Does irritable bowel syndrome increase the risk of interstitial cystitis/bladder pain syndrome? A cohort study of long term follow-up.

INTRODUCTION AND HYPOTHESIS: Interstitial cystitis/bladder pain syndrome (IC/BPS) and irritable bowel syndrome (IBS) often occur concomitantly without an obvious reason. It is important to determine the relationship between these related diseases. We aimed to determine whether IBS increase the risk of IC/BPS. METHODS: We identified newly diagnosed IBS patients between 2002 and 2013 from a nationwide database as the IBS cohort. Subjects diagnosed with IC/BPS before IBS were excluded. Cox's regression analysis with a hazard ratio (HR) of IC/BPS between IBS and the non-IBS cohort was applied to unmatched and matched (16 confounders of propensity scores) models. The time from diagnosis of IBS to IC/BPS was also calculated. RESULTS: In the unmatched group, which included 100,124 IBS (55% female) and 874,048 non-IBS patients, the IC/BPS adjusted HR was 1.292 (95% confidence interval [CI], 1.131-1.476;p < 0.0001) in the IBS cohort compared with the non-IBS cohort. In the matched group, there were 85,359 patients in each cohort, and the IC/BPS HR was 1.599 (95% CI, 1.344-1.903; p < 0.0001). The average numbers of years until the development of IC/BPS in the IBS cohort and non-IBS cohort were 4.60 ± 2.58 (n = 253) and 5.99 ± 3.49 (n = 295) years, respectively. CONCLUSIONS: IBS was shown to increase the risk of IC/BPS in this 12-year cohort study. The time from the diagnosis of IBS to IC/BPS was 5.35 ± 3.18 years. A common pathophysiology of IBS and IC/BPS is possible. Clinicians should be mindful of the association and promote collaborative care of these two elusive diseases.

Will cesarean section increase the risk of interstitial cystitis/painful bladder syndrome?

AIMS: A high number of patients with interstitial cystitis/painful bladder syndrome (IC/PBS) have a history of pelvic surgeries, and cesarean section is one of the most common pelvic surgeries in women. This study aimed to investigate if cesarean section increases the risk of IC/PBS. METHODS: Women who exclusively gave birth through cesarean section or vaginal delivery were identified from a nationwide database between 2002 and 2013. All were followed up during the study period to detect the event of IC/PBS. The IC/PBS hazard ratio (HR) in the cesarean cohort was compared with the vaginal delivery cohort with and without matching for confounding factors. RESULTS: The unmatched group included 22 158 cesarean deliveries and 40 214 vaginal deliveries. The IC/PBS HR in the cesarean cohort compared with that in the vaginal delivery cohort was 1.370 (95% confidence interval [CI], 0.903-2.079; P = 0.139). In the matched group, 8368 women were matched in each cesarean and vaginal delivery cohort using propensity scores for age and comorbidities. The IC/PBS HR was 0.725 (95%CI, 0.358-1.471; P = 0.373). Both HRs in these two groups were not significantly different. The incidence density of IC/PBS in delivered women, non-delivery women, and the general female population were not significantly different either (0.310, 0.255, and 0.292 per 1000 person-years, respectively; P = 0.549). CONCLUSIONS: The risk of IC/PBS was not different between cesarean and vaginal delivery after controlling the confounding factors in this cohort study. Cesarean section has no causal effect on IC/BPS. Furthermore, delivery was not a risk factor for IC/PBS.

Somatic symptoms are sensitive in predicting interstitial cystitis/bladder pain syndrome.

Objectives Somatic symptoms are somatic complaints accompanied by disproportionate thoughts, feelings, and behaviors related to such symptoms. The study investigated five International Classification of Diseases, Ninth Revision, Clinical Modification diagnoses hallmarked by somatic symptoms. The study hypothesized an increased risk of interstitial cystitis/bladder pain syndrome in patients with somatic symptoms. Methods The raw data were obtained from a nationwide health insurance reimbursement database over a 12-year period from 2002 to 2013. The study followed a somatic symptoms cohort ( n = 34,393) and non-somatic symptoms cohort ( n = 637,999) for interstitial cystitis/bladder pain syndrome. Both cohorts were stratified into three subgroups based on propensity scores calculated by sex, age, and 17 comorbidities of interstitial cystitis/bladder pain syndrome. Results The incidence density of interstitial cystitis/bladder pain syndrome between the somatic symptoms cohort and non-somatic symptoms cohort was significantly different in the three subgroups (relative ratio [95% confidence interval], 2.14 [1.01, 4.53], 1.52 [1.47, 1.57], and 1.59 [1.28, 1.98], respectively). The adjusted hazard ratio for interstitial cystitis/bladder pain syndrome was significantly greater in the female-dominant and older age subgroups-subgroup 2 and subgroup 3 (adjusted hazard ratios, 1.47 [1.07, 2.01] and 1.72 [1.38, 2.16], respectively). Conclusion The longitudinal investigation identified a subsequent risk of interstitial cystitis/bladder pain syndrome in patients with somatic symptoms. Somatic symptoms might be linked to biological pathways that might increase the risk of interstitial cystitis/bladder pain syndrome, much like more traditional psychosocial factors.

