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PubMed2005

Refill persistence with chronic medication assessed from a pharmacy database was influenced by method of calculation.

BACKGROUND AND OBJECTIVES: In literature, different methods of calculating persistence are used. In this study, the effect of using these different methods on persistence and the association of patients characteristics and persistence are assessed. METHODS: The PHARMO record linkage system was used to calculate persistence with antihypertensive drugs for a cohort of 14,466 new users of antihypertensives. Three different types of methods were used to define the maximum gap allowed between two prescriptions that a patient may have to be defined as a continuous user, one based on a defined number of days (varying from 9-365 days), the second based on the duration of the last prescription (varying from 0.1-4 times the duration), the third based on a combination of both methods, whichever leads to the lowest number of days. RESULTS: Refill persistence varied between 19.7-86.4% (method 1), between 27.9-90.2% (method 2), and between 19.7-86.4% (method 3). Furthermore, patient characteristics associated with persistence differed between and within the three different methods. CONCLUSION: The method used and the variation within a method influenced both persistence and the association between patient characteristics and persistence. Results of persistence studies are highly influenced by the researchers' method of the maximum allowed treatment gap.

Adolescent↗
PubMed2006

How does intraspecific density regulation influence metapopulation synchrony and persistence?

Intraspecific density regulation influences the synchronization of local population dynamics through dispersal. Spatial synchrony in turn may jeopardize metapopulation persistence. Joining results from previous studies suggests that spatial synchrony is highest at moderate over-compensation and is low at compensating and at very strong over-compensating density regulation. We scrutinize this supposition of a unimodal relationship using a process-based metapopulation model with explicit local population dynamics. We extend the usually studied range of density regulation to under-compensation and analyse resulting metapopulation persistence. We find peaks of spatial synchrony not only at over-compensatory but also under-compensatory density regulation and show that effects of local density compensation on synchrony follow a bimodal rather than unimodal relationship. Persistence of metapopulations however, shows a unimodal relationship with a broad plateau of high persistence from compensatory to over-compensatory density regulation. This range of high persistence comprises both levels of low and high spatial synchrony. Thus, not synchrony alone jeopardizes metapopulation persistence, but only in interplay with high local extinction risk. The functional forms of the relations of density compensation with spatial synchrony and persistence are robust to increases in dispersal mortality, landscape dynamics, or density dependence of dispersal. However, with each of these increases the maxima of spatial synchrony and persistence shift to higher over-compensation and levels of synchrony are reduced. Overall, for over-compensation high landscape connectivity has negative effects while for under-compensation connectivity affects persistence positively. This emphasizes the importance of species life-history traits for management decisions with regard to landscape connectivity: while dispersal corridors are essential for species with under-compensatory density regulation, they may have detrimental effects for endangered species with over-compensation.

Animals↗
PubMed2001

Myocardial damage and left ventricular dysfunction in patients with and without persistent negative T waves after Q-wave anterior myocardial infarction.

Persistent T-wave inversions during the chronic stage of Q-wave myocardial infarction (MI) indicate the presence of a transmural infarction with a fibrotic layer pathologically. The aim of the present study was to examine the relation between left ventricular (LV) damage and changes in polarity of the T waves from the acute to chronic phase in patients with Q-wave anterior wall MI. We studied 140 patients with persistent T-wave inversions in leads with Q waves (negative T-wave group) and 158 patients with positive T waves (positive T-wave group) at 12 months after anterior MI. In the positive T-wave group, the precordial T waves reverted from a negative to a positive morphology < 3 months after MI in 21 patients (3 M-positive T-wave subgroup), 3 to 6 months in 52 patients (6 M-positive T-wave subgroup), and 6 to 12 months in 75 patients (12 M-positive T-wave subgroup). Ten patients had persistent positive T waves without initial T-wave inversion (persistent positive T-wave group). Wall motion index and LV dimension were higher and the wall thickness for the infarct area and LV ejection fraction were lower in the negative T-wave than in the positive T-wave groups, except the persistent positive T-wave group in the chronic stage (p < 0.0001). Wall motion in the infarcted area improved over the course of 1 year in the 3 M-, 6 M-, and 12 M-positive T-wave subgroups (p < 0.0001), but not in the persistent positive T-wave group. Among the patients with T-wave inversions after admission, those who had persistent negative T waves after 12 months had worse LV function. In patients with initial T-wave inversion, earlier normalization of the precordial T waves was associated with greater improvement in LV function. Patients with persistent positive T waves without initial negative T waves had poorer recovery of LV function than patients with persistent negative T waves. We conclude that the presence of inverted T waves in leads with abnormal Q waves 12 months after MI and the time required for T-wave normalization can be used to assess the degree of LV dysfunction.

