Biomedical subjects

M Palta

Publications and source records attributed to M Palta.

At least 55 records · Page 3Linked to original sources

PubMed1996

Longitudinal patterns of glycemic control and diabetes care from diagnosis in a population-based cohort with type 1 diabetes. The Wisconsin Diabetes Registry.

Glycosylated hemoglobin is an indicator of long-term glycemic control and a strong predictor of diabetic complications. This paper provides a comprehensive description of glycemic control (total glycosylated hemoglobin (GHb)) up to 4.5 years duration of diabetes by age, duration, and sex in a population-based cohort (n = 507) aged less than 20 years followed from diagnosis of Type 1 diabetes in Wisconsin during 1987-1994 Important aspects of demographics and diabetes care are described to allow comparison with other populations. Since large variations between laboratories are known to exist in the measurement of GHb, levels are also interpreted relative to the frequency of short-term complications. GHb increased after diagnosis, but leveled off after 2-3 years. Peak GHb values occurred in the age group 12-15 years. The within-individual standard deviation in GHb between tests, adjusted for age and duration was 1.6%. The mean GHb at last testing was 11.3%, with a standard deviation across individuals of 2.9%. The majority (74%) of individuals saw a diabetes specialist at least once. The mean number of insulin injections per day increased from 2.2 to 2.5 across the 4.5-year duration, and the insulin dose increased from 0.6 to 0.9 units per day per kg body weight. Despite the quite satisfactory level of care, 38% of subjects had GHb levels associated with significant short-term complications.

Adolescent↗

PubMed1996

Association of zinc and antioxidant nutrients with age-related maculopathy.

OBJECTIVE: To quantify relationships between dietary intake of zinc and antioxidant nutrients and early and late age-related maculopathy (ARM). DESIGN: A retrospective longitudinal cohort design using data pertaining to diets in the past (1978-1980), which were assessed retrospectively using a food frequency questionnaire. SETTING: Beaver Dam, Wis. PATIENTS: A 50% random sample of free-living Beaver Dam Eye Study participants, 43 to 86 years of age (N = 1968). MAIN OUTCOME MEASURE: The presence of early and late ARM determined from fundus photography. RESULTS: People in the highest vs lowest quintiles for intake of zinc from foods had lower risk for early ARM (odds ratio = 0.6, 95% confidence interval, 0.4-1.0, P for trend < .05). This relationship appeared to be stronger for some types of early ARM (increased retinal pigment) than for others. Zinc intake was unrelated to late ARM. However, small numbers (n = 30) of people with this condition limit the ability to draw conclusions about this later stage. Levels of carotenoids were unrelated to early or late ARM. Odds for early ARM were lower in people in the highest vs lowest quintiles for the intake of vitamins C or E. However, these associations were not statistically significant. CONCLUSIONS: The data are weakly supportive of a protective effect of zinc on the development of some forms of early ARM. Prospective studies are needed to further evaluate the potential influence of these and other nutritional factors on different types and stages of age-related macular degeneration.

Adult↗

PubMed1996

The relation of maternal complications to outcomes in very low birthweight infants in an era of changing neonatal care.

We examine the relation of key neonatal outcomes to pregnancy complications and to the use of antenatal steroids and investigate whether there is evidence of recent change in this relation. Complete information on pregnancy and neonatal course was available for 749 out of 949 singleton births without major congenital anomalies below 1501 g admitted to seven regional neonatal intensive care units between August 1, 1988 and June 30, 1991. Mortality was highest in infants born after labor with spontaneous rupture of fetal membranes of less than 24 hours duration (odds ratio [OR] = 1.6, 95% confidence interval [1.0, 2.6]). Spontaneous rupture of membranes of over 24 hours duration was associated with decreased risk of respiratory distress syndrome (OR = 0.42, [0.28, 0.64]) and decreased risk of patent ductus arteriosus (OR = 43, [0.28, 0.66]). Pregnancy induced hypertension was associated with increased risk of respiratory distress syndrome in those born at less than 20 weeks' gestation (OR = 6.0, [2.0, 17]). Labor with or without rupture of membranes of short duration was associated with increased risk of intraventricular hemorrhage (OR = 1.9, [1.2, 2.5]). These associations were not different in early versus late time periods of the study. Antenatal steroids were associated with dramatically reduced risk of mortality (OR = 0.20, [0.09, 0.50] ), respiratory distress syndrome (OR = 0.52, [0.32, 0.85]), and intraventricular hemorrhage (OR = 0.37, [0.21-0.65]).

Adrenal Cortex Hormones↗

PubMed1996

Snoring as part of a dose-response relationship between sleep-disordered breathing and blood pressure.

