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PubMed2003

Murine intestinal migrating motor complexes: longitudinal components.

Spontaneous migrating contractions have been described in the circular muscle of the isolated mouse colon and terminal ileum, however, spontaneous events equivalent to these have not been reported in the longitudinal muscle. The longitudinal muscle shortenings in the colon and ileum, which are of similar form, frequency and pharmacology to the circular muscle colonic and ileal migrating motor complexes (CMMCs and IMMCs), are recorded in the present study. The spontaneous ileal and colonic longitudinal muscle shortenings appear to be neurally organized as they are abolished by tetrodotoxin (1 micro mol L-1), hexamethonium (500 micro mol L-1) and morphine (1 micro mol L-1). Endogenously released nitric oxide slowed the frequency of spontaneous ileal and colonic longitudinal muscle shortenings and 5-hydroxytryptamine increased their frequency. Hyoscine (1 micro mol L-1) abolished longitudinal shortenings in the ileum and reduced the amplitude of longitudinal shortening by approximately 44% in the colon. Shortenings were effectively abolished by nifedipine (1 micro mol L-1). Surgical sectioning of the colon identified that each region of the colon contracted longitudinally in an independent fashion; the distal colon contracted to the greatest amplitude and lowest frequency. The longitudinal preparation is suitable to initially assess the actions of novel pharmacological agents on spontaneous, neurally coordinated, CMMCs and IMMCs in emptied isolated murine intestines.

Anesthetics, Local↗
PubMed2002

Quantification of regional left and right ventricular radial and longitudinal function in healthy children using ultrasound-based strain rate and strain imaging.

BACKGROUND: Noninvasive assessment of left (LV) and right (RV) ventricular function in children could benefit from a technique that would characterize local myocardial deformation. Color Doppler myocardial imaging (CDMI) allows the calculation of either local longitudinal or radial Strain Rate (SR) and Strain (epsilon). To determine the clinical feasibility and reproducibility of longitudinal and radial SR and epsilon, the following study was carried out. METHODS: CDMI data were obtained from 33 healthy children (4-16 years). To quantify regional longitudinal and radial function SR and epsilon data were obtained from apical and parasternal views respectively. From the extracted SR curves, peak values for systole, early diastole, and late diastole were calculated. From the extracted epsilon curves the systolic, early and late diastolic epsilon values were calculated. RESULTS: LV longitudinal deformation were homogeneous for LV basal, mid and apical segments (peak systolic SR: -1.9 +/- 0.7 s(-1), systolic epsilon -25% +/- 7%). Longitudinal SR and epsilon values were significantly higher and heterogeneous in the RV (compared with LV walls) and were maximal in the mid part of the RV free wall (peak systolic SR: -2.8 +/- 0.7 s(-1), systolic epsilon -45% +/- 13%). The RV inferior wall showed homogeneous but lower longitudinal SR and epsilon values. The LV systolic and diastolic SR and epsilon values were higher for deformation in the radial direction compared with the longitudinal direction (radial peak systolic SR: 3.7 +/- 0.9 s(-1), radial systolic epsilon 57% +/- 11%; P <.0001). The interobserver variability for radial systolic epsilon and SR was 10.3% and 13.1%, respectively. CONCLUSION: Ultrasound-based Strain SR/epsilon imaging is a practical, reproducible clinical technique, which allows the calculation of regional longitudinal and radial deformation from both LV and RV segments. The combination of regional SR/epsilon indices and the timing of specific systolic or diastolic regional events may offer a new noninvasive approach to quantifying regional myocardial function in congenital and acquired heart disease in children.

Adolescent↗
PubMed2001

Transmission of rectal electric waves: is it through circular or longitudinal smooth muscle layers or both?