Aged↗
PubMed2002

Persistence of placenta previa according to gestational age at ultrasound detection.

OBJECTIVE: To evaluate gestational age at ultrasound detection of placenta previa as a predictor of previa persistence until delivery, and to estimate the effects of previa type, parity, and prior cesarean delivery on previa persistence. METHODS: This was a retrospective cohort study of pregnancies with placenta previa detected during transabdominal or endovaginal ultrasound examination. Previa was categorized as complete if the placenta completely covered the internal cervical os or incomplete if the inferior placental edge partially covered or reached the margin of the os. Gestational age was grouped into 4-week intervals from 15 to 36 weeks. The outcome was cesarean delivery for persistent previa. RESULTS: Previa was detected during 940 ultrasound examinations in 714 pregnancies. Of those with placenta previa at 15-19 weeks, 20-23 weeks, 24-27 weeks, 28-31 weeks, and 32-35 weeks, previa persisted until delivery in 12%, 34%, 49%, 62%, and 73%, respectively. At each interval, complete previa was more likely to persist than incomplete previa, all P <.001. Prior cesarean delivery was an independent risk factor for persistent previa among women diagnosed with previa in the second trimester, P <.05. However, parity was not an independent risk factor for persistence at any gestational age interval after adjusting for prior cesarean delivery. CONCLUSION: Gestational age at ultrasound detection of placenta previa may be used to predict likelihood of previa persistence. After midpregnancy, risk of persistence appears to be higher than previously reported. Type of placentation and prior cesarean delivery are important factors that modify the risk that previa will complicate delivery.

Cesarean Section↗
PubMed2001

Persistent ovarian follicles in dairy cows: a therapeutic approach.