A cohort study of interstitial cystitis/bladder pain syndrome and hysterectomy.

INTRODUCTION AND HYPOTHESIS: Symptoms of interstitial cystitis/bladder pain syndrome (IC/BPS) are often confused with uterine conditions. Gynecologists may therefore recommend hysterectomy which was inappropriate for these patients. This study investigated whether IC/BPS increases the risk of hysterectomy in a large nationwide retrospective cohort study. METHODS: From the Longitudinal Health Insurance Database 2010 (LHID2010) in Taiwan, we identified women diagnosed with IC/BPS between 2002 and 2013. Those with a history of hysterectomy before IC/BPS diagnosis were excluded. All women were stratified into three subgroups (younger, middle, older age) based on the propensity scores of 15 confounding factors, including age and comorbidities. All were followed until the end of 2013 to detect the event of hysterectomy. The hazard ratio (HR) of hysterectomy in the IC/BPS cohort was compared with the non-IC/BPS cohort among the three subgroups by Cox regression after adjusting for confounding factors. RESULTS: In addition to the representative middle age, subgroup 2 had similar rates of comorbidities as the general population. The study was both externally and internally valid. The risk of hysterectomy in the IC/BPS cohort (n = 536) was significantly higher than in the non-IC/BPS cohort (n = 103846) in subgroup 2 (HR = 1.701, 95 % CI 1.056-2.740). The mean time to hysterectomy after diagnosis of IC/BPS was 2.97 years. CONCLUSIONS: In this nationwide study, we found that IC/BPS has a causal impact on hysterectomy in the middle-age subgroup in LHID 2010. The possibility of a woman having IC/BPS should be evaluated prior to hysterectomy to avoid inappropriate surgery.

Validation of overnight oximetry to diagnose patients with moderate to severe obstructive sleep apnea.

BACKGROUND: Polysomnography (PSG) is treated as the gold standard for diagnosing obstructive sleep apnea (OSA). However, it is labor-intensive, time-consuming, and expensive. This study evaluates validity of overnight pulse oximetry as a diagnostic tool for moderate to severe OSA patients. METHODS: A total of 699 patients with possible OSA were recruited for overnight oximetry and PSG examination at the Sleep Center of a University Hospital from Jan. 2004 to Dec. 2005. By excluding 23 patients with poor oximetry recording, poor EEG signals, or respiratory artifacts resulting in a total recording time less than 3 hours; 12 patients with total sleeping time (TST) less than 1 hour, possibly because of insomnia; and 48 patients whose ages less than 20 or more than 85 years old, data of 616 patients were used for further study. By further considering 76 patients with TST < 4 h, a group of 540 patients with TST ≥ 4 h was used to study the effect of insufficient sleeping time. Alice 4 PSG recorder (Respironics Inc., USA) was used to monitor patients with suspected OSA and to record their PSG data. After statistical analysis and feature selection, models built based on support vector machine (SVM) were then used to diagnose moderate and moderate to severe OSA patients with a threshold of AHI = 30 and AHI = 15, respectively. RESULTS: The SVM models designed based on the oxyhemoglobin desaturation index (ODI) derived from oximetry measurements provided an accuracy of 90.42-90.55%, a sensitivity of 89.36-89.87%, a specificity of 91.08-93.05%, and an area under ROC curve (AUC) of 0.953-0.957 for the diagnosis of severe OSA patients; as well as achieved an accuracy of 87.33-87.77%, a sensitivity of 87.71-88.53%, a specificity of 86.38-86.56%, and an AUC of 0.921-0.924 for the diagnosis of moderate to severe OSA patients. The predictive outcome of ODI to diagnose severe OSA patients is better than to diagnose moderate to severe OSA patients. CONCLUSIONS: Overnight pulse oximetry provides satisfactory diagnostic performance in detecting severe OSA patients. Home-styled oximetry may be a tool for severe OSA diagnosis.