The rectum possesses electric activity in the form of pacesetter (PPs) and action potentials (APs). In recent studies we suggested that the waves are not initiated by the extrarectal autonomic innervation but might be triggered by a 'rectosigmoid pacemaker' and are transmitted in the rectal wall through the rectal musculature and not the enteric nerve plexus. To investigate whether the rectal waves are transmitted through the circular or longitudinal muscle layer, the rectum of 18 mongrel dogs was exposed under anesthesia through an abdominal incision. Three electrodes were applied to the rectal wall (longitudinal muscle layer) and another 3 electrodes to the circular muscle; the latter was exposed by splitting apart the fibers of the longitudinal muscle. Rectal electric activity and pressure were recorded from the 6 electrodes before and after performing individual myotomy of the rectal longitudinal (9 dogs), circular (9 dogs), and then the whole muscle layers (18 dogs). The myotomy was performed proximal to and between the electrodes. Pacesetter (PPs) and action potentials (APs) were recorded from the 3 electrodes on the longitudinal muscle but no waves were registered from those on the circular muscle. After longitudinal muscle myotomy was performed between electrodes 1 and 2, PPs and APs were recorded from electrode 1 but not 2 and 3 and when performed proximally to electrode 1, no waves were registered. The rectal pressure increased concomitantly with occurrence of APs. Circular muscle myotomy effected no change in the rectal electric activity recorded from the 3 electrodes applied to the longitudinal muscle. In total muscle myotomy, the electric waves were recorded from the electrodes proximal but not distal to the myotomy. We propose that the motile activity of the rectal longitudinal muscle is initiated by the electric activity which appears to be triggered by the rectosigmoid pacemaker, while that of the circular muscle fibers is believed to be initiated by the stretch reflex induced by rectal distension. This concept is evidenced not only by the current findings but also by the histologic structure of the rectal musculature being of the unitary type of smooth muscles.

Action Potentials↗
PubMed2005

Treatment of compartment syndrome: transverse fasciotomy as an adjunct to longitudinal dermatofasciotomy: an in vitro study.

OBJECTIVE: This study describes a previously unpublished technique for compartment release that combines adjunctive transverse fasciotomies with a limited longitudinal dermatofasciotomy and compares its efficacy with a standard extensile longitudinal dermatofasciotomy. DESIGN: Limited 10-cm longitudinal dermatofasciotomies were performed bilaterally on 14 cadaveric specimens (28 legs). Next, we performed transverse fasciotomies on 1 limb and performed extensions of the longitudinal incision on the contralateral limb. Subsequent changes in compartment pressures were recorded after each release. Two-tailed paired and unpaired Student t tests were performed for statistical analysis with significance set at P < 0.05. SETTING: Anatomy laboratory. RESULTS: After a 10-cm longitudinal dermatofasciotomy, the average compartment pressure was 17 +/- 7.1 mm Hg proximally and 15.5 +/- 7.4 mm Hg distally. With an extensile 16-cm longitudinal incision, a significant decrease in compartment pressure was seen both proximally (6.5 +/- 3.1 mm Hg) and distally (4.7 +/- 4.7 mm Hg). With adjunctive transverse fasciotomies, a significant reduction in compartment pressure also was observed proximally (6.9 +/- 6.1 mm Hg) and distally (6.1 +/- 5.4 mm Hg). There was no statistically significant difference in compartment pressures between an extensile 16-cm incision and 10-cm incision combined with transverse fasciotomies both proximally and distally (P = 0.84 and P = 0.5, respectively). CONCLUSIONS: A combined approach of transverse fasciotomies with a limited longitudinal dermatofasciotomy in this in vitro compartment syndrome study is as effective as a standard 16-cm longitudinal release in the anterior compartment of this cadaveric leg model.

Anterior Compartment Syndrome↗
PubMed2005

Regional variation in ICC distribution, pacemaking activity and neural responses in the longitudinal muscle of the murine stomach.