This report addresses the hypothesis that snoring without significant apneas and hypopneas (simple snoring) is associated with elevated blood pressure and cardiovascular disease (CVD). Data on blood pressure, previously diagnosed cardiovascular disease, and sleep-disordered breathing (SDB) status from a population-based sample of 580 adults was analyzed. Systolic and diastolic blood pressures, adjusted for age, sex, and body mass index, increased stepwise across categories of no SDB, simple snoring, mild, moderate, and more severe SDB (p < 0.05). A similar and significant trend was seen for CVD prevalence. The results provide evidence that simple snoring represents the beginning of the SDB severity spectrum and that simple snoring has a proportionately smaller but, nevertheless, significant, risk for elevated blood pressure and CVD.

Adult↗

PubMed1996

Fluctuations in serum magnesium levels during total intravenous anaesthesia with propofol.

Forty patients who underwent eye surgery under total intravenous anaesthesia with propofol where investigated in order to determine the fluctuations of serum magnesium levels during anaesthesia. Six blood samples were taken before anaesthesia, after induction, 1 hour later, 2 hours later, after recovery, and 24 hours after surgery. In the same time intervals, systolic and diastolic blood pressure, heart rate and temperature were recorded. The results showed a statistically significant decrease in serum magnesium levels during anaesthesia. No correlations between this decrease and the fluctuations of blood pressure, heart rate or temperature were found. These results indicate that there is a shift of magnesium into the tissue stores due to the state of anaesthesia, possibly by a direct effect of the anaesthetic agents on the cell membrane itself. Further investigation is needed with other techniques and agents employed in general anaesthesia.

Adult↗

PubMed1996

Using projection for testing goodness-of-fit in regression models for repeated measures.

Repeated measures data often occur in practice. This has led to considerable progress in the development of methods for inference in models for such data. In this paper, projection methods are proposed for examining goodness-of-fit in regression models for repeated measures. Rao's (1959, Biometrika 46, 49-58) F-test for testing a postulated mean structure using an independently identically normally distributed random sample is extended to a broad class of models including both fixed and random effects. The paper also shows how projection methods may be utilized for checking multivariate normality. In addition, application of projection to test the adequacy of extremely unbalanced models is considered. Two examples are given to demonstrate the underlying techniques.

Animals↗

PubMed1995

Diet and nuclear lens opacities.

Relations between diet and nuclear opacities in the lens of the eye were investigated in a population-based cohort of middle-aged and older adults who lived in Beaver Dam, Wisconsin. Nuclear sclerosis was assessed from photographs of the lens taken during 1988-1990 in 1,919 persons in the Beaver Dam Eye Study. Diets in the past (1978-1980) were assessed retrospectively with the use of a food frequency questionnaire in home interviews. Relations with intake of foods and nutrients were evaluated using logistic regression analyses. In men, after controlling for age, smoking, and heavy drinking, intakes of numerous nutrients in the highest versus lowest quintile were associated with 40-50 percent reduced odds of more severe nuclear sclerosis. Relations with some nutrients (vitamins A, C, and E, riboflavin, thiamin, niacin) were at least partly explained by previously identified inverse associations with multivitamin use. Relations with other nutrients (folate, alpha-carotene, and dietary fiber) appeared to reflect associations with intake of foods, particularly vegetables. Inverse associations with individual nutrients and foods were often weaker or nonexistent in women. These data indicate that the intake of vitamin supplements (in men and women) and certain foods (particularly in men) may explain associations of several nutrients with risk for nuclear sclerosis.

Adult↗

PubMed1995

A cohort study of the relationship of diabetic retinopathy to blood pressure.

OBJECTIVE: To determine whether blood pressure at baseline was associated with incidence or progression of diabetic retinopathy during a 10-year interval in a population-based cohort. PARTICIPANTS: A probability sample of all persons receiving primary care for diabetes in an 11-county area of southern Wisconsin were invited to participate in the study examinations in 1980 to 1982, 1984 to 1986, and 1990 to 1992. PROCEDURES: Blood pressure measurements, height, weight, ocular photographs, and glycosylated hemoglobin measurements were obtained and ocular examinations and a medical history interview were performed at each evaluation. MAIN OUTCOME MEASURES: Fundus photographs of seven standard photographic fields were obtained and graded according to the modified Airlie House Classification scheme. End points were incidence, any progression, or progression to proliferative diabetic retinopathy. RESULTS: At the baseline examination, 996 subjects were determined to have younger-onset diabetes and 1370 subjects had older-onset diabetes compared with 891 and 987, respectively, at the 4-year follow-up examination and 765 and 533, respectively, at the 10-year follow-up examination. In discrete linear logistic analyses, a 10-mm Hg increase in systolic blood pressure was significantly associated with incidence of retinopathy in subjects with younger-onset diabetes 10 years after the baseline examination (odds ratio, 1.27; 95% confidence interval, 1.03 to 1.57). No consistent association of blood pressure and retinopathy in subjects with older-onset diabetes was observed. Mortality did not affect the relationship of blood pressure and retinopathy. CONCLUSION: Increased systolic blood pressure at baseline was associated with a modest subsequent increased risk of incidence of diabetic retinopathy in subjects with younger-onset diabetes.

