Validation of a New Simple Scale to Measure Symptoms in Atrial Fibrillation

Background— Atrial fibrillation (AF) is commonly associated with impaired quality of life. There is no simple validated scale to quantify the functional illness burden of AF. The Canadian Cardiovascular Society Severity in Atrial Fibrillation (CCS-SAF) scale is a bedside scale that ranges from class 0 to 4, from no effect on functional quality of life to a severe effect on life quality. This study was performed to validate the scale.

Methods and Results— In 484 patients with documented AF (62.2�12.5 years of age, 67% men; 62% paroxysmal and 38% persistent/permanent), the SAF class was assessed and 2 validated quality-of-life questionnaires were administered: the SF-36 generic scale and the disease-specific AFSS (University of Toronto Atrial Fibrillation Severity Scale). There is a significant linear graded correlation between the SAF class and measures of symptom severity, physical and emotional components of quality of life, general well-being, and health care consumption related to AF. Patients with SAF class 0 had age- and sex-standardized SF-36 scores of 0.15�0.16 and −0.04�0.31 (SD units), that is, units away from the mean population score for the mental and physical summary scores, respectively. For each unit increase in SAF class, there is a 0.36 and 0.40 SD unit decrease in the SF-36 score for the physical and mental components. As the SAF class increases from 0 to 4, the symptom severity score (range, 0 to 35) increases from 4.2�5.0 to 18.4�7.8 ( P <0.0001).

Conclusions— The CCS-SAF scale is a simple semiquantitative scale that closely approximates patient-reported subjective measures of quality of life in AF and may be practical for clinical use.

A prevention strategy to reduce the incidence of injury in high school basketball: a cluster randomized controlled trial

OBJECTIVE

To examine the effectiveness of a sport-specific balance training program in reducing injury in adolescent basketball.

DESIGN

Cluster randomized controlled trial.

SETTING

Twenty-five high schools in Calgary and surrounding area.

SUBJECTS

Nine hundred and twenty high school basketball players (ages 12-18).

INTERVENTION

Subjects were randomly allocated by school to the control (n = 426) and training group (n = 494). Both groups were taught a standardized warm-up program. The training group was also taught an additional warm-up component and a home-based balance training program using a wobble board.

MAIN OUTCOME MEASURES

All injuries occurring during basketball that required medical attention and/or caused a player to be removed from that current session and/or miss a subsequent session were then recorded and assessed by a team therapist who was blinded to training group allocation.

RESULTS

A basketball-specific balance training program was protective of acute-onset injuries in high school basketball [RR = 0.71 (95% CI; 0.5-0.99)]. The protective effect found with respect to all injury [RR = 0.8 (95% CI; 0.57-1.11)], lower-extremity injury [RR = 0.83 (95% CI; 0.57-1.19)], and ankle sprain injury [RR = 0.71 (95% CI; 0.45-1.13)] were not statistically significant. Self-reported compliance to the intended home-based training program was poor (298/494 or 60.3%).

CONCLUSIONS

A basketball-specific balance training program was effective in reducing acute-onset injuries in high school basketball. There was also a clinically relevant trend found with respect to the reduction of all, lower-extremity, and ankle sprain injury. Future research should include further development of neuromuscular prevention strategies in addition to further evaluation of methods to increase compliance to an injury-prevention training program in adolescents.

Long-term effectiveness of extracorporeal shockwave therapy in the treatment of previously untreated lateral epicondylitis

OBJECTIVE

To describe the outcomes of a cohort of individuals involved in a randomized control trial of extracorporeal shockwave therapy (ESWT) in the treatment of lateral epicondylitis (LE) not previously treated.

DESIGN

Prospective cohort.

SETTING

General population.

PATIENTS

Sixty subjects (23 female, 37 male) who participated in a double-blind randomized control trial on the effectiveness of ESWT in the treatment of LE. All subjects had previously not received therapy for their LE.

INTERVENTION

At the 8-week follow-up of a randomized control trial comparing ESWT with a stretching protocol for treatment of LE, all subjects were unblinded to their treatment allocation, and subjects initially allocated to sham therapy were offered active therapy.

