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Biomedical subjects

M Palta

Publications and source records attributed to M Palta.

At least 37 records · Page 2Linked to original sources
PubMed1998

Blood pressure perturbations caused by subclinical sleep-disordered breathing.

We studied the acute effects of apneas and hypopneas on blood pressure in a nonclinic population of middle-aged adults. Arterial pressure was measured noninvasively (photoelectric plethysmography) during an overnight, in-laboratory polysomnographic study in 72 men and 23 women enrolled in the Wisconsin Sleep Cohort Study, a population-based study of sleep-disordered breathing. Sleep-disordered breathing events (272 apneas and 1469 hypopneas) were observed in 92% of subjects. The across-subject mean decreases in arterial O2 saturation were 9+/-8% (SD) for apneas (17+/-8 seconds duration) and 4+/-3% for hypopneas (21+/-6 seconds duration; 41+/-17% of baseline ventilation). In both apneas and hypopneas, even those with only 1% to 3% O2 desaturations, blood pressure decreased during the event, followed by an abrupt increase in the postevent recovery period. Mean values for peak changes in blood pressure (difference between the maximum during the recovery period and the minimum during the event) were 23+/-10 mm Hg for systolic and 13+/-6 mm Hg for diastolic pressure. The strongest predictors of the pressor responses to apneas and hypopneas were (in order of importance): magnitude of the ventilatory overshoot, length of the event, magnitude of changes in heart rate and arterial O2 saturation, and presence or absence of electroencephalographic arousal. We speculate that these fluctuations may play a role in the pathogenesis of hypertension in individuals with subclinical sleep-disordered breathing.

Cohort Studies↗
PubMed1998

Sleep-disordered breathing and self-reported general health status in the Wisconsin Sleep Cohort Study.

OBJECTIVE: To determine the relationship between sleep-disordered breathing and self-reported general health status. breathing status assessed by overnight in-laboratory polysomnography. SETTING: General Community. SUBJECTS: Employed men (n=421) and women (n=316), ages 30-60 years, enrolled in the Wisconsin Sleep Cohort Study. INTERVENTIONS: None. OUTCOME MEASURE: Self-reported general health profile and life satisfaction measured by the Medical Outcomes Survey Short Form-36 and obtained by interview. RESULTS: Sleep-disordered breathing was associated with lower general health status before and after adjustment for age, sex, body mass index, smoking status, alcohol usage, and a history of cardiovascular conditions. Even mild sleep-disordered breathing (apnea-hypopnea index = 5) was associated with decrements in the Medical Outcomes Short Form 36 Survey health constructs comparable to the magnitude of decrements linked to other chronic conditions such as arthritis, angina, hypertension, diabetes, and back problems. CONCLUSIONS: Sleep-disordered breathing is independently related to lower general health status, and this relationship is of clinical significance. Given the growing emphasis of the importance of patients' perceptions of health, these findings are relevant to estimating the overall impact of sleep-disordered breathing.

Adult↗
PubMed1998

Associations between family history of asthma, bronchopulmonary dysplasia, and childhood asthma in very low birth weight children.

Very low birth weight (VLBW) infants are at risk for childhood wheezing and asthma, as are children with a family history of asthma. Family history of asthma may also be associated with premature labor and, among VLBW infants, with bronchopulmonary dysplasia (BPD) and chronic lung disease (CLD) of prematurity. This study targeted all neonates with birth weight <1,501 g who were admitted to seven perinatal centers in Wisconsin and Iowa between August 1, 1988 and June 30, 1991. Comprehensive information was collected for 723 of the 1,007 30-day survivors, and for 106 full-term controls. A representative subgroup of 257 VLBW children was contacted at age 5 years to ascertain bronchodilator and/or steroid use and diagnosis of asthma. Some evidence of an association between family history of asthma and premature birth was found, but it was not associated with neonatal BPD/CLD or BPD/CLD severity. Among BPD/CLD indicators, radiographic evidence of BPD at age 25-35 days was most strongly associated with bronchodilator use up to age 2 years (odds ratio (OR) = 10.1, 95% confidence interval (CI) 4.07-25.2) and with asthma between ages 2 years and 5 years (OR = 4.83, 95% CI 2.18-10.7). Among children without radiographic evidence of BPD, family history of asthma was associated with childhood asthma and bronchodilator use.