Adult↗

PubMed1995

Dietary fat and age-related maculopathy.

OBJECTIVE: To describe the relationship between type and level of fat in the diet and the prevalence of age-related maculopathy. DESIGN: Retrospective population-based study. SETTING AND PARTICIPANTS: Residents of Beaver Dam, Wis, between the ages of 45 and 84 years, participating in the Beaver Dam Eye Study and Nutritional Factors in Eye Disease Study. DATA COLLECTION: Presence and severity of age-related maculopathy were determined from masked grading of fundus photographs taken from 1988 through 1990. Diets in the past (1978 through 1980) were assessed retrospectively using a food frequency questionnaire during in-person home interviews. RESULTS: Persons with intake of saturated fat and cholesterol in the highest compared with the lowest quintile had 80% and 60% increased odds for early age-related maculopathy, respectively, after adjusting for age and intake of beer. These relationships were not influenced by adjusting for several other potential confounding variables (carotenoid intake, intake of vitamins C or E in supplements, smoking, body mass index, time spent outdoors in the summer, gender, and history of diabetes, hypertension, or cardiovascular disease). Odds ratios for late age-related maculopathy were in similar directions but were not statistically significant. CONCLUSIONS: High intake of saturated fat and cholesterol is associated with increased risk for early age-related maculopathy in the Beaver Dam population. This supports the hypothesis that atherosclerosis or its risk factors are related to age-related maculopathy. Confirmation of this finding in other populations and in prospective studies is needed.

Aged↗

PubMed1995

Serum antioxidants and age-related macular degeneration in a population-based case-control study.

OBJECTIVE: To investigate relationships between levels of tocopherols and carotenoids in the serum and age-related macular degeneration (ARMD). DESIGN: A nested case-control study within a population-based cohort. PARTICIPANTS: Cases included a sample of subjects with retinal pigment abnormalities with the presence of soft drusen (n = 127) or with late ARMD (geographic atrophy [n = 9]) or neovascular and exudative macular degeneration (n = 31). An equal number of controls (167 pairs) were selected from among participants in the Beaver Dam Eye Study. The controls had no photographic evidence of soft drusen, retinal pigment abnormalities, or late ARMD and were matched with cases for age, sex, and current smoking status. DATA COLLECTION: Presence and severity of ARMD were determined from masked grading of fundus photographs obtained from 1988 to 1990. Levels of individual carotenoids and tocopherols were determined in serum collected at the same time. RESULTS: Average levels of individual carotenoids were similar in cases and controls. Average levels of vitamin E (alpha-tocopherol) were lower in people with exudative macular degeneration (P = .03). However, the difference was no longer statistically significant after controlling for levels of cholesterol in the serum. Persons with levels of lycopene, the most abundant carotenoid in the serum, in the lowest quintile were twice as likely to have ARMD. Levels of the carotenoids that compose macular pigment (lutein with zeaxanthin) in the serum were unrelated to ARMD. CONCLUSIONS: Very low levels of one (lycopene) but not other dietary carotenoids or tocopherols were related to ARMD. Lower levels of vitamin E in subjects with exudative macular degeneration compared with controls may be explained by lower levels of serum lipids.

Adult↗

PubMed1995

Combined hypoxia and hypercapnia evokes long-lasting sympathetic activation in humans.

We studied ventilatory and neurocirculatory responses to combined hypoxia (arterial O2 saturation 80%) and hypercapnia (end-tidal CO2 + 5 Torr) in awake humans. This asphyxic stimulus produced a substantial increase in minute ventilation (6.9 +/- 0.4 to 20.0 +/- 1.5 l/min) that promptly subsided on return to room air breathing. During asphyxia, muscle sympathetic nerve activity (intraneural microelectrodes) increased to 220 +/- 28% of the room air baseline. Approximately two-thirds of this sympathetic activation persisted after return to room air breathing for the duration of our measurements (20 min in 8 subjects, 1 h in 2 subjects). In contrast, neither ventilation nor sympathetic outflow changed during time control experiments. A 20-min exposure to hyperoxic hypercapnia also caused a sustained increase in sympathetic activity, but, unlike the aftereffect of asphyxia, this effect was short lived and coincident with continued hyperpnea. In summary, relatively brief periods of asphyxic stimulation cause substantial increases in sympathetic vasomotor outflow that outlast the chemical stimuli. These findings provide a potential explanation for the chronically elevated sympathetic nervous system activity that accompanies sleep apnea syndrome.