MAIN OUTCOME MEASURES

Overall elbow pain (10-cm visual analogue scale [VAS]) and maximum pain-free grip strength were evaluated at 0, 4, and 8 weeks and 3, 6, and 9 to 12 months postinitiation of therapy. Time to pain-free status (less than 1 cm on the VAS) was calculated from time of onset of symptoms, time of inclusion into the trial, and time from initiation of active therapy.

MAIN RESULTS

A statistically significant difference in time to pain-free status was not detected between groups. Duration of symptoms was identified to be an effect modifier of early response to therapy (at least 50% improvement on the VAS at 8-week postinitiation of therapy). A higher proportion of subjects treated within 16 weeks of onset of LE symptoms showed a response to ESWT than subjects treated after 16 weeks of onset of their LE symptoms.

CONCLUSIONS

The use of ESWT with a stretching program is not supported by this study, with the possible exception of the possible interaction effect of time of ESWT initiation from the time of onset of symptoms, which requires further investigation.

Muon spin relaxation and isotropic pairing in superconducting PrOs4Sb12

Transverse-field muon-spin rotation measurements in the vortex-lattice of the heavy-fermion (HF) superconductor PrOs4Sb12 yield a temperature dependence of the magnetic penetration depth lambda indicative of an isotropic or nearly isotropic energy gap. This is not seen to date in any other HF superconductor and is a signature of isotropic pairing symmetry, possibly related to a novel nonmagnetic "quadrupolar Kondo" HF mechanism in PrOs4Sb12. The T=0 relaxation rate sigma(s)(0)=0.91(1) micros(-1) yields an estimated magnetic penetration depth lambda(0)=3440(20) A, which is considerably shorter than in other HF superconductors.

The impact of face shield use on concussions in ice hockey: a multivariate analysis

OBJECTIVE

To identify specific risk factors for concussion severity among ice hockey players wearing full face shields compared with half face shields (visors).

METHODS

A prospective cohort study was conducted during one varsity hockey season (1997-1998) with 642 male ice hockey players (median age 22 years) from 22 teams participating in the Canadian Inter-University Athletics Union. Half of the teams wore full face shields, and half wore half shields (visors) for every practice and game throughout the season. Team therapists and doctors recorded on structured forms daily injury, participation, and information on face shield use for each athlete. The main outcome measure was any traumatic brain injury requiring assessment or treatment by a team therapist or doctor, categorised by time lost from subsequent participation and compared by type of face shield worn.

RESULTS

Players who wore half face shields missed significantly more practices and games per concussion (2.4 times) than players who wore full face shields (4.07 sessions (95% confidence interval (CI) 3.48 to 4.74) v 1.71 sessions (95% CI 1.32 to 2.18) respectively). Significantly more playing time was lost by players wearing half shields during practices and games, and did not depend on whether the athletes were forwards or defence, rookies or veterans, or whether the concussions were new or recurrent. In addition, players who wore half face shields and no mouthguards at the time of concussion missed significantly more playing time (5.57 sessions per concussion; 95% CI 4.40 to 6.95) than players who wore half shields and mouthguards (2.76 sessions per concussion; 95% CI 2.14 to 3.55). Players who wore full face shields and mouthguards at the time of concussion lost no playing time compared with 1.80 sessions lost per concussion (95% CI 1.38 to 2.34) for players wearing full face shields and no mouthguards.

CONCLUSIONS

The use of a full face shield compared with half face shield by intercollegiate ice hockey players significantly reduced the playing time lost because of concussion, suggesting that concussion severity may be reduced by the use of a full face shield.

Sumatriptan responsiveness and clinical, psychiatric and psychologic features in migraine patients

OBJECTIVE

To compare sumatriptan responders and nonresponders in a migraine population with regard to a number of clinical, psychiatric and psychologic features.

METHODS

Patients were drawn from a referral headache clinic population, and classified as responders or nonresponders. Clinical features were assessed by a written questionnaire. The lifetime prevalence of several psychiatric disorders was determined by the National Institute of Mental Health diagnostic interview schedule and personality factors were measured by the 16 Personality Factors (16PF) Questionnaire.

RESULTS

Nonresponders indicated less influence on their migraine by menstrual factors, had a higher lifetime prevalence of generalized anxiety, and showed 16PF scores indicating greater shyness, self-sufficiency and perfectionism. Nonresponders were also more imaginative and less socially outgoing.