DBCP: a web server for disulfide bonding connectivity pattern prediction without the prior knowledge of the bonding state of cysteines.

The proper prediction of the location of disulfide bridges is efficient in helping to solve the protein folding problem. Most of the previous works on the prediction of disulfide connectivity pattern use the prior knowledge of the bonding state of cysteines. The DBCP web server provides prediction of disulfide bonding connectivity pattern without the prior knowledge of the bonding state of cysteines. The method used in this server improves the accuracy of disulfide connectivity pattern prediction (Q(p)) over the previous studies reported in the literature. This DBCP server can be accessed at http://120.107.8.16/dbcp or http://140.120.14.136/dbcp.

Design of a Clinical Decision Support System for Predicting Erectile Dysfunction in Men Using NHIRD Dataset.

Erectile dysfunction (ED) affects millions of men worldwide. Men with ED generally complain failure to attain or maintain an adequate erection during sexual activity. The prevalence of ED is strongly correlated with age, affecting about 40% of men at age 40 and nearly 70% at age 70. A variety of chronic diseases, including diabetes, ischemic heart disease, congestive heart failure, hypertension, depression, chronic renal failure, obstructive sleep apnea, prostate disease, gout, and sleep disorder, were reported to be associated with ED. In this study, data retrieved from a subset of the National Health Insurance Research Database of Taiwan were used for designing the clinical decision support system (CDSS) for predicting ED incidences in men. The positive cases were male patients aged 20-65 who were diagnosed with ED between January 2000 and December 2010 confirmed by at least three outpatient visits or at least one inpatient visit, while the negative cases were randomly selected from the database without a history of ED and were frequency (1:1), age, and index year matched with the ED patients. Data of a total of 2832 ED patients and 2832 non-ED patients, each consisting of 41 features including index age, 10 comorbidities, and 30 other comorbidity-related variables, were retrieved for designing the predictive models. Integrated genetic algorithm and support vector machine was adopted to design the CDSSs with two experiments of independent training and testing (ITT) conducted to verify their effectiveness. In the 1st ITT experiment, data extracted from January 2000 till December 2005 (61.51%, 1742 positive cases and 1742 negative cases) were used for training and validating and the data retrieved from January 2006 till December 2010 were used for testing (38.49%), whereas in the 2nd ITT experiment, data in the training set (77.78%) were extracted from January 2000 till Deceber 2007 and those in the testing set (22.22%) were retrieved afterward. Tenfold cross validation and three different objective functions were adopted for obtaining the optimal models with best predictive performance in the training phase. The testing results show that the CDSSs achieved a predictive performance with accuracy, sensitivity, specificity, g-mean, and area under ROC curve of 74.72%-76.65%, 72.33%-83.76%, 69.54%-77.10%, 0.7468-0.7632, and 0.766-0.817, respectively. In conclusion, the CDSSs designed based on cost-sensitive objective functions as well as salient comorbidity-related features achieve satisfactory predictive performance for predicting ED incidences.

Design of a Clinical Decision Support System for Fracture Prediction Using Imbalanced Dataset.

More than 1 billion people suffer from chronic respiratory diseases worldwide, accounting for more than 4 million deaths annually. Inhaled corticosteroid is a popular medication for treating chronic respiratory diseases. Its side effects include decreased bone mineral density and osteoporosis. The aims of this study are to investigate the association of inhaled corticosteroids and fracture and to design a clinical support system for fracture prediction. The data of patients aged 20 years and older, who had visited healthcare centers and been prescribed with inhaled corticosteroids within 2002-2010, were retrieved from the National Health Insurance Research Database (NHIRD). After excluding patients diagnosed with hip fracture or vertebrate fractures before using inhaled corticosteroid, a total of 11645 patients receiving inhaled corticosteroid therapy were included for this study. Among them, 1134 (9.7%) were diagnosed with hip fracture or vertebrate fracture. The statistical results showed that demographic information, chronic respiratory diseases and comorbidities, and corticosteroid-related variables (cumulative dose, mean exposed daily dose, follow-up duration, and exposed duration) were significantly different between fracture and nonfracture patients. The clinical decision support systems (CDSSs) were designed with integrated genetic algorithm (GA) and support vector machine (SVM) by training and validating the models with balanced training sets obtained by random and cluster-based undersampling methods and testing with the imbalanced NHIRD dataset. Two different objective functions were adopted for obtaining optimal models with best predictive performance. The predictive performance of the CDSSs exhibits a sensitivity of 69.84-77.00% and an AUC of 0.7495-0.7590. It was concluded that long-term use of inhaled corticosteroids may induce osteoporosis and exhibit higher incidence of hip or vertebrate fractures. The accumulated dose of ICS and OCS therapies should be continuously monitored, especially for patients with older age and women after menopause, to prevent from exceeding the maximum dosage.