Anestrus is common during the postpartum period in high-producing dairy cows. In a previous investigation, we were able to diagnose persistent follicles of 8 to 12 mm in anestrous cows. This report describes 2 consecutive studies. The objectives of the first were to 1) assess the association of persistent follicles with anestrus; and 2) evaluate 2 therapeutic treatments. In the second study, we compared the effectiveness of the best treatment established in Study 1 with the Ovsynch protocol. For Study 1, anestrous cows were considered to have a persistent follicle if it was possible to observe a single follicular structure > 8 mm in the absence of a corpus luteum or a cyst in 2 ultrasonographic examinations performed at an interval of 7 d. At diagnosis (Day 0), cows were assigned to 1 of 3 treatment groups. Cows in Group GnRH/PGF (n=17) were treated with 100 microg GnRH i.m., and 25 mg PGF2alpha i.m. on Day 14. Cows in Group PRID (n=18) were fitted with a progesterone releasing intravaginal device (PRID, containing 1.55 g of progesterone) for 9 d and were given 100 microg GnRH i.m. at the time of PRID insertion, and 25 mg PGF2alpha i.m. on Day 7. Cows in Group Control (n=18) received no treatment. The animals were inseminated at observed estrus and were monitored weekly by ultrasonography until AI or 5 weeks from diagnosis. Blood samples were also collected on a weekly basis for progesterone determination. The mean size of persistent follicles on Day 0 was 9.4 +/- 0.04 mm. Progesterone levels were < 0.2 ng/mL during the first 35 d in 16 of 18 Control cows. Cows in the PRID group showed a lower persistent follicle rate (16.7% < 70.6% < 88.9%; P < 0.0001; PRID vs GnRH/PGF vs Control, respectively); a higher estrus detection rate (83.3% > 29.4% > 11.1%; P < 0.0001) and a higher pregnancy rate (27.8% > 5.9% > 0%; P = 0.02). For the second study, 145 cows with persistent follicles were randomly assigned to 1 of 2 treatment groups: cows in Group Ovsynch (n=73) were treated with 100 microg GnRH i.m. on Day 0, 25 mg PGF2alpha i.m. on Day 7, and 100 microm GnRH i.m. 32 h later. Cows in this group were inseminated 16 to 20 h after the second GnRH dose (Ovsynch protocol). Cows in Group PRID (n=72) were treated as those in the PRID group of Study 1, and were inseminated 56 h after PRID removal. Cows in the PRID group showed a higher ovulation rate (84.8% > 8.2%: P < 0.0001); a higher pregnancy rate (34.2% > 4.1%; P < 0.0001) and lower follicular persistence rate (22.2% < 63%; P < 0.0001) than those in Ovsynch. Our results indicate that persistent follicles affect cyclic ovarian function in lactating dairy cows. Cows with persistent follicles can be successfully synchronized and time inseminated using progesterone, GnRH and PGF2alpha but show a limited response to treatment with GnRH plus PGF2alpha.

Anestrus↗
PubMed2002

Efficacy of budesonide in inhaled corticosteroid-naive patients and patients with mild persistent asthma.

BACKGROUND: Patients with mild intermittent or mild persistent asthma represent 70% of asthma sufferers. Inhaled corticosteroids (ICSs) are the mainstay of treatment for persistent asthma, although many of the early clinical studies of these drugs included only patients with moderate to severe asthma. OBJECTIVE: This article reviews the literature on the efficacy of budesonide in the treatment of mild persistent asthma, including newly diagnosed ICS-naive patients. METHODS: Published data were identified by a MEDLINE search of the English-language literature from 1992 to 2002 using the terms budesonide plus efficacy or safety, both with and without the termsfluticasone or beclomethasone. An AstraZeneca reference database was also used to identify publications from the same period. Controlled, randomized studies that included patients with mild persistent asthma and early-treatment intervention were selected for inclusion. RESULTS: Inhaled budesonide has been used for almost 20 years in the treatment and control of moderate to severe asthma. Studies involving patients with mild persistent asthma have demonstrated significant improvements in peak expiratory flow (PEF) rates (P < 0.01) and forced expiratory volume in I second (P < 0.016) values for adult, adolescent, and pediatric patients treated with budesonide compared with placebo. Budesonide therapy is effective when given once or twice daily via dry powder inhaler or nebulizer, even at a low starting dose (200 microg/d). No significant adverse events have been reported with budesonide within the dose range used to treat mild persistent asthma (200 to 400 microg/d). Significant improvements in PEF rates (P < 0.01) and significant reductions in the risk of exacerbations and the number of days with poorly controlled asthma have been reported for ICS-naive patients treated with budesonide compared with placebo (both P < 0.001). In the primary care setting, mild persistent asthma may be undertreated. Patients with mild persistent asthma benefit significantly from early treatment with budesonide (P < 0.05). CONCLUSIONS: Budesonide is effective and well tolerated in the treatment of mild persistent asthma in adults and children, including many patients whose primary care physicians do not think they require daily ICS treatment.

Administration, Inhalation↗
PubMed2001

A cross-national study of the course of persistent pain in primary care.