Intramuscular interstitial cells of Cajal (ICC-IM) play a critical role in enteric neural regulation of the circular muscle layer in the stomach, but no studies have been performed on the longitudinal layer. Kit immunohistochemistry was used to examine ICC-IM in the longitudinal muscle layer of the murine corpus and antrum, and it revealed marked heterogeneity in the distribution of ICC-IM in longitudinal muscles. In the corpus, ICC-IM were found along the greater curvature near the fundus. ICC-IM decreased in density in the circumferential axis toward the lesser curvature and in the longitudinal axis toward the antrum. ICC-IM were absent from the longitudinal layer of the antrum. Double labelling with markers for specific classes of enteric motor neurones revealed that cholinergic and nitrergic motor neurones formed close contacts with ICC-IM in the corpus but not in the antrum. Enteric nerve stimulation evoked prominent cholinergic excitatory and nitrergic inhibitory responses in longitudinal muscles of the corpus, but not in the antrum of wild-type animals. Cholinergic and nitrergic nerves were also present in W/W(V) mice, but functional innervation of the longitudinal muscle layer by these nerves in the corpus and antrum were absent. The data show that cholinergic and nitrergic neurotransmission only occurs in the gastric longitudinal layer in regions where ICC-IM are present. In regions, such as the corpus, where ICC-IM are common, robust neural responses are present, but the reduced density of ICC-IM near the lesser curvature and in the distal stomach leads to reduced neural regulation in these gastric regions.

Animals↗
PubMed1994

Longitudinal image deblurring in spiral CT.

PURPOSE: To assess the feasibility of digital deconvolution techniques to improve longitudinal resolution of spiral computed tomography (CT) multiplanar reformations and evaluate how technical factors in deconvolution affect longitudinal resolution, noise, and edge ringing. MATERIALS AND METHODS: Longitudinal line spread function (LSF) of the system was estimated from longitudinal reformations of transaxial spiral CT images of a step test phantom. By using the estimated LSF, longitudinal reformations of the phantom and three clinical spiral CT studies were deconvolved by the methods of Wiener filtering and constrained iterative deconvolution. Edge ringing and image noise were quantified for Wiener filtering and constrained iterative deconvolution. RESULTS: Longitudinal reformations were substantially deblurred and resolution improved after deconvolution. Anatomic boundaries in clinical images were more clearly delineated after restoration. The methods of Wiener deconvolution and constrained iterative deconvolution improved the sharpness of the phantom step boundary at the expense of increased edge ringing and image noise. CONCLUSION: In longitudinal spiral CT reformations, blurring along the longitudinal axis can be reduced by Wiener filtering or constrained iterative deconvolution.

Technology, Radiologic↗
PubMed1982

Responsiveness of longitudinal and circular muscle layers of the portal vein.

This study was performed to compare mechanical activity produced by acetylcholine and histamine in longitudinal and circular muscle layers of the portal vein. Peak tension was measured in longitudinal and circular muscle strips from portal veins of rabbits as they were superfused with acetylcholine and histamine (10(-6) to 10(-4) M). Responses to acetylcholine were three to four times greater in longitudinal muscle than in circular muscle; for example, acetylcholine (10(-5) M) produced contractions of 1.6 +/- 0.2 X 10(3) (mean +/- SE) dynes in longitudinal muscle and 0.4 +/- 0.09 X 10(3) dynes in circular muscle. In the same strips, histamine produced similar responses in the two layers: histamine (10(-5) M) produced contractions of 0.4 +/- 0.1 X 10(3) dynes in longitudinal and 0.4 +/- 0.1 X 10(3) dynes in circular muscle. Histological studies of portal vein muscle strips showed that the longitudinal muscle layer is three to four times thicker than the circular muscle layer. Thus, in response to acetylcholine, tension developed in each muscle layer is proportional to the thickness of that layer. In response to histamine, however, longitudinal muscle develops less tension than is predicted by the thickness of the muscle layer. We conclude that longitudinal and circular muscle layers of the rabbit portal vein differ in their responsiveness to histamine.

Acetylcholine↗
PubMed1984

Swallowing induces sequential activation of esophageal longitudinal smooth muscle.

We examined the mechanical activity of the longitudinal and circular muscles of the esophagus at three different levels (9, 5, and 1 cm above the lower esophageal sphincter) during peristalsis induced by swallows or vagal stimulation in anesthetized opossums with miniature strain gauges applied in the axis of muscle fibers. The onset of longitudinal muscle contraction occurred in an aboral sequence with swallows but simultaneously with vagal stimulation. The speed of longitudinal muscle activation with swallows was 7.6 +/- 1.7 cm/s. Circular muscle contraction occurred in an aboral sequence with vagal stimulation and swallowing with speeds of 4.1 +/- 0.8 and 2.3 +/- 0.1 cm/s, respectively. Longitudinal muscle contracted before the circular muscle at all sites. The duration of longitudinal muscle contraction increased aborally (P less than 0.05) with swallowing or vagal stimulation. These studies show that 1) during swallowing, esophageal longitudinal and circular smooth muscle contract in a sequential fashion, 2) the longitudinal muscle sequential contraction is due to central mechanisms, whereas circular muscle sequential contraction may be due to both central and peripheral mechanisms, and 3) peripheral neuromuscular mechanisms produce regional differences in the duration of longitudinal muscle contraction.