Asthma↗
PubMed1998

Associations between antioxidant and zinc intake and the 5-year incidence of early age-related maculopathy in the Beaver Dam Eye Study.

Associations between antioxidants and zinc and the 5-year incidence of early, age-related maculopathy (ARM) were investigated in a population-based cohort of middle-aged and older adults participating in the Beaver Dam Eye Study in Beaver Dam, Wisconsin. A food-frequency questionnaire was administered at baseline (1988-1990) to collect dietary information for that time period and a period of time 10 years earlier (1978-1980) from a 50 percent random sample of persons participating in this study. The incidence of the specific lesions of larger drusen (>125 microns) and pigmentary abnormalities and the incidence of any ARM were assessed by masked grading of stereoscopic color fundus photographs in 1,709 persons who participated in 5-year follow-up eye examinations. Significant, but modest, inverse associations (p < 0.05) were observed between intakes of pro-vitamin A carotenoids and dietary vitamin E and the incidence of large drusen and between zinc and the incidence of pigmentary abnormalities. No significant inverse associations were found between antioxidant or zinc intake and the incidence of overall early ARM. If ARM, which is characterized by a broad spectrum of lesions, involves a number of different underlying pathophysiologic processes, then associations between specific antioxidants and the incidence of distinct macular lesions may be biologically important. However, because there were too few incident late ARM cases in this cohort, the authors were unable to assess whether antioxidant intake is associated with the progression of early ARM to late-stage macular degeneration. Clinical trials and longer-term prospective studies are needed to elucidate further the impact of antioxidants and zinc on the development and progression of ARM.

Adult↗
PubMed1998

Evaluation of criteria for chronic lung disease in surviving very low birth weight infants. Newborn Lung Project.

Criteria in common use for the diagnosis of chronic lung disease of prematurity or bronchopulmonary dysplasia in the neonatal period have not been sufficiently compared and validated against indicators of later respiratory complications. In this study of all 680 infants < or = 1500 gm birth weight admitted to six perinatal centers August 1, 1988, to July 31, 1990, 524 were alive and had no major congenital anomalies at 5 years old. Of 419 who had given permission to release their names and addresses, 272 were located and participated in a follow-up study. The following diagnostic criteria for bronchopulmonary dysplasia and chronic lung disease of prematurity were used during the initial hospitalization: (1) use of supplemental oxygen on day 30 of life, (2) a comprehensive bronchopulmonary dysplasia severity score applied at 25 to 35 days of life developed by a clinician panel to adjust for practice variation in ventilatory support and blood gases, (3) use of supplemental oxygen on day 30 of life with radiographic evidence consistent with bronchopulmonary dysplasia between days 25 and 35 of life, (4) radiographic evidence consistent with bronchopulmonary dysplasia alone, and (5) use of supplemental oxygen at 36 weeks' postconceptional age. These criteria were assessed against use of bronchodilators or steroids during the first 2 years of life, diagnosis of asthma, and hospitalizations for respiratory causes up to age 5. Although all criteria were significantly associated with all the outcomes, radiographic evidence was most predictive. These results indicate that, during a period when 21% of neonates were exposed to antenatal steroids, 24% received surfactant and 9% received postnatal corticosteroids, radiographic evidence was more predictive of long-term respiratory outcome than other commonly used criteria.

Bronchopulmonary Dysplasia↗
PubMed1998

Association of tocolytic therapy with antenatal steroid administration and infant outcomes. Newborn Lung Project.