CONCLUSION

Although they must be interpreted with caution due to small sample size and the multiple comparisons made, our results indicate that there may be differences between sumatriptan responders and nonresponders with regard to a number of clinical, psychiatric and psychologic factors. These results suggest that biological differences exist between the two patient groups which likely account for both the differences in their responses to sumatriptan and in the clinical features noted above.

Over-expression of the cercosporin facilitator protein, CFP, in Cercospora kikuchii up-regulates production and secretion of cercosporin

CFP (cercosporin facilitator protein), a light-regulated gene from the soybean fungal pathogen Cercospora kikuchii, encodes the putative major facilitator transporter of the fungal polyketide cercosporin. Gene disruption of CFP in C. kikuchii strain Gus-3 resulted in dramatically reduced cercosporin production and virulence, and increased sensitivity to the toxin. Two C. kikuchii transformant strains (10-1 and 10-11) that over-produce cercosporin were recovered from the complementation of CFP gene-disrupted strain Gus-3. Southern analysis revealed that these strains contained multiple genomic copies of CFP and over-expressed CFP transcript and protein. Although 10-1 and 10-11 produce and secrete significantly elevated levels of cercosporin, they exhibit wild-type resistance to cercosporin, and maintain a wild-type pattern of light-regulated toxin accumulation. Restoration of wild-type cercosporin resistance in 10-1 and 10-11 suggests that CFP does contribute substantially to cercosporin resistance via toxin secretion. The three-fold increase in toxin accumulation, predominantly associated with the mycelium fraction of these CFP multi-copy strains, suggests that CFP may also have a significant, but unknown, role in regulating toxin production.

Glassy spin dynamics in non-fermi-liquid UCu5-xPdx, x = 1.0 and 1.5

Local f-electron spin dynamics in the non-Fermi-liquid heavy-fermion alloys UCu5-xPdx, x = 1.0 and 1.5, have been studied using muon spin-lattice relaxation. The sample-averaged asymmetry function G(t) indicates strongly inhomogeneous spin fluctuations and exhibits the scaling G(t,H) = G(t/H(gamma)) expected from glassy dynamics. At 0.05 K gamma(x = 1.0) = 0.35+/-0.1, but gamma(x = 1.5) = 0.7+/-0.1. This is in contrast to inelastic neutron scattering results, which yield gamma = 0.33 for both concentrations. There is no sign of static magnetism approximately greater than 10(-3)(B)/U ion in either material above 0.05 K. Our results strongly suggest that both alloys are quantum spin glasses.

Distribution of patients' paroxysmal atrial tachyarrhythmia episodes: implications for detection of treatment efficacy

INTRODUCTION

Clinical trials of treatments for paroxysmal atrial tachyarrhythmia (pAT) often compare different treatment groups using the time to first episode recurrence. This approach assumes that the time to the first recurrence is representative of all times between successive episodes in a given patient. We subjected this assumption to an empiric test.

METHODS AND RESULTS

Records of pAT onsets from a chronologic series of 134 patients with dual chamber implantable defibrillators were analyzed; 14 had experienced >10 pAT episodes, which is sufficient for meaningful statistical modeling of the time intervals between episodes. Episodes were independent and randomly distributed in 9 of 14 patients, but a fit of the data to an exponential distribution, required by the stated assumption, was rejected in 13 of 14. In contrast, a Weibull distribution yielded an adequate goodness of fit in 5 of the 9 cases with independent and randomly distributed data. Monte Carlo methods were used to determine the impact of violations of the exponential distribution assumption on clinical trials using time from cardioversion to first episode recurrence as the dependent measure. In a parallel groups design, substantial loss of power occurs with sample sizes <500 patients per group. In a cross-over design, there is insufficient power to detect a 30% reduction in episode frequency even with 300 patients.

CONCLUSION

Clinical trials that rely on time to first episode recurrence may be considerably less able to detect efficacious treatments than may have been supposed. Analysis of multiple episode onsets recorded over time should be used to avoid this pitfall.

