Biomedical subjects

David T Redden

Publications and source records attributed to David T Redden.

26 records · Page 2Linked to original sources

PubMed2004

Statistical methods for testing effects on "maximum lifespan".

It has been noted that certain interventions such as caloric restriction may increase maximum lifespan, whereas other interventions may increase mean or median lifespan but not maximum lifespan. Here the term "maximum lifespan" is used to refer to the upper percentiles of the distribution of lifespan. This is of great interest because increasing maximum lifespan may be an indicator that an intervention is slowing the general process of aging and not merely retarding the development of specific diseases. However, formal methods for testing maximum lifespan have not been elucidated. Herein, we show via simulation that conditional t-test (CTT), a method that is sometimes used, is invalid. We then offer a new method based on quantile regression and we show that this method is, at worst, conservative and remains powerful and valid.

Animals↗

PubMed2003

Hierarchical linear models for the development of growth curves: an example with body mass index in overweight/obese adults.

When data are available on multiple individuals measured at multiple time points that may vary in number or inter-measurement interval, hierarchical linear models (HLM) may be an ideal option. The present paper offers an applied tutorial on the use of HLM for developing growth curves depicting natural changes over time. We illustrate these methods with an example of body mass index (BMI; kg/m(2)) among overweight and obese adults. We modelled among-person variation in BMI growth curves as a function of subjects' baseline characteristics. Specifically, growth curves were modelled with two-level observations, where the first level was each time point of measurement within each individual and the second level was each individual. Four longitudinal databases with measured weight and height met the inclusion criteria and were pooled for analysis: the Framingham Heart Study (FHS); the Multiple Risk Factor Intervention Trial (MRFIT); the National Health and Nutritional Examination Survey I (NHANES-I) and its follow-up study; and the Tecumseh Mortality Follow-up Study (TMFS). Results indicated that significant quadratic patterns of the BMI growth trajectory depend primarily upon a combination of age and baseline BMI. Specifically, BMI tends to increase with time for younger people with relatively moderate obesity (25 BMI <30) but decrease for older people regardless of degree of obesity. The gradients of these changes are inversely related to baseline BMI and do not substantially depend on gender.

Adult↗

PubMed2003

Years of life lost due to obesity.

CONTEXT: Public health officials and organizations have disseminated health messages regarding the dangers of obesity, but these have not produced the desired effect. OBJECTIVE: To estimate the expected number of years of life lost (YLL) due to overweight and obesity across the life span of an adult. DESIGN, SETTING, AND SUBJECTS: Data from the (1) US Life Tables (1999); (2) Third National Health and Nutrition Examination Survey (NHANES III; 1988-1994); and (3) First National Health and Nutrition Epidemiologic Follow-up Study (NHANES I and II; 1971-1992) and NHANES II Mortality Study (1976-1992) were used to derive YLL estimates for adults aged 18 to 85 years. Body mass index (BMI) integer-defined categories were used (ie, <17; 17 to <18; 18 to <19; 20 to <21; 21 to 45; or > or =45). A BMI of 24 was used as the reference category. MAIN OUTCOME MEASURE: The difference between the number of years of life expected if an individual were obese vs not obese, which was designated YLL. RESULTS: Marked race and sex differences were observed in estimated YLL. Among whites, a J- or U-shaped association was found between overweight or obesity and YLL. The optimal BMI (associated with the least YLL or greatest longevity) is approximately 23 to 25 for whites and 23 to 30 for blacks. For any given degree of overweight, younger adults generally had greater YLL than did older adults. The maximum YLL for white men aged 20 to 30 years with a severe level of obesity (BMI >45) is 13 and is 8 for white women. For men, this could represent a 22% reduction in expected remaining life span. Among black men and black women older than 60 years, overweight and moderate obesity were generally not associated with an increased YLL and only severe obesity resulted in YLL. However, blacks at younger ages with severe levels of obesity had a maximum YLL of 20 for men and 5 for women. CONCLUSION: Obesity appears to lessen life expectancy markedly, especially among younger adults.

Adult↗

PubMed2003

Urinary incontinence in the 12-month postpartum period.

OBJECTIVE: To describe the prevalence and severity of urinary incontinence in the 12-month postpartum period and to relate this incontinence to several potential risk factors including body mass index, smoking, oral contraceptives, breast-feeding, and pelvic floor muscle exercise. METHODS: Participants were 523 women, aged 14 to 42 years, who had obstetrical deliveries. The women were interviewed in their rooms on postpartum day 2 or 3 and by telephone 6 weeks, 3 months, 6 months, and 12 months postpartum. Chart abstraction was conducted to obtain obstetrical data from the index delivery. RESULTS: At 6 weeks postpartum, 11.36% of women reported some degree of urinary incontinence since the index delivery. Although the rate of incontinence did not change significantly over the postpartum year, frequency of accidents decreased over time. In the generalized estimating equation, postpartum incontinence was significantly associated with seven variables: baseline report of smoking (odds ratio [OR] 2.934; P =.002), incontinence during pregnancy (OR 2.002; P =.007), length of breast-feeding (OR 1.169; P =.023), vaginal delivery (OR 2.360; P =.002), use of forceps (OR 1.870; P =.024), and two time-varying covariates: frequency of urination (OR 1.123; P = <.001) and body mass index (OR 1.055; P =.005). Factors not associated with postpartum incontinence included age, race, education, episiotomy, number of vaginal deliveries, attendance at childbirth preparation classes, and performing pelvic floor muscle exercises during the postpartum period. CONCLUSION: Postpartum incontinence is associated with several risk factors, some of which are potentially modifiable and others that can help target at-risk women for early intervention.

