Biomedical subjects

Joel E Dimsdale

Publications and source records attributed to Joel E Dimsdale.

At least 19 recordsLinked to original sources

PubMed2007

Prediction of continuous positive airway pressure in obstructive sleep apnea.

Continuous positive airway pressure (CPAP) prediction formulas can potentially simplify the treatment of obstructive sleep apnea (OSA). However, they can be difficult to derive and validate. We tested a statistical method to derive and validate a CPAP prediction formula using the same sample population. Seventy-six OSA patients underwent polysomnography and CPAP titration. Anthropometric measures, sleep parameters, and the Epworth sleepiness scale (ESS) were evaluated as predictors. All subsets regression was used to determine the optimum number of variables in the model. The Bayes information criterion was used to find the best-fit model. The model was then evaluated by a tenfold cross-validation procedure. Subjects were obese (BMI 31.3 +/- 5.4) and had significant daytime somnolence (ESS 11.9 +/- 5). Mean respiratory disturbance index (RDI) was 53.5 +/- 31.3. The ESS was not predictive of titrated CPAP. The best-fit model included three variables (CPAP(pred) = 30.8 + RDI x 0.03 - nadir saturation x 0.05 - mean saturation x 0.2). This model explained 67% of the variance. Our data and the literature suggest that a combination of two to three factors is predictive of titrated CPAP: RDI, oxyhemoglobin saturation, and obesity. Except for RDI, the specific factors vary in each population. A CPAP prediction formula that explains a high proportion of the titrated CPAP variance can be easily derived from parameters measured during the diagnostic work-up of OSA patients using a unique statistical model that allows derivation and validation of the formula in the same test population.

Adult↗

PubMed2006

The association between fatigue and inflammatory marker levels in cancer patients: a quantitative review.

Increased cytokine and neopterin levels may be responsible for cancer-related fatigue, the most common complaint among cancer patients. We quantitatively reviewed empirical findings on this topic, focusing on studies not using immunotherapy. PubMed, PsychINFO and BIOSIS were searched for articles published until July 2006. Studies remained unweighted or were weighted according to study quality and sample size. The correlation coefficient r was used for statistical analyses. Heterogeneity among the studies was examined using the I(2) index. Eighteen studies (1037 participants) of moderately high methodological quality were located and statistically analyzed. Most studies measured more than one inflammatory marker, resulting in a total of 58 correlation estimates. In 31 of these, we had to input a null correlation because results had been simply reported as nonsignificant and no further statistical information was available. General analyses based on weighting according to sample size showed a significantly positive correlation between fatigue and circulating levels of inflammatory markers (r=0.11, p<0.0001). Analyses of individual inflammatory markers revealed significantly positive correlations between fatigue and IL-6 (r=0.12, p=0.004), fatigue and IL-1 ra (r=0.24, p=0.0005), and fatigue and neopterin (r=0.22, p=0.0001). Fatigue did not correlate significantly with IL-1 beta (r=0.05, p=0.42) or TNF-alpha (r=0.04, p=0.34). Given its preliminary nature due to the limited available data, this quantitative review showed a positive association between cancer-related fatigue and circulating levels of IL-6, IL-1 ra and neopterin. Future studies examining the relationship between cancer related fatigue and inflammation would benefit from multiple rather than single blood sampling and from repeated daily ratings of the multidimensional nature of fatigue.

Biomarkers↗

PubMed2006

Stress-related reduction in personal mastery is associated with reduced immune cell beta2-adrenergic receptor sensitivity.