Data from the World Health Organization's study of psychological problems in general health care were used to examine the course of persistent pain syndromes among primary care patients. Across 15 sites in 14 countries, 3197 randomly selected primary care patients completed baseline and 12-month follow-up assessments of pain, other somatic symptoms, and anxiety and depressive disorders (the Composite International Diagnostic Interview), and an assessment of occupational role disability (the Social Disability Schedule). Of patients with a persistent pain condition at baseline, 49% had not recovered 12 months later. The probability of non-recovery varied significantly across study centers and was significantly associated with the number of pain sites at baseline. After adjustment for age, sex, and study center, baseline anxiety or depressive disorder did not predict non-recovery of persistent pain. Among those without a persistent pain disorder at baseline, the rate of onset was 8.8% with a significant variability in risk across centers. The baseline characteristics predicting the onset of persistent pain disorder were psychological disorder, poor self-rated health, and occupational role disability. A persistent pain disorder at baseline predicted the onset of a psychological disorder to the same degree that a baseline psychological disorder predicted the subsequent onset of persistent pain. Persistent pain conditions are common among primary care patients, and the probability of resolution over 12 months is approximately 50%. We found a strong and symmetrical relationship between persistent pain and psychological disorder. Impairment of daily activities appears to be a central component of that relationship.

Adult↗
PubMed1999

Difficulties generated by the small, persistently patent, arterial duct.

Over recent years, echo-Doppler cardiography has shown that a small, sometimes silent, arterial duct exists in more patients than previously recognized. To know the incidence of an arterial duct subsequent to therapy, we studied retrospectively our patients undergoing open-heart surgery and surgical or catheter closure. Three groups of patients were studied: those with patency of the duct subsequent to open heart surgery without any sign of patency before or during surgery, those with persistent duct after surgical ligation and those with persistent patency after attempted catheter occlusion with the Rashkind device. In the first group (of 431 children) four (0.9%) had persistence of this duct, of which three were silent. In the second group, patency persisted in four of 100 patients (4%), three being silent. In the last group there were five persisting shunts, three producing no murmur, in 30 patients (17%). We compared our results with those reported in the literature and conclude that echo-Doppler cardiography is needed to detect persistent shunting across a duct after therapy, since most of the residual ducts in this study were silent. This means that clinical findings alone cannot be relied upon, and careful echo-Doppler cardiography is essential. Also, the process of closure of a persistent duct by surgical ligation or transcatheter intervention is no guarantee of success. The risk of infective endocarditis is important in such persistent ducts and, at present, it is unknown either for a small, silent duct or in a persistent duct that remains open after attempted transcatheter closure, but now is in association with a foreign body.

Child↗
PubMed2002

EPR investigation of persistent radicals produced from the photolysis of dibenzyl ketones adsorbed on ZSM-5 zeolites.

Photolysis of ketones (1, 1-oMe, 2, 2-oMe, 3, and 4) adsorbed on ZSM-5 zeolites produces persistent carbon-centered radicals that can be readily observed by conventional steady-state EPR spectroscopy. The radicals are persistent for time periods of seconds to many hours depending on the supramolecular structure of the initial radical@zeolite complex and the diffusion and reaction dynamics of radicals produced by photolysis. The structures of the persistent radicals responsible for the observed EPR spectra are determined by a combination of alternate methods of generation of the same radical, by deuterium substitution, and by spectral simulation. A clear requirement for persistence is that the radicals produced by photolysis must either separate and diffuse from the external to the internal surface or be generated within the internal surface and separate and diffuse apart. The persistence of radicals located on the internal surface is the result of inhibition of radical-radical reactions. Radicals that are produced on the external surface and whose molecular structure prevents diffusion into the internal surface are transient because radical-radical reactions occur rapidly on the external surface. The reactions of the persistent radicals with oxygen and nitric oxide were directly studied in situ by EPR analysis. In the case of reaction with oxygen, persistent peroxy radicals are formed in high yield. The addition of nitric oxide scavenges persistent radicals and leads initially to a diamagnetic nitroso compound, which is transformed into a persistent nitroxide radical by further photolysis. The influence of variation of radical structure on transience/persistence is discussed and correlated with supramolecular structure and reactivity of the radicals and their parent ketones.