Sex Differences in the Risk of Developing Acute Coronary Syndrome in Patients With Sleep Disorders: A Population-Based Cohort Study.

Studies that focus on the relationship between sex and the risk of acute coronary syndrome (ACS) are scant. The current study investigated the effects of sex differences in the risk of developing ACS in patients with sleep disorders (SDs). This longitudinal population-based cohort study evaluated the incidence and risk of ACS development in 40,232 men and 65,519 women newly diagnosed with SDs between 2002 and 2008 from the Longitudinal Health Insurance Database. The follow-up period began from the entry date and ended on the date of an ACS event or December 31, 2010. Univariable and multivariable Cox proportional hazard regression models were conducted to estimate the sex differences in the risk of ACS. Men with SDs exhibited an increased incidence of ACS compared with women with SDs in all age- and comorbidity-specific subgroups. After covariates were adjusted, the men with SDs exhibited a 1.48-fold adjusted hazard ratio (aHR) of ACS compared with the women with SDs (95% confidence interval [CI] = 1.36-1.60). After age group stratification, the men with SDs in the young adult group exhibited the highest risk of subsequent ACS development compared with the women with SDs (aHR = 2.07, 95% CI = 1.69-2.55), followed by those in middle-aged adults (aHR = 1.52, 95% CI = 1.32-1.76) and older adults groups (aHR = 1.24, 95% CI = 1.11-1.39). This study determined that men with SDs, particularly young men, are at a higher risk of subsequent ACS development compared with women with SDs.

Somatoform disorder as a predictor of interstitial cystitis/bladder pain syndrome: Evidence from a nested case-control study and a retrospective cohort study.

Interstitial cystitis/bladder pain syndrome (IC/BPS) has several well-known comorbid psychiatric manifestations, including insomnia, anxiety, and depression. We hypothesized that somatoform disorder, which is a psychosomatic disease, can be used as a sensitive psychiatric phenotype of IC/BPS. We investigated whether somatoform disorder increases the risk of IC/BPS.A nested case-control study and a retrospective cohort study were followed up over a 12-year period (2002-2013) in the Taiwan Health Insurance Reimbursement Database. In the nested case-control study, 1612 patients with IC/BPS were matched in a 1:2 ratio to 3224 controls based on propensity scores. The odds ratio for somatoform disorder was calculated using conditional logistic regression analysis. In the retrospective cohort study, 1436 patients with somatoform disorder were matched in a 1:2 ratio to 2872 patients with nonsomatoform disorder based on propensity scores. Cox regression analysis was used to estimate the hazard ratio associated with the development of IC/BPS in patients with somatoform disorder, and the cumulative survival probability was tested using the Kaplan-Meier analysis.We found that the odds ratio for somatoform disorder was 2.46 (95% confidence interval [CI], 1.05-5.76). Although the average time until IC/BPS development in the control subjects was 11.5 ±â€Š1.3 years, this interval was shorter in patients with somatoform disorder (6.3 ±â€Š3.6 years). The hazard ratio for developing IC/BPS was 2.50 (95% CI 1.23-5.58); the adjusted hazard ratio was 2.26 (95% CI 1.002-5.007). The patients and controls also differed significantly in their cumulative survival probability for IC/BPS (log rank P < .05).Evidence from the nested case-control study and retrospective cohort study consistently indicated that somatoform disorder increases the risk for IC/BPS. Our study suggests that somatoform disorder can be used as a sensitive psychiatric phenotype to predict IC/BPS. Any past history of somatoform disorder should be documented while examining patients with IC/BPS.

Bronchiectasis and increased risk of ischemic stroke: a nationwide population-based cohort study.