Simulated microgravity [bed rest] has little influence on taste, odor or trigeminal sensitivity

Anecdotal evidence suggests that astronauts' perceptions of foods in space flight may differ from their perceptions of the same foods on Earth. Fluid shifts toward the head experienced in space may alter the astronauts' sensitivity to odors and tastes, producing altered perceptions. Our objective was to determine whether head-down bed rest, which produces similar fluid shifts, would produce changes in sensitivity to taste, odor or trigeminal sensations. Six subjects were rested three times prior to bed rest, three times during bed rest and two times after bed rest to determine their threshold sensitivity to the odors isoamylbutyrate and menthone, the tastants sucrose, sodium chloride, citric acid, quinine and monosodium glutamate, and to capsaicin. Thresholds were measured using a modified staircase procedure. Self-reported congestion was also recorded at each test time. Thresholds for monosodium glutamate where slightly higher during bed rest. None of the other thresholds were altered by bed rest.

The relationship between health-related quality of life and frequency of spells in patients with syncope

Chronic syncope has a wide range of symptom burden, and anecdotal data suggest substantial but variable physical and psychosocial morbidity. We hypothesized that health-related quality of life (HRQL) is impaired in syncope patients and the degree of impairment is proportional to syncope frequency. The EuroQol EQ-5D was completed by 136 patients (79 female and 57 male) with mean age 40 (SD = 17) prior to assessment. HRQL was substantially impaired in syncope patients compared to population norms in all five dimensions of health measured by the EQ-5D. In patients with six or more lifetime syncopal spells there was a significant (P < 0.001) negative relationship between the frequency of spells and overall perception of health, which was not evident in those who had a history of less than six lifetime spells. These relationships were maintained after controlling for comorbid conditions.

Randomized crossover comparison of DDDR versus VDD pacing after atrioventricular junction ablation for prevention of atrial fibrillation. The atrial pacing peri-ablation for paroxysmal atrial fibrillation (PA (3)) study investigators

BACKGROUND

Some clinical data suggest that atrial-based pacing prevents paroxysmal atrial fibrillation (AF). This study tested the hypothesis that DDDR pacing compared with VDD pacing prevents AF after atrioventricular (AV) junction ablation.

METHODS AND RESULTS

Patients were randomized to DDDR pacing (n=33) or to VDD pacing (n=34) after AV junction ablation and followed every 2 months for 6 months. Patients then crossed over to the alternate pacing mode and were followed for an additional 6 months. Primary analysis included the time to first recurrence of sustained AF (duration >5 minutes), total AF burden, and the development of permanent AF. The time to first episode of AF was similar in the DDDR group (0.37 days, 95% CI 0.1 to 1.3 days) and the VDD pacing group (0.5 days, 95% CI 0.2 to 1.7 days, P=NS). AF burden increased over time in both groups (P<0.01). At the 6-month follow-up, AF burden was 6.93 h/d (95% CI 4. 37 to 10.96 h/d) in the DDDR group and 6.30 h/d (95% CI 3.99 to 9.94 h/d) in the VDD group (P=NS). Twelve (35%) patients in the DDDR group and 11 (32%) patients in the VDD group had permanent AF within 6 months of ablation. Within 1 year of follow-up, 43% of patients had permanent AF.

CONCLUSIONS

DDDR pacing compared with VDD pacing does not prevent paroxysmal AF over the long term in patients in the absence of antiarrhythmic drug therapy after total AV junction ablation. Many patients have permanent AF within the first year after ablation.

The effect of long-term care environments on health outcomes

This study contrasts rates of mortality and of relocation to higher levels of care as well as trajectories of cognitive status, functional ability, depression, and subjective health of residents of an assisted living facility with those of a nursing home. Data were collected from medical records and face-to-face interviews with 158 residents at baseline and 4, 8, and 12 months later. All participants lived on a single long-term care campus. Logistic regression revealed that facility was not a significant predictor of mortality or relocations due to declining health. A repeated measures analysis of variance found that outcomes for people living in the two facilities did not change at different rates. These consistent findings suggest that although the assisted living and nursing home environments claim to have different philosophies of care, health outcome patterns for people living in the two environments were similar.

