscopy, and the presence of an anterior cruciate ligament (ACL) tear. We also retrospectively reviewed the MR examinations of 50 longitudinal tears to compare the PPVs of various MRI findings of a longitudinal tear. There was no association between either the delay between injury and MRI or the delay between MRI and arthroscopy and false-positive diagnoses. The PPV of 64% (32/50) for longitudinal tears was lower than the values of 83% (15/18) to 100% (116/116) for other types of medial meniscal tears. False-positive diagnoses of medial meniscal tears were more common in patients who had a prior episode of acute trauma (p = 0.004) or an ACL tear (p < 0.0001). Review of longitudinal tears revealed a decreased PPV when MRI showed signal contacting only the superior surface (p = 0.016) or when MRI showed signal contacting the surface at the meniscocapsular junction (p = 0.004). Four of the 18 menisci with a false-positive diagnosis of a longitudinal tear had a healed ACL tear noted at arthroscopy. False-positive MR diagnoses of medial meniscal tears are more common for longitudinal tears than other tear types and are also more common with MR abnormalities at either the superior surface or the meniscocapsular junction. Spontaneous healing of longitudinal tears accounts for some false-positive MR diagnoses.

Research paper thumbnail of Development of a Score and Probability Estimate for Detecting Angle Closure Based on Anterior Segment Optical Coherence Tomography

American Journal of Ophthalmology, 2014

To develop a score along with an estimated probability of disease for detecting angle closure bas... more To develop a score along with an estimated probability of disease for detecting angle closure based on anterior segment optical coherence tomography (AS OCT) imaging. Cross-sectional study. A total of 2047 subjects 50 years of age and older were recruited from a community polyclinic in Singapore. All subjects underwent standardized ocular examination including gonioscopy and imaging by AS OCT (Carl Zeiss Meditec). Customized software (Zhongshan Angle Assessment Program) was used to measure AS OCT parameters. Complete data were available for 1368 subjects. Data from the right eyes were used for analysis. A stepwise logistic regression model with Akaike information criterion was used to generate a score that then was converted to an estimated probability of the presence of gonioscopic angle closure, defined as the inability to visualize the posterior trabecular meshwork for at least 180 degrees on nonindentation gonioscopy. Of the 1368 subjects, 295 (21.6%) had gonioscopic angle closure. The angle closure score was calculated from the shifted linear combination of the AS OCT parameters. The score can be converted to an estimated probability of having angle closure using the relationship: estimated probability = e(score)/(1 + e(score)), where e is the natural exponential. The score performed well in a second independent sample of 178 angle-closure subjects and 301 normal controls, with an area under the receiver operating characteristic curve of 0.94. A score derived from a single AS OCT image, coupled with an estimated probability, provides an objective platform for detection of angle closure.

Research paper thumbnail of Risk stratification for prediction of adverse coronary events in emergency department chest pain patients with a machine learning score compared with the TIMI score

International Journal of Cardiology, 2014

Research paper thumbnail of Design and baseline characteristics of participants in the TRial of Economic Incentives to Promote Physical Activity (TRIPPA): A randomized controlled trial of a six month pedometer program with financial incentives

Contemporary clinical trials, Jan 7, 2015

Non-communicable diseases (NCDs) are emerging as the predominant global health challenge of this ... more Non-communicable diseases (NCDs) are emerging as the predominant global health challenge of this century. Physical inactivity is one of the primary risk factors for NCDs. Therefore, increasing physical activity levels is a public health imperative. The arrival of affordable wearable technologies, such as wireless pedometers, provides one strategy for encouraging walking. However, the effectiveness of these technologies in promoting sustained behavior change has not been established. Insights from economics suggest that incentives may be a useful strategy for increasing maintenance and effectiveness of behavior change interventions, including physical activity interventions that rely on wearable technologies. The aim of this trial is to test the effectiveness of a common wireless pedometer with or without one of two types of incentives (cash or donations to charity) for reaching weekly physical activity goals. We present here the design and baseline characteristics of participants of...

Research paper thumbnail of Lamina cribrosa visibility using optical coherence tomography: comparison of devices and effects of image enhancement techniques

Investigative ophthalmology & visual science, 2015

To compare the visibility of the lamina cribrosa (LC) in optic disc images acquired from 60 glauc... more To compare the visibility of the lamina cribrosa (LC) in optic disc images acquired from 60 glaucoma and 60 control subjects using three optical coherence tomography (OCT) devices, with and without enhanced depth imaging (EDI) and adaptive compensation (AC). A horizontal B-scan was acquired through the center of the disc using two spectral-domain (Spectralis and Cirrus; with and without EDI) and a swept-source (DRI) OCT. Adaptive compensation was applied post acquisition to improve image quality. To assess LC visibility, four masked observers graded the 1200 images in a randomized sequence. The anterior LC was graded from 0 to 4, the LC insertions from 0 to 2, and the posterior LC either 0 or 1. The effect of EDI, AC, glaucoma severity, and other clinical/demographic factors on LC visibility was assessed using generalized estimating equations. The anterior LC was the most detectable feature, followed by the LC insertions. Adaptive compensation improved anterior LC visibility indepen...