The use of tocolytic agents to halt premature labor is controversial. We examine a database on very low-birth-weight infants born following the onset of premature labor (n = 540) for association between tocolytic and antenatal steroid therapy, and to assess neonatal and childhood outcomes following combined therapy. Data are from a multicenter regionally based study of all infants below 1501 g at seven neonatal intensive care units (NICUs) in Wisconsin and Iowa, born August 1, 1988 through June 30, 1991. Infant outcomes analyzed are death in the first 30 days, respiratory distress syndrome (RDS), and intraventricular hemorrhage (IVH). Fewer deliveries occurred within 12 hours of labor onset with tocolytics (61 vs. 75% without). A strong association between tocolytic therapy and antenatal steroid administration was found [adjusted odds ratio OR = 5.7, 95% confidence interval CI: (3.3, 10.0)]. Tocolytics were associated with lower mortality in the first 30 days [OR = 0.29, CI: (0.15, 0.56)]. Joint administration of tocolytics and antenatal steroids versus neither was associated with lower incidence of the combined outcome of respiratory distress syndrome (RDS) or death [OR = .30, CI: (0.15, 0.60)] and grade III-IV IVH or death [OR = 0.35, CI: (0.14, 0.98)]. Tocolytic therapy alone was not associated with IVH grade III-IV [OR = 1.0, CI: (0.57, 1.9)] among survivors.

Cerebral Hemorrhage↗
PubMed1998

Differentiation of acute cortical and subcortical ischemic stroke by risk factors and clinical examination findings.

BACKGROUND: Differentiation between acute cortical and subcortical ischemic stroke may be problematic when cortical stroke presents without obvious cortical deficits such as aphasia, neglect or hemianopia. This study explores stroke risk factors and clinical variables that may assist in this differentiation. METHODS: Records of consecutive patients with acute ischemic stroke, examined within 72 h of symptom onset, were reviewed. Stroke type was verified by clinical course and follow-up imaging. Stroke risk factors and acute examination findings were compared by odds ratios and positive predictive values for cortical and subcortical stroke. RESULTS: For 355 patients studied, 237 had cortical stroke and 118 had subcortical stroke. Odds ratios for cortical stroke were highest for atrial fibrillation by EKG (OR = 4.77, CI = 2.08-10.94), recent hospitalization (OR = 4.51, CI = 2.39-8.53) and nonalert mental status (OR = 4.50, CI = 2.29-8.87). Possible cardioembolic condition, ischemic heart disease and peripheral vascular disease were also significant, but hypertension, age and diabetes mellitus were not significantly different for the stroke subtypes. Cortical deficits were absent in 19.4% of cortical stroke patients on initial examination. Predictive models were generated based on the presence or absence of cortical deficits and the interaction of significant risk factors with degree of motor deficit. CONCLUSIONS: There are clinical features that, in addition to initial examination, may help differentiate cortical from subcortical ischemic stroke. These features may be relevant to both diagnostic and therapeutic approaches to acute stroke.

Acute Disease↗
PubMed1997

Risk factors for hospitalization in a cohort with type 1 diabetes. Wisconsin Diabetes Registry.

The authors investigate the postonset hospitalization rate and risk factors during 1987-1994 in Wisconsin, in a population-based, incidence cohort followed from diagnosis of Type 1 diabetes mellitus at ages 0-29 (n = 577). The overall rate was 8.9 +/- 0.60 (standard error) per 100 person-years of diabetes, whereof 5.7 was due to hyperglycemia, 1.9 to hypoglycemia, and 1.3 to other and undetermined causes. Major risk factors for hospitalization were longitudinally measured glycosylated hemoglobin level (rate ratio = 1.5 per 2% increase, 95% confidence interval 1.4-1.7), black/other race (rate ratio = 1.9, 95% confidence interval 1.0-3.6), diagnosis in a non-university-based setting (rate ratio = 1.9, 95% confidence interval 1.2-3.2), female sex (rate ratio = 1.5, 95% confidence interval 1.0-2.4 at age 11), age in males (rate ratio = 0.6, 95% confidence interval 0.4-0.8 per 5-year increase), and public or no insurance up to 18 months postdiagnosis (rate ratio = 2.2, 95% confidence interval 1.1-4.4). For individuals less than 18 years, "black/other race" was replaced in the model by "having other than two biologic parents in the home" (rate ratio = 2.0, 95% confidence interval 1.1-3.5). Hence, hospitalization is common in children, adolescents, and young adults with diabetes, primarily for problems with glycemic control.