Animals↗
PubMed1999

Differential inflammatory modulation of canine ileal longitudinal and circular muscle cells.

The aim of this study was to identify the subtypes of muscarinic receptors that mediate in vivo and in vitro canine ileal longitudinal muscle contractions and whether their role is modulated by inflammation. Previous studies have reported that circular muscle contractions are suppressed in ileal inflammation induced by mucosal exposure to ethanol and acetic acid. We found that inflammation had no significant effect on in vivo and in vitro spontaneous or muscarinic receptor-mediated contractions of the longitudinal muscle. The longitudinal muscle contractions were mediated primarily by the M(3) receptor subtype. However, the IC(50) of the M(2) receptor antagonist methoctramine was only 10 times greater than that of the M(3) receptor antagonist 4-DAMP in the longitudinal muscle, whereas it was 224 times greater in the circular muscle. M(2) receptor-coupled decrease of intracellular cAMP occurred in the longitudinal but not in the circular muscle from the normal ileum. Inflammation did not alter this coupling in the longitudinal muscle but established it in the circular muscle. In conclusion, M(2) receptors may play a greater role in the mediation of longitudinal muscle contractions than circular muscle contractions. Inflammation does not alter the contractility or the relative role of muscarinic receptor subtypes in longitudinal muscle cells. However, it modulates the M(2) receptor coupling to adenylate cyclase in the circular muscle.

Adenylyl Cyclases↗
PubMed2005

Upper-extremity phocomelia reexamined: a longitudinal dysplasia.

BACKGROUND: In contrast to longitudinal deficiencies, phocomelia is considered a transverse, intercalated segmental dysplasia. Most patients demonstrate severe, but not otherwise classifiable, upper-extremity deformities, which usually cannot be placed into one of three previously described phocomelia groups. Additionally, these phocomelic extremities do not demonstrate true segmental deficits; the limb is also abnormal proximal and distal to the segmental defect. The purpose of this investigation was to present evidence that upper-extremity abnormalities in patients previously diagnosed as having phocomelia in fact represent a proximal continuum of radial or ulnar longitudinal dysplasia. METHODS: The charts and radiographs of forty-one patients (sixty extremities) diagnosed as having upper-extremity phocomelia were reviewed retrospectively. On the basis of the findings on the radiographs, the disorders were categorized into three groups: (1) proximal radial longitudinal dysplasia, which was characterized by an absent proximal part of the humerus, a nearly normal distal part of the humerus, a completely absent radius, and a radial-sided hand dysplasia; (2) proximal ulnar longitudinal dysplasia, characterized by a short one-bone upper extremity that bifurcated distally and by severe hand abnormalities compatible with ulnar dysplasia; and (3) severe combined dysplasia, with type A characterized by an absence of the forearm segment (i.e., the radius and ulna) and type B characterized by absence of the arm and forearm (i.e., the hand attached to the thorax). RESULTS: Twenty-nine limbs in sixteen patients could be classified as having proximal radial longitudinal dysplasia. Systemic medical conditions such as thrombocytopenia-absent radius syndrome were common in those patients, but additional musculoskeletal conditions were rare. Twenty limbs in seventeen patients could be classified as having proximal ulnar longitudinal dysplasia. Associated musculoskeletal abnormalities, such as proximal femoral focal deficiency, were common in those patients. Eleven limbs in ten patients were identified as having severe combined dysplasia, which was type A in seven of them and type B in four. Four patients with severe combined dysplasia had congenital cardiac anomalies, and four had associated musculoskeletal abnormalities. Three of the four patients with the type-B disorder had a contralateral ulnar longitudinal dysplasia. CONCLUSIONS: We propose that cases previously classified as upper-extremity phocomelia represent a spectrum of severe longitudinal dysplasia, as none of the sixty extremities that we studied demonstrated a true intercalary deficiency. These findings have both developmental and genetic implications.