BACKGROUND: A growing body of literature suggests that caregiving burden is associated with impaired immune system functioning, which may contribute to elevated morbidity and mortality risk among dementia caregivers. However, potential mechanisms linking these relationships are not well understood. The purpose of this study was to investigate whether stress-related experience of depressive symptoms and reductions in personal mastery were related to alterations in ss2-adrenergic receptor sensitivity. METHODS: Spousal Alzheimer's caregivers (N = 106) completed measures assessing the extent to which they felt overloaded by their caregiving responsibilities, experienced depressive symptoms, and believed their life circumstances were under their control. We hypothesized that caregivers reporting elevated stress would report increased depressive symptoms and reduced mastery, which in turn would be associated with reduced ss2- adrenergic receptor sensitivity on peripheral blood mononuclear cells (PBMC), as assessed by in vitro isoproterenol stimulation. RESULTS: Regression analyses indicated that overload was negatively associated with mastery (beta = -0.36, p = 0.001) and receptor sensitivity (beta = -0.24, p = 0.030), whereas mastery was positively associated with receptor sensitivity (beta = 0.29, p = 0.005). Finally, the relationship between overload and receptor sensitivity diminished upon simultaneous entry of mastery. Sobel's test confirmed that mastery significantly mediated some of the relationship between overload and receptor sensitivity (z = -2.02, p = 0.044). CONCLUSIONS: These results suggest that a reduced sense of mastery may help explain the association between caregiving burden and reduced immune cell ss2-receptor sensitivity.

Adaptation, Psychological↗

PubMed2006

Correlates of physical activity level in breast cancer survivors participating in the Women's Healthy Eating and Living (WHEL) Study.

BACKGROUND: Physical activity levels among breast cancer survivors are typically low, and knowledge of the correlates of increased physical activity among cancer survivors is limited. The purpose of this study was to examine factors that are associated with physical activity or inactivity among breast cancer survivors. METHODS: Data from 3088 women participating in the Women's Healthy Eating and Living (WHEL) Study, collected prior to randomization, were the focus of the current analyses. Self-reports of physical activity levels, quality of life, depression, and dietary intakes were collected. Pearson correlation analyses were employed to examine the associations among these variables, and multiple regression analyses were performed to examine the relationship between selected health behaviors and physical activity levels, after controlling for demographic, breast cancer-related, and psychosocial variables. RESULTS: Demographic and psychosocial variables were related to physical activity levels (P < 0.001 for all). Cancer treatment type and cancer stage were correlated with survivors' physical activity levels (P < 0.01), but the associations were no longer significant after controlling for demographic variables. Physical activity levels were strongly associated with other health behaviors, especially dietary intakes (P < 0.001), even after controlling for demographic, cancer-related, and psychosocial factors. CONCLUSION: Low physical activity levels in breast cancer survivors are associated with specific behavioral and other factors, which can be considered as indicators of women at higher risk. Findings of significant differences in physical activity levels based on demographic characteristics suggest the importance of promoting physical activity particularly among breast cancer survivors of ethnic minority or lower education levels.

Breast Neoplasms↗

PubMed2006

Comparison of the effects of depressive symptoms and apnea severity on fatigue in patients with obstructive sleep apnea: a replication study.

BACKGROUND: Links between fatigue and depressive symptoms in medically ill patients are well-documented; however, few studies controlled for illness severity. Obstructive sleep apnea (OSA) is a common, frequently devastating disease that often includes daytime sleepiness and fatigue. Fatigue is also a hallmark depressive symptom. We previously reported that depressive symptoms explained ten times the variance in fatigue in OSA patients as did OSA severity itself (respiratory disturbance index, oxyhemoglobin saturation). OSA severity explained 4.2% of variance in fatigue while depressive symptoms explained an additional 42.3%. Here, we report a replication of these findings in a new, independent sample. METHODS: 56 untreated OSA patients had their sleep monitored with polysomnography on the UCSD GCRC. Participants completed the Center for Epidemiologic Studies-Depression (CESD), Profile of Mood States (POMS) and Medical Outcomes Studies (MOS) surveys. Data were analyzed using hierarchical linear regression. RESULTS: OSA severity explained 13.4% (p=0.022) of variance in POMS fatigue while CESD scores explained an additional 24.5% (p<0.001). Results were robust to changes in the scales used to measure these constructs. LIMITATIONS: Cross-sectional design precludes determination of direction of causality. Assessment of depressive symptoms and fatigue was based on validated self-report measures. CONCLUSIONS: These results reaffirm that depressive symptoms are dramatically and independently associated with worse fatigue in OSA patients. While the independent contribution of OSA severity varied between studies, depressive symptoms were the strongest predictor of fatigue in both studies. Assessment and treatment of mood symptoms-not just treatment of OSA itself-might reduce fatigue in these patients.