Temporal patterns of paroxysmal atrial fibrillation following DDDR pacemaker implantation

Paroxysmal atrial fibrillation (AF) episodes have been reported to be randomly distributed. However, because patients are not always symptomatic, it has been difficult to study temporal patterns of AF. Newer implantable pulse generators have data-logging capabilities that permit the detection and analysis of temporal patterns of AF. This study tested the hypothesis that AF episodes occur in clusters over time and that these episodes are not randomly distributed in individual patients. The date and time of 582 episodes of AF were recorded from the data logs of 16 patients with a Medtronic Thera DR followed 6 weeks and 6 and 12 months after pulse generator implant. The probability of AF recurrence and the interevent intervals between successive episodes of AF were fitted to monoexponential and Weibull distributions. A Weibull distribution best described the nonrandom distribution of AF for 67% of follow-up visits. Temporal clustering of AF (interevent intervals <24 hours) declined during follow-up (95 +/- 10%, 90 +/- 11%, and 74 +/- 28% at the 6-week and 6- and 12-month visits, respectively; p <0.05). The average duration of an episode of AF tended to increase over time (0.31 hour, 95% confidence intervals [CI] 0.17 to 0.58 hours; 0.36 hours, 95% CI 0. 17 to 0.78 hours; 0.65 hours, 95% CI 0.29 to 1.45 hours [p = 0.07] at the 6-week and 6- and 12-month visits, respectively). Paroxysmal AF recurrence is nonrandomly distributed over the long term in many patients. The temporal patterns of AF change over time after pacemaker implantation. This has implications for the selection of study end points in AF clinical trials.

Chinook winds and migraine headache

OBJECTIVE

To determine the effects of chinook weather conditions on probability of migraine headache onset.

BACKGROUND

Many migraineurs believe weather to be a trigger factor for their headaches; however, there is little supportive evidence in the literature. Migraineurs in the southern part of the Canadian province of Alberta frequently report that chinooks, warm westerly winds specific to the region, trigger their headaches.

METHOD

Weather data from Environment Canada were used to designate each calendar day during the study period as a chinook, prechinook, or nonchinook day. Headache data were collected from 75 patient diaries from the University of Calgary Headache Research Clinic. Individual and multiple logistic regression models were used to determine if the weather conditions affected the probability of migraine onset.

RESULTS

The probability of migraine onset was increased on both prechinook days (odds ratio 1.24; 95% CI 1.08 to 1.42) and on days with chinook winds (1.19; 1.02 to 1.39) compared with nonchinook days. Analysis of chinook wind velocities revealed that for chinook days, the relative risk of migraine onset was increased only on high-wind chinook days (velocity > 38 km/h) (odds ratio 1.41; 95% CI 1.06 to 1.88). A subset of individuals was sensitive to high-wind chinook days, and another subset was only sensitive to prechinook days. Only two patients were sensitive to both weather conditions, and the majority of patients was not sensitive to either. Neither weather condition had a protective effect. Increasing age was associated with high-wind chinook sensitivity (p = 0.009) but not prechinook sensitivity (p = 0.389).

CONCLUSIONS

Both prechinook and high-wind chinook days increase the probability of migraine onset in a subset of migraineurs. Because few subjects were found to be sensitive to both weather types, the mechanisms for these weather effects may be independent. This is supported by the presence of an age interaction for high-wind chinook days but not for prechinooks day.

Head and neck injuries among ice hockey players wearing full face shields vs half face shields

CONTEXT

Speculation exists that use of a full face shield by ice hockey players may increase their risk of concussions and neck injuries, offsetting the benefits of protection from dental, facial, and ocular injuries, but, to our knowledge, no data exist regarding this possibility.

OBJECTIVE

To determine the risk of sustaining a head or neck injury among intercollegiate ice hockey players wearing full face shields compared with those wearing half shields.

DESIGN, SETTING, AND PARTICIPANTS

Prospective cohort study conducted during the 1997-1998 Canadian Inter-University Athletics Union hockey season of 642 male hockey players (mean age, 22 years) from 22 teams. Athletes from 11 teams wore full face shields and athletes from 11 teams wore half face shields during play.

MAIN OUTCOME MEASURE

Reportable injury, defined as any event requiring assessment or treatment by a team therapist or physician or any mild traumatic brain injury or brachial plexus stretch, categorized by time lost from subsequent participation and compared by type of face shield.

RESULTS

Of 319 athletes who wore full face shields, 195 (61.6%) had at least 1 injury during the study season, whereas of 323 who wore half face shields, 204 (63.2 %) were injured. The risk of sustaining a facial laceration and dental injury was 2.31 (95% confidence interval [CI], 1.53-3.48; P<.001) and 9.90 (95% CI, 1.88-52.1; P = .007) times greater, respectively, for players wearing half vs full face shields. No statistically significant risk differences were found for neck injuries, concussion, or other injuries, although time lost from participation because of concussion was significantly greater in the half shield group (P<.001), than in the group wearing full shields.