Research paper thumbnail of INTERVENTIONAL STRATEGIES ASSOCIATED WITH IMPROVEMENTS IN SURVIVAL FOR OUT-OF-HOSPITAL CARDIAC ARRESTS IN SINGAPORE OVER 10 YEARS

Resuscitation, 2015

We aim to study if there has been an improvement in survival for Out-of-Hospital Cardiac Arrest (... more We aim to study if there has been an improvement in survival for Out-of-Hospital Cardiac Arrest (OHCA) in Singapore, the effects of various interventional strategies over the past 10 years, and identify strategies that contributed to improved survival. Rates of OHCA survival were compared between 2001-2004 and 2010-2012, using nationwide data for all OHCA presenting to EMS and public hospitals. A multivariate logistic regression model for survival to discharge was constructed to identify strategies with significant impact. A total of 5453 cases were included, 2428 cases from 2001 to 2004 and 3025 cases from 2010 to 2012. There was significant improvement in Utstein (witnessed, shockable) survival to discharge from 2001-2004 (2.5%) to 2010-2012 (11.0%), adjusted odds ratio (OR) 9.6 [95% CI: 2.2-41.9]). Overall survival to discharge increased from 1.6% to 3.2% (adjusted OR 2.2 [1.5-3.3]). Bystander CPR rates increased from 19.7% to 22.4% (p=0.02). The multivariate regression model (adjusted for important non-modifiable risk factors) showed that response time <8min (OR 1.5 [1.0-2.3]), bystander AED (OR 5.8 [2.0-16.2]), and post-resuscitation hypothermia (OR 30.0 [11.5-78.0]) were significantly associated with survival to hospital discharge. Conversely, pre-hospital epinephrine (OR 0.6 [0.4-0.9]) was associated negatively with survival. OHCA survival has improved in Singapore over the past 10 years. Improvement in response time, public AEDs and post-resuscitation hypothermia appear to have contributed to the increase in survival. Singapore's experience might suggest that developing EMS systems should focus on reducing times to basic life support, including bystander defibrillation and post-resuscitation care.

Research paper thumbnail of Prediction of adverse cardiac events in emergency department patients with chest pain using machine learning for variable selection

BMC Medical Informatics and Decision Making, 2014

Research paper thumbnail of Validation of a risk scoring model for prediction of acute cardiac complications in chest pain patients presenting to the Emergency Department

International Journal of Cardiology, 2014

Research paper thumbnail of Cost-Effectiveness of an Injury and Drowning Prevention Program in Bangladesh

Research paper thumbnail of Randomized Clinical Trial of Cutting Balloon Angioplasty versus High-Pressure Balloon Angioplasty in Hemodialysis Arteriovenous Fistula Stenoses Resistant to Conventional Balloon Angioplasty

Journal of Vascular and Interventional Radiology, 2014

Research paper thumbnail of Expert estimates of caregiver hours for older Singaporeans with dementia

Australasian Journal on Ageing, 2012

To obtain experts&amp... more To obtain experts' estimates of the number of non-medical care hours required by older Singaporeans at different stages of ageing-related dementia, with low or high behavioural features. Experts on dementia in Singapore attended one of two meetings where they provided estimates of the number of care hours required for individuals at mild, moderate and severe levels of dementia with either low or high behavioural features. The experts were shown the collated responses, given an opportunity to discuss as a group, and then polled again. The estimated mean care hours varied by dementia severity and the level of behavioural features. There was no interaction between dementia severity and behavioural features. Estimated care hours needed by individuals with dementia is independently influenced by severity of dementia and behavioural features. These estimates may be useful for policy-makers in projecting the impact of caregiving.