Adult↗

PubMed2006

Physical fitness attenuates leukocyte-endothelial adhesion in response to acute exercise.

Studies suggest that physical fitness promotes cardiovascular health, including improved endothelial function and possibly reduced inflammatory responses to stressors. This study examined the effects of fitness on leukocyte-endothelial adhesion in response to an acute exercise challenge. Peripheral blood mononuclear cell (PBMC) adhesion to human umbilical venous endothelial cells (HUVEC) was examined in 18 more-fit and 19 less-fit individuals [mean age 39 yr (SD 11)] before and after a 20-min treadmill exercise at 65-70% peak oxygen consumption. PBMC were isolated from whole blood (Ficoll-Paque) at rest and immediately after exercise. HUVEC were incubated for 4 h in the presence of cytokines IL-1 and IL-8 to activate endothelial adhesion molecule expression. Fit subjects showed a significant reduction in PBMC-HUVEC adhesion after exercise (P < 0.01) compared with less-fit subjects, who showed no significant change. Regardless of fitness levels, both at rest and in response to exercise, soluble ICAM-1 in the incubation media attenuated PBMC-HUVEC adhesion by approximately 81% (P < 0.001). The findings indicate that immune cells that demarginate in response to exercise have reduced ability to adhere in individuals who are physically fit, an effect apparently independent of ICAM-1 binding. The findings provide evidence of how physical fitness might protect individuals from inflammatory responses to exercise.

Adaptation, Physiological↗

PubMed2006

Objective cancer-related variables are not associated with depressive symptoms in women treated for early-stage breast cancer.

PURPOSE: Women with breast cancer are thought to be vulnerable to depression for reasons associated with impact of diagnosis, treatment, and metabolic/endocrine changes. While the literature shows that most of these women do not become clinically depressed, 15% to 30% report elevated depressive symptoms that may be clinically important. The purpose was to identify and determine the relative importance of predictors of depressive symptoms in women treated for early-stage breast cancer. PATIENTS AND METHODS: A total of 2,595 women (< or = 4 years following completion of initial treatment for early-stage breast cancer) provided data on cancer-related variables, personal characteristics, health behaviors, physical functioning/symptoms, and psychosocial variables. Participants were divided into high or low depressive groups using the Center for Epidemiologic Studies Depression Scale screening form. RESULTS: Results of the binary logistic regression analysis were significant (overall R2 = 32.4%). Before entry of psychosocial variables, younger age, being unmarried, poorer physical functioning, and more vasomotor and gastrointestinal symptoms were significant risk factors for elevated depressive symptoms (R2 = 16.1%), but objective cancer-related variables were not. After inclusion of psychosocial variables in the model (DeltaR2 = 16.3%), none of the preceding variables remained significant. Greater risk for depressive symptoms was associated with stressful life events, less optimism, ambivalence over expressing negative emotions, sleep disturbance, and poorer social functioning. CONCLUSION: Depressive symptoms in women treated for early-stage breast cancer are not associated with objective cancer-related factors. Rather, they are most strongly linked with many subjective psychosocial variables.

Adult↗

PubMed2006

Effects of continuous positive airway pressure versus supplemental oxygen on 24-hour ambulatory blood pressure.