CONCLUSIONS

These data provide evidence that the use of full face shields is associated with significantly reduced risk of sustaining facial and dental injuries without an increase in the risk of neck injuries, concussions, or other injuries.

Cost-utility analysis of pacemakers for the treatment of vasovagal syncope

Dual-chamber pacing is a promising treatment for patients with very frequent vasovagal syncope, but its cost utility is unknown. We report that the incremental cost per quality-adjusted life-year gained is $13,159 Canadian dollars (about $8,600 US dollars), and therefore this pacemaker therapy for vasovagal syncope has a favorable cost-utility ratio.

CFP, the putative cercosporin transporter of Cercospora kikuchii, is required for wild type cercosporin production, resistance, and virulence on soybean

Many species of the fungal genus Cercospora, including the soybean pathogen C. kikuchii, produce the phytotoxic polyketide cercosporin. Cercosporin production is induced by light. Previously, we identified several cDNA clones of mRNA transcripts that exhibited light-enhanced accumulation in C. kikuchii. Targeted disruption of the genomic copy of one of these, now designated CFP (cercosporin facilitator protein), results in a drastic reduction in cercosporin production, greatly reduced virulence of the fungus to soybean, and increased sensitivity to exogenous cercosporin. Sequence analysis of CFP reveals an 1,821-bp open reading frame encoding a 65.4-kDa protein similar to several members of the major facilitator superfamily (MFS) of integral membrane transporter proteins known to confer resistance to various antibiotics and toxins in fungi and bacteria. We propose that CFP encodes a cercosporin transporter that contributes resistance to cercosporin by actively exporting cercosporin, thus maintaining low cellular concentrations of the toxin.

Atrial pacing periablation for prevention of paroxysmal atrial fibrillation

BACKGROUND

This study tested the hypothesis that rate-adaptive atrial pacing would prevent paroxysmal atrial fibrillation (PAF) in patients with frequent PAF in the absence of symptomatic bradycardia.

METHODS AND RESULTS

Patients (n=97) with antiarrhythmic drug-refractory PAF received a Medtronic Thera DR pacemaker 3 months before planned AV node ablation. Patients were randomized to no pacing (n=48) or to atrial rate-adaptive pacing (n=49). After a 2-week stabilization period, patients were followed up for an additional 10 weeks. The time to first recurrence of sustained PAF, the interval between successive episodes of PAF, and the frequency of PAF were compared between the 2 groups in intention-to-treat analysis. Time to first episode of sustained PAF was similar in the no-pacing (4.2 days; 95% CI, 1.8 to 9.5) and the atrial-pacing (1.9 days; 95% CI, 0.8 to 4.6; P=NS) groups. PAF burden was lower in the no-pacing (0.24 h/d; 95% CI, 0.10 to 0.56) than in the atrial-pacing (0.67 h/d; 95% CI, 0.30 to 1.52; P=0.08) group. Paired crossover analysis in 11 patients revealed that time to first PAF was shorter during atrial pacing (1.6 days; 95% CI, 0.6 to 4.9) than with no pacing (6.0 days; 95% CI, 2.4 to 15.0; P=0.13), and PAF burden was greater during atrial pacing (1.00 h/d; 95% CI, 0.35 to 2.91) than with no pacing (0.32 h/d; 95% CI, 0.09 to 1.13; P<0.016).

CONCLUSIONS

Atrial rate-adaptive pacing does not prevent PAF over the short term in patients with antiarrhythmic drug-resistant PAF without symptomatic bradycardia.