BACKGROUND: Bronchiectasis is characterized by permanent dilatation of the bronchial tree caused by recurrent airway infection and inflammation. The association of atherosclerosis and inflammation is well established. However, studies on the relationship between bronchiectasis and stroke are scant. OBJECTIVE: We conducted a population-based cohort study to investigate the incidence and risk of ischemic stroke in patients with bronchiectasis. METHODS: Data of 1,295 patients newly diagnosed as bronchiectasis between 2000 and 2008 were retrieved from the Taiwan National Health Insurance Research Database. A total of 6,475 controls without bronchiectasis at a ratio of 5:1 were randomly selected from the general population based on frequency-matched age and sex to the patients. All participants were followed up to the date of ischemic stroke development, censoring, or the end of 2010. The Cox proportional hazard model was used to identify the risk of ischemic stroke in patients with bronchiectasis compared with those without bronchiectasis. RESULTS: The patients with bronchiectasis exhibited a higher incidence rate of ischemic stroke (9.18 vs 4.66 per 1,000 person-years) than the patients without bronchiectasis, with an adjusted hazard ratio of 1.74 (95% confidence interval =1.28-2.35). The patients with bronchiectasis and any comorbidities exhibited a 2.66-fold adjusted hazard ratio of ischemic stroke compared with those with neither bronchiectasis nor comorbidity (95% confidence interval =1.85-3.84). The patients with bronchiectasis carried a dose response of ischemic stroke according to the number of emergency visits and hospitalizations per year. CONCLUSION: This study indicated that bronchiectasis is an independent risk factor of ischemic stroke.

The Incidence and Risk of Herpes Zoster in Patients With Sleep Disorders: A Population-Based Cohort Study.

Lack of sleep can compromise the immune system, which may reactivate latent varicella-zoster virus. Studies on sleep disorders and the risk of herpes zoster (HZ) are scant.We conducted a population-based cohort study to evaluate the risk of HZ in patients with sleep disorders and potential risk factors for HZ development. We identified patients with sleep disorders without apnea from 2002 to 2005 by using the Taiwan Longitudinal Health Insurance Database. The patients without sleep disorders were randomly selected and frequency matched with patients with sleep disorders according to age, sex, and index year. We estimated the follow-up time in person-years for the patients from the entry date until HZ diagnosis, loss to follow-up, or the end of 2010. We used Cox proportional hazards regression models and a sensitivity analysis to estimate the risk of HZ while controlling for demographic characteristics and comorbidities. A total of 131,001 study participants (follow-up, 948,177 person-years; mean age, 51.2 ±â€Š16.5 years; 62.2% women) were included in the study. Patients with sleep disorders exhibited a higher incidence of HZ compared with a comparison cohort when stratified by age, sex, and comorbidities. After adjustment for covariates, the sleep disorder cohort exhibited a 1.23-fold greater risk of HZ compared with the comparison cohort (95% confidence interval [CI] = 1.17-1.30). The incidence of HZ increased with age. Adults ages 65 years and older exhibited a 6.11-fold greater risk of HZ development compared with their younger counterparts (95% CI = 5.34-7.00). Cancers and autoimmune diseases were independent risk factors of HZ development. The patients with sleep disorders may carry an increased risk of developing HZ.

Risks of acute coronary syndrome in patients with osteoarthritis: a nationwide population-based cohort study.

Recent studies have reported that osteoarthritis (OA) is related to inflammation and atherosclerosis. Studies on the relationship between OA and acute coronary syndrome (ACS) are scant. We evaluated the risk of ACS in OA patients of an Asian population. This longitudinal, population-based cohort study investigated the incidence and risk of ACS in 46,042 patients with newly diagnosed OA and 46,042 controls selected randomly from the general population and frequency matched according to age, sex, and entry year (2002-2003). The follow-up period ranged from the entry date until the date of an ACS event, loss to follow-up, or the end of 2010. We employed Cox proportional hazard models to estimate the effects of OA on the risk of ACS. The OA patients showed a 15 % higher risk of ACS than did the controls after adjustment for covariates (adjusted hazard ratio [aHR] = 1.15, 95 % confidence interval [CI] = 1.08-1.23). The risk of ACS in the OA patients was the greatest in young adults (aHR = 2.0, 95 % CI = 1.44-2.78), followed by middle-aged (aHR = 1.15, 95 % CI = 1.01-1.31) and older adults (aHR = 1.11, 95 % CI = 1.03-1.20). The risk of ACS was 1.96-fold in young adults with mild to moderate OA and 3.51-fold in young adults with severe OA compared with their counterparts without OA. OA carries an increased risk of ACS, particularly in young adults with severe OA. Clinicians should employ proactive strategies for preventing ACS occurrence in these patients.

Gout and a Subsequent Increased Risk of Erectile Dysfunction in Men Aged 64 and Under: A Nationwide Cohort Study in Taiwan.