Obstructive sleep apnea (OSA) is associated with recurrent episodes of nocturnal hypoxia and increased risk for development of systemic hypertension. Prior studies have been limited, however, in their ability to show reduction in blood pressure after continuous positive airway pressure (CPAP) therapy, and the effect of supplemental oxygen alone on blood pressure in OSA has not been evaluated. We performed a randomized, double-blind, placebo-controlled study comparing the effects of 2 weeks of CPAP versus sham-CPAP versus supplemental nocturnal oxygen on 24-hour ambulatory blood pressure in 46 patients with moderate-severe OSA. We found that 2 weeks of CPAP therapy resulted in a significant reduction in daytime mean arterial and diastolic blood pressure and nighttime systolic, mean, and diastolic blood pressure (all Ps <0.05). Although nocturnal supplemental oxygen therapy improved oxyhemoglobin saturation, it did not affect blood pressure. We conclude that CPAP therapy reduces both daytime and nighttime blood pressure in patients with OSA, perhaps through mechanisms other than improvement of nocturnal oxyhemoglobin saturation.

Adult↗

PubMed2006

Association between sleep apnea severity and blood coagulability: Treatment effects of nasal continuous positive airway pressure.

A prothrombotic state may contribute to the elevated cardiovascular risk in patients with obstructive sleep apnea (OSA). We investigated the relationship between apnea severity and hemostasis factors and effect of continuous positive airway pressure (CPAP) treatment on hemostatic activity. We performed full overnight polysomnography in 44 OSA patients (mean age 47+/-10 years), yielding apnea-hypopnea index (AHI) and mean nighttime oxyhemoglobin saturation (SpO2) as indices of apnea severity. For treatment, subjects were double-blind randomized to 2 weeks of either therapeutic CPAP (n = 18), 3 l/min supplemental nocturnal oxygen (n = 16) or placebo-CPAP (<1 cm H2O) (n = 10). Levels of von Willebrand factor antigen (VWF:Ag), soluble tissue factor (sTF), D-dimer, and plasminogen activator inhibitor (PAI)-1 antigen were measured in plasma pre- and posttreatment. Before treatment, PAI-1 was significantly correlated with AHI (r = 0.47, p = 0.001) and mean nighttime SpO2 (r = -0.32, p = 0.035), but these OSA measures were not significantly related with VWF:Ag, sTF, and D-dimer. AHI was a significant predictor of PAI-1 (R2 = 0.219, standardized beta = 0.47, p = 0.001), independent of mean nighttime SpO2, body mass index (BMI), and age. A weak time-by-treatment interaction for PAI-1 was observed (p = 0.041), even after adjusting for age, BMI, pre-treatment AHI, and mean SpO2 (p = 0.046). Post hoc analyses suggested that only CPAP treatment was associated with a decrease in PAI-1 (p = 0.039); there were no changes in VWF:Ag, sTF, and D-dimer associated with treatment with placebo-CPAP or with nocturnal oxygen. Apnea severity may be associated with impairment in the fibrinolytic capacity. To the extent that our sample size was limited, the observation that CPAP treatment led to a decrease in PAI-1 in OSA must be regarded as tentative.

Adult↗

PubMed2006

Does obstructive sleep apnea increase hematocrit?

This study assessed the relationship between hematocrit levels and severity of obstructive sleep apnea (OSA) and examined how this relationship was affected by the degree of hypoxia as well as by possible confounding factors. Two-hundred sixty three subjects (189 men and 74 women) underwent nocturnal polysomnography with oximetry and had measurements of hematocrit, hemoglobin, white blood cell count, body mass index (BMI), blood pressure (BP), and 24-h urine norepinephrine (NE). Patients with severe OSA [respiratory disturbance index (RDI) >30] had significantly higher hematocrit values than patients with mild to moderate OSA or nonapneic controls (p < 0.01). However, only one patient had a hematocrit in the range of clinical polycythemia. Hematocrit levels were significantly correlated with BMI, BP, urinary NE, RDI, percent of time spent at oxygen saturation <90%, and with mean oxygen saturation. Multiple linear regression analysis revealed that mean oxygen saturation, RDI, and percent of time spent at oxygen saturation <90% were significant predictors of hematocrit level, even after controlling for gender, ethnicity, 24-h urine NE, BMI, and BP (p < 0.05). The severity of OSA is significantly associated with increased hematocrit, even after controlling for possible confounding variables. However, nocturnal hypoxemia in OSA does not usually lead to clinical polycythemia.