Child↗
PubMedDate not supplied

Longitudinal forces acting at side-to-end and end-to-side anastomoses when a knitted polyester arterial prosthesis is implanted in the dog.

In a previous study, which investigated the tensions at the proximal and distal end-to-end anastomoses of a vascular prosthesis, no significant differences were found in the longitudinal forces between the two anastomotic sites after different periods of implantation. The present follow-up study was devised to study the longitudinal forces at a proximal side-to-end and a distal end-to-side anastomosis using a warp knitted polyester prosthesis implanted as a canine thorocoabdominal bypass. The external surface of the prosthesis contained a specially printed "tension indicator" design, which enabled changes in length to be assessed photographically at the two anastomoses at the time of implantation and at sacrifice. The longitudinal force at each site was then calculated using a relationship obtained experimentally between the total longitudinal force and the changes in length of the virgin graft in vitro. The in vitro measurements on the prosthesis were performed using a computer-controlled laser calibration system. Although the results showed a tendency toward a gradual loss in longitudinal force at both anastomoses over 7 months in situ, statistical analysis showed no significant difference in the longitudinal force at the two anastomotic sites after any period of implantation. Histopathological and textile analysis also showed that the characteristics of the prostheses were similar at both anastomotic sites. This does not mean, however, that the intramural stress concentrations experienced by the two sites were the same. While comparing the level of the longitudinal forces measured in this study with those observed in the previous thoracic aorta study using end-to-end anastomoses, no significant differences were observed due to the different types of anastomoses. It would appear that the longitudinal force is not one of the main etiological factors that cause the formation and localization of anastomotic failure.

Anastomosis, Surgical↗
PubMedDate not supplied

Use of the longitudinal arch angle to predict dynamic foot posture in walking.

To determine whether differences exist in the longitudinal arch angle based on sex or extremity, the longitudinal arch angle was assessed in 21 men and 21 women using a digital image of the medial aspect of each subject's feet. The image was obtained with the subject in relaxed standing posture and in maximum internal rotation of the lower leg. To determine whether the longitudinal arch angle could be used to predict dynamic foot posture during walking, 50 different subjects were asked to walk across a 6-m walkway while the medial aspect of each foot was videotaped. The longitudinal arch angle was digitized from digital images obtained at midstance for three walking trials. No differences in the longitudinal arch angle were found based on sex or extremity. The longitudinal arch angles obtained in the static positions of relaxed standing posture and maximum internal rotation were highly predictive of dynamic foot posture at midstance during walking. Relaxed standing posture and maximum internal rotation significantly contributed to explaining more than 90% of the variance associated with the longitudinal arch angle position at midstance during walking. These results validate use of the longitudinal arch angle as part of the foot and ankle physical examination.

Adult↗
PubMed2003

Left ventricular longitudinal shortening in patients with aortic stenosis: relationship with symptomatic status.

BACKGROUND AND AIM OF THE STUDY: Symptomatic status in aortic stenosis is not always related to hemodynamic severity as estimated by the aortic valve effective orifice area (AVA), and other factors may be involved. It has been seen previously that, whilst ejection fraction is preserved, left ventricular (LV) longitudinal shortening may be selectively decreased in aortic stenosis, and hypothesized that this might be a marker of subendocardial ischemia as subendocardial myocardial fibers are oriented longitudinally. The present study examined the possible relationship between LV longitudinal shortening and symptoms in patients with aortic stenosis. METHODS: Relevant clinical and echocardiographic variables, including the percentage of LV longitudinal shortening, were measured in 131 consecutive patients with at least moderate aortic stenosis (AVA <1.5 cm2). RESULTS: Symptoms were found in 106 patients (exertional dyspnea 93%, resting dyspnea 25%, angina 57%, syncope 27%). Compared with asymptomatic patients, symptomatic patients had a smaller AVA (0.91 +/- 0.27 versus 1.13 +/- 0.20 cm2; p < 0.001), a lower LV longitudinal shortening (19 +/- 13 versus 28 +/- 9%; p = 0.01), and higher incidence of coronary artery disease (52 versus 20%, p < 0.008). Other variables significantly associated with symptoms included age, previous myocardial infarction, obesity, indexed AVA, LV mass index, LV ejection fraction, cardiac index, energy loss index, and valvular resistance. However, in multivariate analysis, the only variables independently associated with symptomatic status were patient age (p = 0.03), indexed AVA (p = 0.006), and LV longitudinal shortening (p = 0.04). The combination of indexed AVA with LV longitudinal shortening resulted in an improvement of the performance for the prediction of symptoms. CONCLUSION: These results show that LV longitudinal shortening is more closely associated with changes in symptomatic status than other currently used indices of LV systolic function. As such, it probably more closely reflects alterations in subendocardial myocardial function.