Adolescent↗

PubMed2003

Nonreplication in genetic association studies of obesity and diabetes research.

The objective of this article is to provide an overview of the existing literature concerning the identification of genetic markers associated with obesity and diabetes. Specifically, this article will review recent association studies of diabetes and obesity with an emphasis on the need for the replication of findings. Unfortunately, a substantial number of the published associations between genetic markers and phenotypes, including diabetes and obesity, have not been replicated. Literature that addresses the potential reasons for the nonreplication of association studies (population stratification, publication bias, effect heterogeneity, Type I errors and lack of statistical power) is summarized. Recommendations to improve future association studies are presented.

Diabetes Mellitus↗

PubMed2003

Effects of heart isolation, voltage-sensitive dye, and electromechanical uncoupling agents on ventricular fibrillation.

We tested whether the interventions typically required for optical mapping affect activation patterns during ventricular fibrillation (VF). A 21 x 24 unipolar electrode array (1.5 mm spacing) was sutured to the left ventricular epicardium of 16 anesthetized pigs, and four episodes of electrically induced VF (30-s duration) were recorded. The hearts were then rapidly excised and connected to a Langendorff perfusion apparatus. Four of the hearts were controls, in which 24 additional VF episodes were then mapped. In the remaining 12 hearts, four VF episodes were mapped after isolation, four more episodes were mapped after exposure to the voltage-sensitive dye di-4-ANEPPS, and six more episodes were mapped after exposure to the electromechanical uncoupling agents diacetyl monoxime (DAM; 20 mmol/l, n = 6) or cytochalasin D (CytoD; 10 micromol/l, n = 6). VF episodes were separated by 4 min. VF activation patterns were quantified using custom pattern analysis algorithms. From comparisons with time-corrected control data, all interventions significantly changed VF patterns. Most changes were broadly consistent with slowing and regularization due to loss of excitability. Heart isolation had the largest effect on VF patterns, followed by CytoD, DAM, and dye.

Animals↗

PubMedDate not supplied

Improving processes of hospital care during the last hours of life.

BACKGROUND: Known for excellence in care in the last days and hours of life, hospice programs can help individuals have a "good death" and lead to higher family satisfaction with quality of care. Our objective was to evaluate the effectiveness of a multicomponent palliative care intervention based on the best practices of home hospice and designed to improve the quality of care provided for patients dying in an acute care inpatient setting. METHODS: This study was a before-after intervention trial conducted between 2001 and 2003. Participants included physician, nursing, and ancillary staff on inpatient services of an urban, tertiary care Veterans Affairs medical center. The palliative care intervention included staff education and support to identify patients who were actively dying and implement care plans guided by a comfort care order set template for the last days or hours of life. Data abstracted from computerized medical records of 203 veterans who died during a 6-month period before (n = 108) and after (n = 95) intervention were used to determine the impact of intervention on symptom documentation and 5 process of care indicators. RESULTS: There was a significant increase in the mean (SD) number of symptoms documented from 1.7 (2.1) to 4.4 (2.7) (P<.001), and the number of care plans increased from 0.4 (0.9) to 2.7 (2.3) (P<.001). Opioid medication availability increased from 57.1% to 83.2% (P<.001), and do-not-resuscitate orders increased from 61.9% to 85.1% (P<.001). There were nonsignificant changes in the proportion of deaths that occurred in intensive care units (P = .17) and in the use of nasogastric tubes (P = .40), and there was a significant increase in the use of restraints (P<.001). CONCLUSION: Our results indicate that end-of-life care improved after the introduction of the palliative care program.

Adult↗

PubMedDate not supplied

Association of early childbearing and low cognitive ability.

CONTEXT: Teenage pregnancy remains a pressing social issue and public health problem in the United States. Low cognitive ability is seldom studied as a risk factor for adolescent childbearing. METHODS: Data from the National Longitudinal Survey of Youth were used in a matched-pairs nested case-control study comparing women who had a first birth before age 18 with those who did not. Significant differences in Armed Forces Qualifications Test scores and in reproductive and social intervening variables were determined using chi-square analyses and t-tests. Multiple logistic regression models determined the independent effects of specific factors on early childbearing. RESULTS: Women who had their first birth before age 18 had significantly lower cognitive scores than others; women with a second birth before age 20 had significantly lower scores than those with one teenage birth. On average, women with the lowest cognitive scores initiated sexual activity 1.4 years earlier than those with the highest cognitive scores. Among those who had had a sexuality education course, a smaller proportion of women had scores in the first quartile for the overall sample than in the fourth quartile (20% vs. 28%); an even greater difference was seen among women who correctly answered a question about pregnancy risk (14% vs. 43%). Both poverty and low cognitive ability increased the odds of early childbearing. CONCLUSIONS: Young women with low cognitive ability are at increased risk for early initiation of sexual activity and early pregnancy. Further research is needed to design interventions that consider this population's specific information and support needs.

Adolescent↗