Adult↗

PubMed2006

The toll of ethnic discrimination on sleep architecture and fatigue.

Most work on ethnicity tends to focus on daytime health rather than how aspects of ethnicity affect nighttime functioning. The current study examined how discrimination and ethnic identity relate to sleep architecture and fatigue in 37 African Americans and 56 Caucasian Americans. The authors conducted sleep monitoring with standard polysomnography. African Americans had less slow-wave sleep and reported more physical fatigue than did Caucasian Americans (ps < .05). The authors conducted path analyses to examine relationships between ethnic identity, perceived discrimination, sleep, and fatigue. Perceived discrimination mediated ethnic differences in Stage 4 sleep and physical fatigue. Individuals who reported experiencing more discrimination had less Stage 4 sleep and reported experiencing greater physical fatigue (ps < .05). Although ethnic identity did not mediate ethnic differences in sleep latency, there was a significant relationship between ethnic identity and sleep latency, indicating that individuals who felt more connected to their ethnic group had more difficulty falling asleep while in the hospital (p < .05). These observations suggest that the effects of stress related to one's ethnic group membership carry over into sleep.

Adult↗

PubMed2006

Effect of Alzheimer caregiving stress and age on frailty markers interleukin-6, C-reactive protein, and D-dimer.

BACKGROUND: Elevated plasma levels of interleukin (IL)-6, C-reactive protein (CRP), and D-dimer belong to the biological alterations of the "frailty syndrome," defining increased vulnerability for diseases and mortality with aging. We hypothesized that, compatible with premature frailty, chronic stress and age are related in predicting inflammation and coagulation activity in Alzheimer caregivers. METHODS: Plasma IL-6, CRP, and D-dimer levels were measured in 170 individuals (mean age 73 +/- 9 years; 116 caregivers, 54 noncaregiving controls). Demographic factors, diseases, drugs, and lifestyle variables potentially affecting inflammation and coagulation were obtained by history and adjusted for as covariates in statistical analyses. RESULTS: Caregivers had higher mean levels of IL-6 (1.38 +/- 1.42 vs 1.00 +/- 0.92 pg/mL, p =.032) and of D-dimer (723 +/- 530 vs 471 +/- 211 ng/mL, p <.001) than controls had. CRP levels were similar between groups (p =.44). The relationship between caregiver status and D-dimer was independent of covariates (p =.037) but affected by role overload. Age accounted for much of the relationship with IL-6. After controlling for covariates, the interaction between caregiver status and age was significant for D-dimer (beta =.20, p =.029) and of borderline significance for IL-6 (beta =.17, p =.090). Post hoc regression analyses indicated that, among caregivers, age was significantly correlated with both D-dimer (beta =.50, p <.001) and IL-6 (beta =.38, p =.001). Among controls, however, no significant relationship was observed between age and either D-dimer or IL-6. CONCLUSIONS: The interaction between caregiving status and age for D-dimer and IL-6 suggests the possibility that older caregivers could be at risk of a more rapid transition to the frailty syndrome and clinical manifestations of cardiovascular diseases.

Age Factors↗

PubMed2006

Sleep disturbance, norepinephrine, and D-dimer are all related in elderly caregivers of people with Alzheimer disease.