Adolescent↗
PubMed1997

Incidence of retinopathy and associated risk factors from time of diagnosis of insulin-dependent diabetes.

OBJECTIVE: To describe the prevalence at baseline and 4-year incidence of retinopathy and its relation to glycemic control from the time of diagnosis of insulin-dependent diabetes. DESIGN: Geographically defined population-based study. SETTING: Twenty-eight-county area in Wisconsin. STUDY POPULATION: Incipient cohort of children, teenagers, and young adults (n = 354) up to 30 years of age with newly diagnosed insulin-dependent diabetes. MAIN OUTCOME MEASURE: Diabetic retinopathy as determined by gradings from 30 degrees color stereoscopic photographs of the Diabetic Retinopathy Study 7 standard fields. RESULTS: The prevalence of retinopathy at diagnosis was 1.3%. Four years after diagnosis of diabetes, retinopathy was first identified in 5.1% of our cohort and in 9.7% of those 15 years of age or older. After controlling for age, subjects with a mean glycosylated hemoglobin level of 12% or greater were 3.2 times as likely (95% confidence interval, 1.1-9.9) to have retinopathy present at follow-up as were subjects with a mean glycosylated hemoglobin level of less than 12%. CONCLUSION: Population-based data on the frequency and incidence of retinopathy from the time of diagnosis of insulin-dependent diabetes mellitus provided by this study suggest a possible reduction in risk of developing retinopathy in those in whom glycemic control is achieved from the time of diagnosis.

Adolescent↗
PubMed1997

Incorporating fat-modified foods into a food frequency questionnaire improves classification of fat intake.

OBJECTIVE: To determine the extent to which incorporating fat-modified foods into a food frequency questionnaire influences the agreement of energy and nutrient estimates with estimates obtained from food records. DESIGN: Subjects completed four 2-day food records at 3-month intervals. At the end of the recording period, a food frequency questionnaire was administered to assess usual daily intake during the preceding year. SUBJECTS/SETTING: One hundred and three subjects selected from a population-based sample of adults participating in the Beaver Dam Eye Study. STATISTICAL ANALYSES PERFORMED: Subjects were categorized into three groups on the basis of their frequency of consumption of fat-modified foods. For each group, correlations were calculated between food record estimates and estimates obtained from the original food frequency questionnaire, the original with a low-fat option, and the fat-modified questionnaire. RESULTS: For persons categorized as high consumers of fat-modified foods, incorporating questions regarding the consumption of these products resulted in higher correlations with food record estimates (original vs fat-modified version) for percentage of energy from total fat (.32 vs .47), saturated fat (.20 vs .41), oleic acid (.32 vs .50), and linoleic acid (.40 vs .46). High consumers differed in several characteristics that could be associated with disease risk (eg, higher ratios of serum total cholesterol to high-density lipoprotein cholesterol). CONCLUSIONS: Failure to account for the consumption of fat-modified foods in epidemiologic studies may result in misclassification of fat exposures. Because patterns of misclassification could be different for those at risk for disease, results of epidemiologic studies could be biased if these foods are excluded. Thus, incorporating fat-modified foods into food frequency questionnaires will improve the ability of researchers to correctly classify fat exposures and to evaluate potentially important relationships between fat intake and disease risk.

Aged↗
PubMed1997

Sleep-disordered breathing and motor vehicle accidents in a population-based sample of employed adults.

Studies have consistently shown that sleep apnea patients have high accident rates, but the generalizability of the association beyond clinic populations has been questioned. The goal of this investigation was to determine if unrecognized sleep-disordered breathing in the general population, ranging from mild to severe, is associated with motor vehicle accidents. The sample comprised 913 employed adults enrolled in an ongoing study of the natural history of sleep-disordered breathing. Sleep-disordered breathing status was determined by overnight in-laboratory polysomnography and motor vehicle accident (MVA) history was obtained from a statewide data base of all traffic violations and accidents from 1988 to 1993. Men with five or more apneas and hypopneas per hour of sleep [apnea-plus-hypopnea index (AHI) > 5], compared to those without sleep-disordered breathing, were significantly more likely to have at least one accident in 5 years (adjusted odds ratio = 3.4 for habitual snorers, 4.2 for AHI 5-15, and 3.4 for AHI > 15). Men and women combined with AHI > 15 (vs. no sleep-disordered breathing) were significantly more likely to have multiple accidents in 5 years (odds ratio = 7.3). These results, free of clinic selection bias, indicate that unrecognized sleep-disordered breathing in the general population is linked to motor vehicle accident occurrence. If the association is causal, unrecognized sleep-disordered breathing may account for a significant proportion of motor vehicle accidents.