Age Factors↗
PubMed1982

Sensitivity of circular and longitudinal uterine muscles to noradrenaline.

Spontaneous contractions of circular and longitudinal uterine muscles of rat and rabbit during estrogen domination were recorded in vitro isometrically. The circular muscles of both uteri contracted more frequently than the longitudinal muscles. Noradrenaline inhibited the spontaneous contractions of the longitudinal (ED50 = 5x10(-7) M) and circular (ED50 = 4.9x10(-6) M) rat uterine muscles. One molecule of noradrenaline bound 0.35 receptors in the circular and 0.63 receptors in the longitudinal rat muscles. Noradrenaline increased both amplitude and frequency of the rabbit uterine contractions (ED50 = 5.8x10(-9) M for the circular and 1x10(-7) M for the longitudinal muscles). One molecule of noradrenaline bound 0.63 receptors in the circular and 0.84 receptors in the longitudinal muscle of the rabbit uterus. The response of the longitudinal rabbit muscle to noradrenaline was influenced by D-600 to a larger degree than that of the circular muscle. The different sensitivity to noradrenaline of the circular and longitudinal uterine muscles may be explained by the different number of adrenoceptors and their binding sites as well as by some differences in calcium utilization.

Animals↗
PubMed1989

Noncomparability of cross-sectional and longitudinal estimates of lung growth in children.

Results from longitudinal and cross-sectional studies of pulmonary function are often compared. However, previous studies in adults suggest that results from longitudinal and cross-sectional studies are different and may not be comparable. In order to evaluate these differences further, prospectively collected data in a group of children were analyzed by both longitudinal and cross-sectional methods. Spirometry was performed longitudinally over a period of 8 years on 58 healthy children. Straight-line regressions of expiratory flow-volume parameters on height were computed by averaging the individual regression lines for each child. A cross-sectional sample from these same children was analyzed and compared to the longitudinal analysis. For all expiratory flow-volume parameters, the cross-sectional analysis resulted in a significantly greater increase in growth with increasing height than the longitudinal analysis (P less than 0.005 for slope for all parameters except PEFR, P less than 0.05 and Vmax75, P less than 0.01). These differences cannot be explained by learning or horse-racing effects, loss to follow-up, or regression to the mean; however, they could be explained by cohort changes, time trends of pulmonary function, differences in the weighted averages used in the two analyses, or incorrect modeling. These observations indicate that comparisons between cross-sectional and longitudinal investigations must be made cautiously. These data do not support many of the reasons suggested for the differences in previous reports. It is recommended that studies of pulmonary function use a control group and investigate the groups at the same time and in the same manner.

Body Height↗
PubMed2006

Neural networks for longitudinal studies in Alzheimer's disease.