STUDY OBJECTIVE: Caregiving for a relative with Alzheimer disease has been associated with sympathoadrenal medullary arousal and morbidity and mortality. In this study, we examined if sleep disturbance of elderly caregivers was associated with physiologic markers of cardiovascular risk, including plasma norepinephrine, epinephrine, and the hemostasis marker D-dimer. DESIGN: Cross-sectional. SETTING: Community-based sample of elderly caregivers of spouses with Alzheimer disease assessed within their homes. PARTICIPANTS: A sample of 40 elderly spousal caregivers of patients with Alzheimer disease. MEASUREMENTS AND RESULTS: Participants underwent in-home full-night polysomnography and had plasma assayed for norepinephrine and epinephrine. Using multiple regression analyses and controlling for a number of cardiovascular risk factors (e.g., age, sex, blood pressure, body mass index), increased wake after sleep onset was positively associated with norepinephrine levels (beta = .35; t = 2.45, df = 32, p = .020) and plasma D-dimer (beta = .31; t = 2.18, df = 29, p = .038). Further, plasma norepinephrine was significantly associated with D-dimer (beta = .34; t = 2.11, df = 29, p = .044). Additional analyses indicated that norepinephrine accounted for 28% of the relationship between wake after sleep onset and D-dimer. No association was observed between sleep variables and epinephrine. CONCLUSIONS: These findings provide preliminary evidence that sleep disturbance may contribute to morbidity in caregivers through sympathoadrenal medullary arousal and downstream physiologic effects such as altering the hemostasis environment.

Aged↗

PubMed2006

Effect of continuous positive airway pressure versus supplemental oxygen on sleep quality in obstructive sleep apnea: a placebo-CPAP-controlled study.

STUDY OBJECTIVE: We investigated the short-term effectiveness of continuous positive airway pressure (CPAP) and oxygen in improving sleep quality in patients with obstructive sleep apnea (OSA). DESIGN: Randomized, double-blind, placebo-controlled, parallel study. SETTING: General Clinical Research Center at a university hospital. PATIENTS: Seventy-six patients with untreated OSA. INTERVENTIONS: Patients were randomly assigned to 1 of 3 treatments (CPAP, placebo-CPAP, or nocturnal oxygen at 3 L per minute) for 2 weeks. Sleep quality was assessed at baseline and after 1 and 14 days of therapy. Repeated-measures analysis of variance was used to evaluate treatment and time effects, and their interaction. MEASUREMENTS AND RESULTS: Sixty-three patients completed the protocol. When compared with placebo-CPAP and nocturnal oxygen, CPAP increased rapid eye movement (REM) sleep and significantly reduced stage 1 sleep and the number of stage shifts (p < or = .003). CPAP improved, to within normal limits, the apnea-hypopnea index, total arousal index, and mean oxyhemoglobin saturation (p < or = .001). The effects of CPAP were apparent during the first night of therapy. Oxygen improved only mean nocturnal saturation (p = .009). CPAP had no significant effect on stage 2 sleep or slow-wave sleep. CONCLUSIONS: CPAP was associated with an improvement in sleep quality in patients with OSA by consolidating sleep, reducing stage 1 sleep, and improving REM sleep. CPAP was effective in correcting the respiratory and arousal abnormalities of OSA. The effectiveness of supplemental oxygen was limited to oxyhemoglobin desaturation.

Arousal↗

PubMed2006

Avoidant coping partially mediates the relationship between patient problem behaviors and depressive symptoms in spousal Alzheimer caregivers.

OBJECTIVE: Caring for a loved one with Alzheimer disease is a highly stressful experience that is associated with significant depressive symptoms. Previous studies indicate a positive association between problem behaviors in patients with Alzheimer disease (e.g., repeating questions, restlessness, and agitation) and depressive symptoms in their caregivers. Moreover, the extant literature indicates a robust negative relationship between escape-avoidance coping (i.e., avoiding people, wishing the situation would go away) and psychiatric well-being. The purpose of this study was to test a mediational model of the associations between patient problem behaviors, escape-avoidance coping, and depressive symptoms in Alzheimer caregivers. METHODS: Ninety-five spousal caregivers (mean age: 72 years) completed measures assessing their loved ones' frequency of problem behaviors, escape-avoidance coping, and depressive symptoms. A mediational model was tested to determine if escape-avoidant coping partially mediated the relationship between patient problem behaviors and caregiver depressive symptoms. RESULTS: Patient problem behaviors were positively associated with escape-avoidance coping (beta = 0.38, p < 0.01) and depressive symptoms (beta = 0.26, p < 0.05). Escape-avoidance coping was positively associated with depressive symptoms (beta = 0.33, p < 0.01). In a final regression analysis, the impact of problem behaviors on depressive symptoms was less after controlling for escape-avoidance coping. Sobel's test confirmed that escape-avoidance coping significantly mediated the relationship between problem behaviors and depressive symptoms (z = 2.07, p < 0.05). CONCLUSION: Escape-avoidance coping partially mediates the association between patient problem behaviors and depressive symptoms among elderly caregivers of spouses with dementia. This finding provides a specific target for psychosocial interventions for caregivers.