Accidents, Traffic↗
PubMed1997

Estimation of the clinically diagnosed proportion of sleep apnea syndrome in middle-aged men and women.

The proportion of sleep apnea syndrome (SAS) in the general adult population that goes undiagnosed was estimated from a sample of 4,925 employed adults. Questionnaire data on doctor-diagnosed sleep apnea were followed up to ascertain the prevalence of diagnosed sleep apnea. In-laboratory polysomnography on a subset of 1,090 participants was used to estimate screen-detected sleep apnea. In this population, without obvious barriers to health care for sleep disorders, we estimate that 93% of women and 82% of men with moderate to severe SAS have not been clinically diagnosed. These findings provide a baseline for assessing health care resource needs for sleep apnea.

Adult↗
PubMed1997

Sleep-disordered breathing and neuropsychological deficits. A population-based study.

The relationship of sleep-disordered breathing (SOB) to neuropsychological deficits was investigated with cross-sectional data from the Wisconsin Sleep Cohort Study, a population-based study of the natural history of SDB. A sample of 841 employed men and women ages 30 to 60 yr was studied by overnight polysomnography to assess the frequency of apneas and hypopneas per hour of sleep (apnea-hypopnea index, AHI). Prior to overnight polysomnography, the participants were given a battery of neuropsychological tests for functionally important capacities including motor skills, attention, concentration, information processing, and memory. Principal factor analysis of all the neuro-psychological test data revealed a psychomotor efficiency and a memory factor. Multiple regression analysis showed a significant negative association between logarithmically transformed AHI (LogAHI) and psychomotor efficiency score independent of age, gender, and educational status (p = 0.017). The relationship was not explained by self-reported sleepiness. No significant relationship was seen between LogAHI and memory score. In assessing the clinical significance of mild SDB, we estimate that an AHI of 15 is equivalent to the decrement in psychomotor efficiency associated with 5 additional yr of age, or to 50% of the decrement associated with hypnosedative use.

Adult↗
PubMed1997

Long-term hyperglycemia is related to peripheral nerve changes at a diabetes duration of 4 years. The Wisconsin Diabetes Registry.

OBJECTIVE: To examine longitudinal hyperglycemia and peripheral nerve responses in a population-based incident cohort. RESEARCH DESIGN AND METHODS: A sample from an incident cohort of young people was comprehensively followed from diagnosis of IDDM. Participants were invited to submit blood samples three times per year for central testing of GHb. During their 4th year of diabetes, nerve conduction studies were performed on the median sensory and motor, peroneal motor, and sural sensory nerves. Relationships between mean GHb and nerve latencies, velocities, and amplitudes were explored. RESULTS: GHb was positively related to all nerve latencies and negatively related to all nerve velocities. The relationships between mean GHb and nerve conduction latencies and velocities differed by sex for the peroneal nerve latency (beta = 0.17 male subjects, beta = -0.01 female subjects; P < 0.001). Pubertal participants had lower velocities and longer latencies than prepubertal participants (beta = 0.37; P = 0.05 peroneal latency), after adjustment for GHb, height, and extremity temperature. Sensory and motor nerve amplitudes were related to GHb, and these relationships did not differ by sex. CONCLUSIONS: Our study indicates that sustained hyperglycemia is related to functional changes, at the minimum, in peripheral sensory and motor nerve conduction at a diabetes duration of 4 years. Our findings are consistent with a dying-back neuropathy, and there is some suggestion that chronic hyperglycemia may be more detrimental to nerves in male subjects than in female subjects.