Journal Article↗
PubMed2005

Correlates of persistent thinness in black and white young women.

OBJECTIVE: To examine health and psychosocial correlates of persistent thinness in black and white young adult women. RESEARCH METHODS AND PROCEDURES: 1,830 females (n = 988 black, n = 842 white) who participated in the National Heart, Lung, and Blood Institute Growth and Health Study were asked to indicate their current body size from a series of nine pictograms (1, emaciated to 9, obese). Persistent thinness was defined as having at least seven non-missing measurement points between ages 9 to 18 with a body size rating of <4 at all points. Generalized linear models were used to examine whether persistently thin women differed from comparison women on cardiovascular disease risk factors measured at age 18.5 and psychosocial variables measured at age 21.5. Prospective associations between psychological measures in childhood and persistent thinness through the course of adolescence were also examined. RESULTS: In the sample, 145 women (7.9%) met criteria for persistent thinness and 1,685 women (92.1%) were classified as not persistently thin. Persistently thin women had a later age of menarche, fewer weight concerns, and healthier eating attitudes, were less likely to have had a child, came from higher socioeconomic backgrounds, and had significantly lower blood pressure and higher high-density lipoprotein-cholesterol than comparison women. Differences were not found on measures of depression or health services use. Girls with higher self-esteem in childhood were more likely to remain persistently thin throughout adolescence. DISCUSSION: Persistently thin women seem to be healthier on several indicators relative to comparison women, and race did not moderate these differences.

Adolescent↗
PubMed2004

Characteristics of persistent smoking among pregnant teenagers followed to young adulthood.

Pregnant teenagers (N=344) were interviewed during first and third trimesters (average age=16.2 years) and interviewed again as young adults (average age=23.0 years). Nearly 47% were smokers during the first trimester, 58% smoked during the third trimester, and 61% were smokers in their early adult years. Some 40% (n=137) continued smoking into young adulthood (persistent smokers); 7% quit. Average number of cigarettes per day was 10.0 among persistent smokers and 6.8 among quitters (p<.05). Nearly 20% started smoking by young adulthood (late-onset smokers). Persistent smokers and quitters were most similar to one another, and they differed from the late-onset smokers and persistent nonsmokers on demographic, psychological, and behavioral measures. These variables from the teenage years included White race, lower maternal education, lower school grades, more aggression and delinquency problems, and earlier and more peer use of substances. Characteristics from the adult years included White race; lower education; and more anxiety, hostility, and alcohol use. Multivariate analyses using discriminant function analyses showed that three characteristics from the teenage years discriminated across the three smoking groups (persistent, late-onset, quitters): White race, friends' smoking, and lower maternal education. The same analyses using the adult characteristics showed that White race and lower personal educational level discriminated the persistent smokers and quitters from the late-onset smokers. Lower gravidity discriminated the persistent smokers from the quitters. Characteristics of women who are at highest risk of persistent smoking can be identified in both the teenage years and the early adult years, and appropriate interventions can be targeted to those women at highest risk of persistent smoking.

Adolescent↗
PubMed2006

The persistence of anticardiolipin antibodies is associated with an increased risk of the presence of lupus anticoagulant and anti-beta2-glycoprotein I antibodies.