OBJECTIVE: Few studies have examined the relationship between gout and erectile dysfunction (ED). We investigated whether patients with gout exhibited an increased risk of ED. METHODS: This longitudinal nationwide cohort study investigated the incidence and risk of ED in 19,368 men with gout who were newly diagnosed between January 2002 and December 2008. A total of 77,472 controls without gout were randomly selected from the general population and frequency-matched according to age and sex. The patients were followed up from the date on which they were included in the study cohort to the date of an ED event, censoring, or December 31, 2010. We conducted the Cox proportional hazard model to estimate the effects of gout on ED risk including age and comorbidities. RESULTS: The gout cohort exhibited a 1.21-fold adjusted HR of subsequent ED development compared with the non-gout cohort (95% CI 1.03-1.44). The incidence of ED increased with age in both cohorts and was higher among the patients in the gout cohort than among those in the non-gout cohort. Compared to the patients without gout and comorbidities, the patients with both gout and any type of comorbidity exhibited a 2.04-fold risk of developing ED (95% CI 1.63-2.57). Further, the patients with gout who had numerous comorbidities exhibited the dose-response effect in developing ED. CONCLUSION: This nationwide cohort study revealed that ED risk is significantly higher in patients with gout than in the general population.

Semi-automatic segmentation and classification of Pap smear cells.

Cytologic screening has been widely used for detecting the cervical cancers. In this study, a semiautomatic PC-based cellular image analysis system was developed for segmenting nuclear and cytoplasmic contours and for computing morphometric and textual features to train support vector machine (SVM) classifiers to classify four different types of cells and to discriminate dysplastic from normal cells. A software program incorporating function, including image reviewing and standardized denomination of file names, was also designed to facilitate and standardize the workflow of cell analyses. Two experiments were conducted to verify the classification performance. The cross-validation results of the first experiment showed that average accuracies of 97.16% and 98.83%, respectively, for differentiating four different types of cells and in discriminating dysplastic from normal cells have been achieved using salient features (8 for four-cluster and 7 for two-cluster classifiers) selected with SVM recursive feature addition. In the second experiment, 70% (837) of the cell images were used for training and 30% (361) for testing, achieving an accuracy of 96.12% and 98.61% for four-cluster and two-cluster classifiers, respectively. The proposed system provides a feasible and effective tool in evaluating cytologic specimens.

Disulfide connectivity prediction based on structural information without a prior knowledge of the bonding state of cysteines.

Previous studies predicted the disulfide bonding patterns of cysteines using a prior knowledge of their bonding states. In this study, we propose a method that is based on the ensemble support vector machine (SVM), with the structural features of cysteines extracted without any prior knowledge of their bonding states. This method is useful for improving the predictive performance of disulfide bonding patterns. For comparison, the proposed method was tested with the same dataset SPX that was adopted in previous studies. The experimental results demonstrate that bridge classification and disulfide connectivity predictions achieve 96.5% and 89.2% accuracy, respectively, using the ensemble SVM model, which outperforms the traditional method (51.5% and 51.0%, respectively) and the model that is based on a single-kernel SVM classifier (94.6% and 84.4%, respectively). For protein chain and residue classifications, the sensitivity, specificity, and accuracy of ensemble and single-kernel SVM approaches are better than those of the traditional methods. The predictive performances of the ensemble SVM and single-kernel models are identical, indicating that the ensemble model can converge to the single-kernel model for some applications.

Application of rational power functions in analyses of saccadic velocity profiles.

The relationship between the product of peak velocity and duration (VmD) and saccadic amplitude is tightly correlated. The velocity profile of a saccade was referred as a triangular profile; whereas the saccadic amplitude is proportional to VmD. From our observation and derivation, in addition to the triangular profile, the rational power function can also be applied to explain the linear relationship between the saccadic amplitude and VmD. In this study, rational power functions were used for the analyses of saccadic dynamics. The results show that the rational power functions were fitted very well to the velocity profiles for three different amplitudes, i.e. 10deg, 20deg, and 30deg, with correlation coefficients are all greater than 0.99. Significant differences in shape parameters between experimental and simulated profiles were also observed. Additionally, we have found that the minimum variance model proposed based on the minimization of variance of post-saccadic eye position cannot simulate velocity profiles matched with the experimental results. In conclusion, rational power functions are efficient in describing the saccadic velocity profiles. The shape parameters are also efficient for describing the dynamics of saccadic velocity profiles.