Research paper thumbnail of Ultrasound Imaging of Normal Displacement of the Extensor Carpi Ulnaris Tendon Within the Ulnar Groove in 12 Forearm–Wrist Positions

American Journal of Roentgenology, 2009

Instability of the extensor carpi ulnaris (ECU) tendon can be a difficult clinical diagnosis beca... more Instability of the extensor carpi ulnaris (ECU) tendon can be a difficult clinical diagnosis because of normal changes in tendon position during wrist motion. Our goal was to determine the normal variation of ECU tendon displacement in 12 forearm-wrist positions. Ultrasound imaging of the ECU tendons of 40 symptom-free wrists of healthy volunteers (13 women, seven men; mean age, 22.3 years; range, 20-25 years) was performed. Each ECU tendon was examined in 12 positions: four wrist positions (ulnar deviation, radial deviation, flexion, and extension) in each of three forearm positions (pronation, supination, and neutral). ECU tendon displacement in the right hand was not significantly different from that in the left, and displacement in men did not differ significantly from that in women. There was a small but significant difference between displacement in the dominant and that in the nondominant hand (p < 0.02). Mean ECU tendon displacement was greatest in the supinated forearm position (p < 0.001) followed by the neutral position (p < 0.001) and was least in the pronated position (p < 0.001). Both ulnar deviation (p < 0.001) and flexion (p < 0.002) were associated with greater ECU tendon displacement than were radial deviation (p…

Research paper thumbnail of Clinical and MRI Findings Associated with False-Positive Knee MR Diagnoses of Medial Meniscal Tears

American Journal of Roentgenology, 2008

The objective of our study was to determine if false-positive MR diagnoses of a medial meniscal t... more The objective of our study was to determine if false-positive MR diagnoses of a medial meniscal tear are more common with specific clinical variables, tear type or location, or MRI findings of a longitudinal tear. We reviewed the records of 559 patients who underwent knee MR examinations and arthroscopy. We compared the positive predictive values (PPVs) of an MR diagnosis of a medial meniscal tear for differences in tear location or type, delay between knee injury and MRI, delay between MRI and arthroscopy, and the presence of an anterior cruciate ligament (ACL) tear. We also retrospectively reviewed the MR examinations of 50 longitudinal tears to compare the PPVs of various MRI findings of a longitudinal tear. There was no association between either the delay between injury and MRI or the delay between MRI and arthroscopy and false-positive diagnoses. The PPV of 64% (32/50) for longitudinal tears was lower than the values of 83% (15/18) to 100% (116/116) for other types of medial meniscal tears. False-positive diagnoses of medial meniscal tears were more common in patients who had a prior episode of acute trauma (p = 0.004) or an ACL tear (p < 0.0001). Review of longitudinal tears revealed a decreased PPV when MRI showed signal contacting only the superior surface (p = 0.016) or when MRI showed signal contacting the surface at the meniscocapsular junction (p = 0.004). Four of the 18 menisci with a false-positive diagnosis of a longitudinal tear had a healed ACL tear noted at arthroscopy. False-positive MR diagnoses of medial meniscal tears are more common for longitudinal tears than other tear types and are also more common with MR abnormalities at either the superior surface or the meniscocapsular junction. Spontaneous healing of longitudinal tears accounts for some false-positive MR diagnoses.

Research paper thumbnail of Development of a Score and Probability Estimate for Detecting Angle Closure Based on Anterior Segment Optical Coherence Tomography

American Journal of Ophthalmology, 2014

To develop a score along with an estimated probability of disease for detecting angle closure bas... more To develop a score along with an estimated probability of disease for detecting angle closure based on anterior segment optical coherence tomography (AS OCT) imaging. Cross-sectional study. A total of 2047 subjects 50 years of age and older were recruited from a community polyclinic in Singapore. All subjects underwent standardized ocular examination including gonioscopy and imaging by AS OCT (Carl Zeiss Meditec). Customized software (Zhongshan Angle Assessment Program) was used to measure AS OCT parameters. Complete data were available for 1368 subjects. Data from the right eyes were used for analysis. A stepwise logistic regression model with Akaike information criterion was used to generate a score that then was converted to an estimated probability of the presence of gonioscopic angle closure, defined as the inability to visualize the posterior trabecular meshwork for at least 180 degrees on nonindentation gonioscopy. Of the 1368 subjects, 295 (21.6%) had gonioscopic angle closure. The angle closure score was calculated from the shifted linear combination of the AS OCT parameters. The score can be converted to an estimated probability of having angle closure using the relationship: estimated probability = e(score)/(1 + e(score)), where e is the natural exponential. The score performed well in a second independent sample of 178 angle-closure subjects and 301 normal controls, with an area under the receiver operating characteristic curve of 0.94. A score derived from a single AS OCT image, coupled with an estimated probability, provides an objective platform for detection of angle closure.

Research paper thumbnail of Risk stratification for prediction of adverse coronary events in emergency department chest pain patients with a machine learning score compared with the TIMI score

International Journal of Cardiology, 2014