OBJECTIVE: We studied antiphospholipid antibodies (aPL) in blood samples from a cohort of individuals followed for thrombosis to determine whether the persistent presence of anticardiolipin antibodies (aCL) is associated with a greater likelihood of having lupus anticoagulant and/or anti-beta2-glycoprotein I antibodies (LA/abeta2GPI). METHODS: Blood samples from 353 individuals who had been tested for aCL on at least two occasions were tested for abeta2GPI and LA. Two groups were defined: aCL-persistent, who tested aCL-positive on at least two occasions, and aCL non-persistent, who tested aCL-positive on fewer than two occasions. Multivariate logistic regressions were performed using LA/abeta2GPI, LA and abeta2GPI as outcome variables and the percentage of aCL-positive tests as the predictor variable, adjusted for age, gender, family history of cardiovascular disease (CVD), systemic lupus erythematosus (SLE), smoking and number of venous (VT) and arterial thromboses (AT). RESULTS: Sixty-eight (19%) individuals were aCL persistent and 285 (81%) were aCL non-persistent. LA/abeta2GPI was found in 36 (53%) of the aCL persistent group and 38 (13%) of the aCL non-persistent group. The two groups were similar for age, gender and smoking. Family history of CVD, SLE, VT and AT were more frequent in the aCL persistent group. Multivariate analyses revealed that odds ratios for LA/abeta2GPI, LA and abeta2GPI were 1.34 [95% confidence interval (CI) = 1.22-1.47], 1.36 (95% CI = 1.24-1.50) and 1.47 (95% CI = 1.31-1.65) respectively for each 10% increase in aCL-positive tests vs 0% positive tests. CONCLUSION: Persistence of aCL positivity is associated with an increased risk of LA/abeta2GPI.

Adult↗
PubMed2001

Epidemiology of postshigellosis persistent diarrhea in young children.

BACKGROUND: Dysentery accounts for 20% of the 4.6 million diarrhea-associated deaths among children in developing countries, with the risk from death in dysenteric persistent diarrhea 10-fold higher than that in acute dysentery. Although Shigella accounts for the majority of dysenteric episodes, very little is known about the epidemiology of postshigellosis persistent diarrhea. METHODS: Rural Bangladeshi children younger than 5 years of age (n = 1,756) were followed for 1 month after exposure to sentinel cases of Shigella dysentery. The likelihood of an acute diarrheal episode becoming persistent was assessed. RESULTS: Diarrhea caused by Shigella was significantly associated with an increased risk of persistent diarrhea (age-adjusted relative risk, 1.83; 95% confidence interval, 1.19 to 2.81). Despite the use of nalidixic acid in dysenteric episodes, persistent diarrhea occurred in 23% of children with shigellosis. Infection by multiply antibiotic-resistant Shigella isolates (age-adjusted relative risk, 3.76; 95% confidence interval, 1.51 to 9.36) and occurrence of shigellosis during infancy were observed to be risk factors for initiation of Shigella diarrhea persistence. However, 88% of the persistent shigellosis episodes occurred in older children, 50% were associated with nondysenteric shigellosis and 79% were caused by Shigella species other than Shigella dysenteriae 1. CONCLUSIONS: These data demonstrate the importance of Shigella as a cause of persistent diarrhea and indicate that strategies to prevent postshigellosis persistent diarrhea must be broad-based, with a focus on older children as well as infants, management of nondysenteric as well as dysenteric disease and prevention of diarrhea caused by multiple Shigella species.

Bangladesh↗
PubMed2004

Klippel-Feil syndrome associated with persistent trigeminal artery.

STUDY DESIGN: In the present report, radiologic findings of the patient with the Klippel-Feil syndrome associated with persistent trigeminal artery are reviewed. In same case, there was also spina bifida occulta, cervical spondylosis, atlanto-occipital assimilation, bilateral cervical ribs, and lack of flow signal in the C4 segment of contralateral vertebral artery. The persistent trigeminal artery and Klippel-Feil syndrome can be seen together and with the other anomalies. It should be considered that they might be related with the insufficiency or dysfunction of the embryologic developmental process. OBJECTIVES: To draw attention to this rare presentation of Klippel-Feil syndrome associated with persistent trigeminal artery. SUMMARY OF BACKGROUND DATA: Klippel-Feil syndrome is a congenital spinal malformation characterized by the failure in segmentation of 2 or more cervical vertebrae. Although the anomaly is defined by its skeletal component, Klippel-Feil Syndrome may also be associated with developmental defects in many other organ systems including the inner ear, spinal cord, heart, and genitourinary tract. The primitive trigeminal, otic, hypoglossal, and proatlantal intersegmental arteries are persistent fetal anastomoses between the carotid and vertebrobasilar circulations. The authors report the association of a persistent trigeminal artery with the Klippel-Feil syndrome. METHODS: Radiologic findings of a case of Klippel-Feil syndrome associated with persistent trigeminal artery are described. RESULTS: There was vertebral fusion, spina bifida occulta, bilateral cervical ribs, atlanto-occipital assimilation, and cervical spondylosis. Magnetic resonance angiography showed the persistent trigeminal artery between the left internal carotid and basilar artery, but there was no sign of flow in the C4 segment of right vertebral artery. CONCLUSIONS: It should be kept in mind that a persistent trigeminal artery and Klippel-Feil syndrome can be seen together and with the other anomalies. Because of this reason, this type of case should prompt a search for the other related anomalies, and magnetic resonance angiography can be used as a noninvasive diagnostic technique in the persistent trigeminal artery determination.