Statistical issues encountered in the comparison of health-related quality of life in diseased patients to published general population norms: problems and solutions

The objectives of this study were (1) to illustrate the statistical problems encountered when comparing health-related quality of life (HRQL) measured by the Medical Outcome Study Short Form-36 (SF-36) in a diseased group to general population norms, and (2) to define age- and gender-standardized dichotomous indicator variables for each health concept and show that these indicator variables facilitate comparisons between the diseased sample and the general population. Our "diseased" group consisted of 136 sequentially consenting patients referred to the syncope clinic for assessment and treatment. Participants completed the SF-36 questionnaire before undergoing diagnostic testing. General population norms for the SF-36 are available from the responses of 2474 participants in the National Survey of Functional Health Status, conducted in 1990 in the United States. Comparison of the SF-36 in a diseased sample with general population norms is difficult, owing to skewed and unusual distributions in both groups. In addition, making comparisons within age and gender strata is difficult if the within strata sample size is small. We propose a dichotomous indicator variable for each health concept that classifies an individual as having impaired health if he or she scored lower than the 25th percentile for the appropriate age and gender general population strata. By definition, the prevalence of impaired health in the general population is 25% for all eight health concepts. Comparison between the eight health-concept variables is easy because the population norm is the same for each of them. These indicator variables are age and gender adjusted, so that even if the sample did not have the age and gender distribution as the general population, comparisons can still be made with the value of 25.

Behavior sequences of long-term care residents and their social partners

OBJECTIVES

This study examines similarities and differences in social interactions of residents of an assisted living facility and those of a nursing home. Given increasingly popular alternative models of long-term care such as assisted living, the study seeks to identify how these long-term care settings differentially promote dependence and independence among their residents.

METHODS

Data were collected during 256 observations of 64 residents and their social partners at meal times in public areas. Sequences of antecedent and response behaviors relating to independence and dependence in the two different long-term care settings were examined.

RESULTS

Social partners responded consistently to behavior of long-term care residents, and the behavior of residents was consistently affected by that of their social partners. These sequential interactions were not affected by setting.

DISCUSSION

Differences in the nursing home and assisted living facilities' stated philosophies of care were not manifested in the interactions of their staff and residents.

The translocation-associated tox1 locus of Cochliobolus heterostrophus is two genetic elements on two different chromosomes

Previously, Tox1 was defined as a single genetic element controlling the difference between races of Cochliobolus heterostrophus: race T is highly virulent on T-cytoplasm corn and produces the polyketide T-toxin; race O is weakly virulent and does not produce T-toxin. Here we report that Tox1 is two loci, Tox1A and Tox1B, on two different chromosomes. Evidence for two loci derives from: (1) the appearance of 25% Tox+ progeny in crosses between induced Tox1(-) mutants, one defective at Tox1A, the other at Tox1B; (2) the ability of Tox1A- + Tox1B- heterokaryons to complement for T-toxin production; and (3) electrophoretic karyotypes proving that Tox1(-) mutations are physically located on two different chromosomes. Data showing Tox1 as a single genetic element are reconciled with those proving it is two loci by the fact that Tox1 is inseparably linked to the breakpoints of a reciprocal translocation; the translocation results in a four-armed linkage group. In crosses where the translocation is heterozygous (i.e., race T by race O), all markers linked to the four-armed intersection appear linked to each other; in crosses between induced Tox1(-) mutants, complications due to the translocation are eliminated and the two loci segregate independently.

Evaluation of the bias in using the time to the first event when the inter-event intervals have a Weibull distribution

Currently the analysis of clinical trials for treatment of paroxysmal atrial fibrillation (PAF) relies on the assumption that the events are distributed according to a Poisson distribution. We contend that the occurrence of PAF events are clearly not Poisson and tend to occur in clusters. A candidate parametric model of the inter-event interval, the Weibull distribution, is presented. When the events are distributed according to a Poisson distribution, the time to the first event (TFE) has the same distribution as the inter-event intervals (IEI) due to the 'memoryless' property of the Poisson distribution, hence the TFE can be used instead of the IEI. When the events do not form a Poisson distribution, the TFE does not have the same distribution as the IEI. We show that for the Weibull distribution, when the TFE is used to model the IEI, both the mean and the survivor distribution are biased. The bias in the survivor function is a function both of time and the parameters of the distribution. Therefore when two groups have different parameters for their distributions (as in the case of different treatment effects), the discrepancy between the survivor distribution of the IEI and the survivor distribution of the TFE is affected differentially. We demonstrate the low coverage probabilities of the mean and the survivor function which result when the underlying distribution is Weibull with shape parameter kappa < 1.0. It is likely that this problem will arise for other clustered event processes. This suggests that careful empirical investigation of the distribution of IEI for recurrent events is necessary before choosing to analyse the data using the TFE.