OBJECTIVE: Alzheimer's disease affects a growing population of elderly people today. The predictions about the course of the disease is a key component of health care decision making for patients with Alzheimer's. The physician's prognosis and predicted trajectory of cognitive decline often form the basis of treatment and health care decisions taken by patients and their families. These predictions are difficult to make because of the high variability and non-linearity exhibited by individual patterns of cognitive decline. This paper presents a new method of predicting the course of a disease using longitudinal data collected through multiple clinic visits. Longitudinal databases are similar to temporal databases, with some important differences--data is collected at irregular time intervals that are patient specific and also a varying number of observations are made for each patient, depending upon the number of times the patient visited the clinic. We propose a new type of neural network called the mixed effects neural network (MENN) model that can incorporate this type of longitudinal information. MATERIAL AND METHODS: We have used longitudinal data on 704 subjects enrolled at the Layton aging and research center (LAARC) at Oregon Health and Science University. A back-propagation algorithm, modified for longitudinal data is used to obtain the weight parameters of the MENN. The modified back-propagation algorithm is further embedded in an iterative procedure that estimates the noise variance and the parameters that capture the longitudinal (temporal) correlation structure. RESULTS: We have compared the performance of the MENN with linear mixed effects models and standard neural networks (NN). MENN show better performance (misclassification rate = 0.13 and relative MSE = 0.35) as compared to standard NN (misclassification rate = 0.34 and relative MSE = 2.74) and linear mixed effects models (misclassification rate = 0.14 and relative MSE = 0.4). CONCLUSION: The results show that this method can be a useful tool for predicting non-linear disease trajectories and uncovering significant prognostic factors in longitudinal databases.

Aged↗
PubMed2003

Effects of physical activity on emotional well-being among older Australian women: cross-sectional and longitudinal analyses.

OBJECTIVE: To explore relationships between physical activity and mental health cross-sectionally and longitudinally in a large cohort of older Australian women. METHOD: Women in their 70s participating in the Australian Longitudinal Study on Women's Health responded in 1996 (aged 70-75) and in 1999 (aged 73-78). Cross-sectional data were analyzed for 10,063 women and longitudinal data for 6472. Self-reports were used to categorize women into four categories of physical activity at each time point as well as to define four physical activity transition categories across the 3-year period. Outcome variables for the cross-sectional analyses were the mental health component score (MCS) and mental health subscales of the Medical Outcomes Study Short Form (SF-36). The longitudinal analyses focused on changes in these variables. Confounders included the physical health component scale (PCS) of the SF-36, marital status, body mass index (BMI) and life events. Adjustment for baseline scores was included for the longitudinal analyses. RESULTS: Cross-sectionally, higher levels of physical activity were associated with higher scores on all dependent variables, both with and without adjustment for confounders. Longitudinally, the effects were weaker, but women who had made a transition from some physical activity to none generally showed more negative changes in emotional well-being than those who had always been sedentary, while those who maintained or adopted physical activity had better outcomes. CONCLUSION: Physical activity is associated with emotional well-being among a population cohort of older women both cross-sectionally and longitudinally, supporting the need for the promotion of appropriate physical activity in this age group.

Aged↗
PubMed2002

Attrition in longitudinal studies. How to deal with missing data.

The purpose of this paper was to illustrate the influence of missing data on the results of longitudinal statistical analyses [i.e., MANOVA for repeated measurements and Generalised Estimating Equations (GEE)] and to illustrate the influence of using different imputation methods to replace missing data. Besides a complete dataset, four incomplete datasets were considered: two datasets with 10% missing data and two datasets with 25% missing data. In both situations missingness was considered independent and dependent on observed data. Imputation methods were divided into cross-sectional methods (i.e., mean of series, hot deck, and cross-sectional regression) and longitudinal methods (i.e., last value carried forward, longitudinal interpolation, and longitudinal regression). Besides these, also the multiple imputation method was applied and discussed. The analyses were performed on a particular (observational) longitudinal dataset, with particular missing data patterns and imputation methods. The results of this illustration shows that when MANOVA for repeated measurements is used, imputation methods are highly recommendable (because MANOVA as implemented in the software used, uses listwise deletion of cases with a missing value). Applying GEE analysis, imputation methods were not necessary. When imputation methods were used, longitudinal imputation methods were often preferable above cross-sectional imputation methods, in a way that the point estimates and standard errors were closer to the estimates derived from the complete dataset. Furthermore, this study showed that the theoretically more valid multiple imputation method did not lead to different point estimates than the more simple (longitudinal) imputation methods. However, the estimated standard errors appeared to be theoretically more adequate, because they reflect the uncertainty in estimation caused by missing values.

Analysis of Variance↗