Abnormalities, Multiple↗
PubMed2004

Persistence in nonequilibrium surface growth.

Persistence probabilities of the interface height in ( 1+1 ) - and ( 2+1 ) -dimensional atomistic, solid-on-solid, stochastic models of surface growth are studied using kinetic Monte Carlo simulations, with emphasis on models that belong to the molecular beam epitaxy (MBE) universality class. Both the initial transient and the long-time steady-state regimes are investigated. We show that for growth models in the MBE universality class, the nonlinearity of the underlying dynamical equation is clearly reflected in the difference between the measured values of the positive and negative persistence exponents in both transient and steady-state regimes. For the MBE universality class, the positive and negative persistence exponents in the steady-state are found to be theta(S)(+) =0.66+/-0.02 and theta(S)(-) =0.78+/-0.02, respectively, in ( 1+1 ) dimensions, and theta(S)(+) =0.76+/-0.02 and theta(S)(-) =0.85+/-0.02, respectively, in ( 2+1 ) dimensions. The noise reduction technique is applied on some of the ( 1+1 ) -dimensional models in order to obtain accurate values of the persistence exponents. We show analytically that a relation between the steady-state persistence exponent and the dynamic growth exponent, found earlier to be valid for linear models, should be satisfied by the smaller of the two steady-state persistence exponents in the nonlinear models. Our numerical results for the persistence exponents are consistent with this prediction. We also find that the steady-state persistence exponents can be obtained from simulations over times that are much shorter than that required for the interface to reach the steady state. The dependence of the persistence probability on the system size and the sampling time is shown to be described by a simple scaling form.

Journal Article↗
PubMed2005

Persistence and determinants of statin therapy among middle-aged patients for primary and secondary prevention.

AIMS: Statins have been shown to significantly reduce morbidity and mortality in patients with coronary artery disease (CAD), and also in patients with dyslipidaemia when statins are taken regularly. Middle-aged patients have the highest level of forecasting benefit and little is known about persistence rate of these therapies in a real-life setting. The objective was to evaluate the persistence rate of middle-aged patients initiating a statin therapy and its relation with several determinants for primary and secondary prevention. METHODS: A cohort was reconstructed using the RAMQ databases. All patients aged 50-64 years-old who received at least one statin prescription between 1 January, 1998 and 31 December, 2000 for a new intention of treatment for dyslipidaemia were included in the cohort and followed up until 30 June, 2001. The date of the first prescription of statin was defined as the index date. There were 4316 patients in the secondary prevention (CAD diagnosis) and 13,642 patients in primary prevention cohort. The cumulative persistence rate was estimated using Kaplan-Meier, and Cox regression models were used to estimate the hazard ratio of ceasing statins. RESULTS: We found that persistence with statins had fallen to 71% after 6 months of treatment, and had declined to 45% after 3 years in the secondary prevention cohort; the corresponding figures were 65% and 35% in the primary prevention cohort. Our results suggest that patients with dyslipidaemia in primary prevention compared with those in secondary prevention (HR: 1.18; 1.11-1.25) are less likely to be persistent. Patients with other cardiovascular risk factors such as age (HR: 0.99; 0.98-0.99), diabetes (HR: 0.84; 0.79-0.90), hypertension (HR: 0.76; 0.72-0.80) were most likely to be persistent with statins. We observed lower persistence in patients who have used the greatest number of pharmacies and prescribing physicians. CONCLUSION: This analysis indicates that barriers to persistence occur early in the therapeutic course. Overall persistence with statins is low, and particularly among patients with few other cardiovascular risk factors.