Adolescent↗
PubMed1997

Effect of omitted confounders on the analysis of correlated binary data.

Marginal analysis using the generalized estimating equation approach is widely applied to correlated observations, as occur in studies with clusters and in longitudinal follow-up of individuals. In this article, we investigate the effect of confounding in such models. We assume that a risk factor x and a confounder z are related by a generalized linear model to the outcome y, which can be binary or ordinal. In order to investigate confounding arising from the omission of z, a joint structure for x and z must be specified. Modeling normally distributed (x,z) as sums of between- and within-individual (or cluster) components allows us to incorporate different degrees of between- and within-individual correlation. Such a structure includes, as special cases, cohort and period effects in longitudinal settings and random intercept models. The latter situation corresponds to allowing z to vary only on the between-individual (or cluster) level and to be uncorrelated with x, and leads to attenuation of the coefficient of x in marginal models with the logit and probit links. More complex situations occur when z is allowed to also vary on the within-individual (or cluster) level and when z is correlated with x. We examine the model specification and the expected bias when fitting a marginal model in the presence of the omitted confounder z. We derive general formulas and interpret the parameters and results in an ongoing cohort study. Testing for omitted covariates is also discussed.

Adult↗
PubMed1997

Dysbaric osteonecrosis in divers and caisson workers. An animal model.

Dysbaric osteonecrosis was induced successfully in adult sheep after 12 to 13, 24-hour exposures to compressed air (2.6-2.9 atmospheres absolute) during a 2-month period. All exposed sheep had decompression sickness and extensive bone and marrow necrosis in their long bones. Radiographic analysis of these progressive lesions showed mottled to distinct medullary opacities and endosteal thickening characteristic of dysbaric osteonecrosis. Six months after the last hyperbaric exposure, neovascularization of once ischemic fatty marrow was centripetal from the diaphyseal cortex. Proliferating endosteal new bone, fatty marrow calcification, and appositional new bone formation were widespread. Juxtaarticular osteonecrosis involved marrow fibrosis and loss of osteocytes in subchondral cortical bone. Tidemark reduplication in juxtaarticular bone and cartilage thinning suggested possible early osteoarthritis induction by recurrent episodes of transient ischemia after multiple hyperbaric exposures. Dysbaric osteonecrosis appears to involve a bone compartment syndrome of elevated intramedullary pressure initiated by decompression induced N2 bubble formation in the fatty marrow of the long bones. An animal model that can be used to investigate the pathogenesis, diagnosis, and treatment of dysbaric osteonecrosis is discussed.

Animals↗
PubMed1996

The gender bias in sleep apnea diagnosis. Are women missed because they have different symptoms?

BACKGROUND: Population-based studies have shown that sleep apnea is underdiagnosed in women, relative to men. One hypothesis for this gender bias is that women with sleep apnea are missed because clinical guidelines for the evaluation and diagnosis of sleep apnea, established primarily on men, are not valid for women. In this investigation, data from the Wisconsin Sleep Cohort Study, a community-based study of the natural history of sleep apnea, were used to determine whether women with sleep apnea have unique symptoms or complaints. METHODS: The sample comprised 551 men and 388 women, none of whom had ever been given a diagnosis of sleep apnea. Data on typical sleep apnea symptoms and other factors were obtained by interview and survey. Sleep apnea status was determined from the frequency of apneic and hypopneic events during sleep as recorded by in-laboratory, whole-night polysomnography. The sensitivity and relative predictive power of each symptom or factor for sleep apnea at different severity levels were calculated and compared by gender. RESULTS: Regardless of severity level, women with sleep apnea did not report symptoms that differed significantly from those of men with the same level of sleep apnea. For men and women, snoring was the most sensitive and strongest predictor of sleep apnea. CONCLUSIONS: Current clinical indications for sleep apnea evaluation are as appropriate for women as they are for men. Other reasons for the gender disparity in sleep apnea diagnosis, including the possibility that health care providers disregard typical symptoms in women, should be pursued.

Diagnosis, Differential↗