Adaptation, Psychological↗

PubMed2006

Dementia severity of the care receiver predicts procoagulant response in Alzheimer caregivers.

BACKGROUND: The procoagulant factor D-dimer has been shown to be associated with thrombus formation and degradation as seen with conditions such as myocardial infarction and unstable angina. Research has demonstrated that spousal dementia caregivers have elevated levels of D-dimer relative to their non-caregiving peers. OBJECTIVE: The objective of this study was to determine the relationship of basal level and laboratory stressor-induced concentration of D-dimer to severity of dementia in spousal care recipients. METHODS: Seventy-one elderly caregivers were compared with a comparison group of 37 non-caregivers (average age: 71 years). Clinical Dementia Rating (CDR), a global measure of dementia, was used to assess severity of spousal dementia. Plasma D-dimer was measured at baseline and in response to an acute speech stressor. RESULTS: Regression analysis revealed a significant positive association between severity of spousal dementia and caregiver D-dimer, both at baseline and in response to acute stress, while controlling for age. The model examined an exponential relationship, with D-dimer increasing progressively across the span of dementia stages. DISCUSSION: Dementia severity of the care recipient was associated with increasing hypercoagulability among elderly caregivers. Effect size estimates suggest that such D-dimer increases may have clinical implications, particularly among late-stage caregivers.

Aged↗

PubMed2006

Personal mastery attenuates the effect of caregiving stress on psychiatric morbidity.

This study examined the protective effects of personal mastery on the relations between both objective and subjective stress and psychiatric morbidity in 79 spousal Alzheimer caregivers. Results indicated that with low mastery, the relations between patient problem behaviors and caregiver psychiatric symptoms was significant (t[71] = 2.03; p = 0.046). However, with high mastery, no significant association was found (t[71] = -0.76; p = 0.452). Similarly, the relations between role overload and psychiatric morbidity was significant when mastery was low (t[71] = 2.22; p = 0.029), but not high (t[71] = -1.49; p = 0.140). These results suggest that caregivers with a greater sense of personal mastery may be protected from the negative effects of caregiver stress.

Caregivers↗

PubMed2006

Assessing the trade-offs between crossover and parallel group designs in sleep research.

Sleep researchers invariably struggle with decisions regarding the optimal design for their studies. Whether such studies involve treatment for insomnia, obstructive sleep apnea, or any other sleep disorder, questions arise regarding the respective trade-offs between a parallel group and a crossover design. This study analyzed the variance structure of commonly measured polysomnographic variables in an effort to describe the statistical impact of these alternate designs. The study examined the effects of opioids on sleep and employed multiple crossovers between placebo, MS-contin, and methadone using a double-blind, randomized crossover design. Thirty-seven healthy subjects were studied. Four of the subjects were unable to complete the protocol for a variety of reasons, and polysomnogram data was unavailable for one subject. Data from 37 subjects provide the basis for this analysis. Despite dropouts, the crossover study was approximately four times as efficient as the parallel group design in terms of being able to recognize differences in deep sleep across these conditions. Other polysomnographic variables also favored the crossover design to varying extents. Despite the operational complexity of a crossover design, the statistical efficiency of this approach makes it a preferable approach for designing intervention studies in sleep research.

Adult↗