Cohort Studies↗
PubMed2005

Characteristics of intermittent and persistent allergic rhinitis: DREAMS study group.

BACKGROUND: In the Allergic Rhinitis and its Impact on Asthma (ARIA) classification, intermittent and persistent rhinitis were proposed to replace seasonal and perennial allergic rhinitis (AR). AIM: To better understand the ARIA classification of rhinitis. METHODS: A cross-sectional study was carried out in 591 patients consulting ENT or allergy specialists for AR and 502 control subjects. The diagnosis of AR was based on a score for allergic rhinitis (SFAR) > or =7. Patients were classified according to the four ARIA classes (mild intermittent, mild persistent, moderate/severe intermittent and moderate/severe persistent). Allergen sensitization (skin prick tests (SPTs) or specific IgE) and co-morbidities were examined according to the ARIA classes. RESULTS: Ten percent of patients had mild intermittent rhinitis, 14% mild persistent rhinitis, 17% moderate/severe intermittent rhinitis and 59% moderate/severe persistent rhinitis. Most patients with intermittent rhinitis had a pollen sensitivity, but 5% had a single house dust mite (HDM) sensitization. Over 50% of patients with persistent rhinitis were allergic to pollens or HDM. Asthma was present in 24% of rhinitis patients and in only 2% of the control population (P<0.0001). Patients with moderate/severe persistent rhinitis had the highest asthma prevalence (33%). DISCUSSION: Intermittent and persistent rhinitis are not synonymous of seasonal and perennial rhinitis. Most patients consulting specialists have severe rhinitis. Asthma prevalence increases with duration and severity of rhinitis supporting the ARIA major recommendation that patients with persistent rhinitis should be evaluated for asthma.

Adolescent↗
PubMed1999

Direct demonstration of persistent Na+ channel activity in dendritic processes of mammalian cortical neurones.

1. Single Na+ channel activity was recorded in patch-clamp, cell-attached experiments performed on dendritic processes of acutely isolated principal neurones from rat entorhinal-cortex layer II. The distances of the recording sites from the soma ranged from approximately 20 to approximately 100 microm. 2. Step depolarisations from holding potentials of -120 to -100 mV to test potentials of -60 to +10 mV elicited Na+ channel openings in all of the recorded patches (n = 16). 3. In 10 patches, besides transient Na+ channel openings clustered within the first few milliseconds of the depolarising pulses, prolonged and/or late Na+ channel openings were also regularly observed. This 'persistent' Na+ channel activity produced net inward, persistent currents in ensemble-average traces, and remained stable over the entire duration of the experiments ( approximately 9 to 30 min). 4. Two of these patches contained < or = 3 channels. In these cases, persistent Na+ channel openings could be attributed to the activity of one single channel. 5. The voltage dependence of persistent-current amplitude in ensemble-average traces closely resembled that of whole-cell, persistent Na+ current expressed by the same neurones, and displayed the same characteristic low threshold of activation. 6. Dendritic, persistent Na+ channel openings had relatively high single-channel conductance ( approximately 20 pS), similar to what is observed for somatic, persistent Na+ channels. 7. We conclude that a stable, persistent Na+ channel activity is expressed by proximal dendrites of entorhinal-cortex layer II principal neurones, and can contribute a significant low-threshold, persistent Na+ current to the dendritic processing of excitatory synaptic inputs.

Algorithms↗