Adult↗

PubMed1995

Insulin-like growth factor-I is related to glycemic control in children and adolescents with newly diagnosed insulin-dependent diabetes.

To address the relationship of insulin-like growth factor-I (IGF-I) to diabetes control, we determined IGF-I levels in 137 subjects age 17 yr and younger with recently diagnosed insulin-dependent diabetes mellitus in a population-based cohort study between 3 and 11 months after diagnosis (mean 4.9 months). Initial determinations of IGF-I, 24-h urine C-peptide and microalbuminuria, age, sex, height, weight, body mass index, pubertal stage, and glycosylated hemoglobin (GHb) were obtained. IGF-I levels ranged from 11-439 ng/mL, were strongly related to age (r = 0.74, P < 0.001), and were higher in females than males at any given age (P < 0.01). IGF-I was inversely related to GHb (partial r = -0.43, P < 0.001) after adjustment for sex and age. The relationship between IGF-I and GHb did not change between age groups (< 6, 6-9, > or = 10 yr of age; P = 0.50), and it did not change between prepubertal and pubertal subjects (P = 0.95). IGF-I was not related to 24-h urine C-peptide or microalbuminuria. These results suggest that lower IGF-I levels are related to poorer metabolic control of diabetes in the period following insulin-dependent diabetes mellitus diagnosis in all young persons regardless of age or pubertal status.

Adolescent↗

PubMed1995

Serum carotenoids and tocopherols and severity of nuclear and cortical opacities.

PURPOSE: To determine whether higher levels of individual carotenoids and tocopherols in the serum are related to less severe nuclear and cortical opacities within the general population. METHODS: Levels of individual carotenoids and tocopherols in the serum were determined in 400 randomly selected persons aged 50 to 84 years participating in the Nutritional Factors in Eye Disease Study of Beaver Dam, Wisconsin. Severity of nuclear and cortical opacities was assessed from lens slit lamp and retroillumination photographs taken at the same time. Relationships between serum levels of nutrients and prevalence of these opacities were evaluated using logistic regression analysis accounting for known possible confounders. RESULTS: Higher levels of individual or total carotenoids or alpha-tocopherol in the serum were not associated with less severe nuclear or cortical opacities overall. However, associations differed between men and women and within specific population subgroups. A significant trend for lower odds for either type of opacity with increasing levels of beta-carotene in the serum was observed in men. For nuclear sclerosis, this protective association with beta-carotene was found in younger but not older men. Higher levels of three other carotenoids (alpha-carotene, beta-cryptoxanthin, and lutein) in serum were significantly related to lower odds for nuclear sclerosis only in men who smoked. In contrast to these inverse associations observed in some subgroups, higher levels of some carotenoids and alpha-tocopherol often were directly associated with nuclear sclerosis, particularly in women. CONCLUSIONS: Higher levels of carotenoids and tocopherols are not consistently associated with less severe opacities in the general population.

Aged↗

PubMed1994

Testing for omitted variables and non-linearity in regression models for longitudinal data.

When fitting regression models to investigate the relationship between an outcome variable and independent variables of primary interest, there is often concern whether omitted variables or assuming a different functional relationship could have changed the conclusion or interpretation of the results. In longitudinal studies of aging, the concern with omitted variables is well known in the context of cohort and period effects, which refer to unmeasured variables systematically related to the individual's year of birth and secular trends in outcome, respectively. We present and compare three approaches to detecting omitted confounders and non-linearity in the random effects model for longitudinal data (Laird and Ware, 1982) with random slope and intercept across individuals. The first approach compares simple unweighted within and between regression coefficients, the second is the Hausman specification test for regression models, and the third approach involves testing directly the significance of functions of individual specific covariate means means i, in the random effects regression model. This last approach is motivated by the models that arise when cohort or period effects are ignored. We compare the three approaches, and illustrate their application.

Analysis of Variance↗

PubMed1994

Smoking as a risk factor for sleep-disordered breathing.

BACKGROUND: Recent evidence indicates that the prevalence of sleep-disordered breathing is remarkably high (24% for men and 9% for women) and that the public health burden attributable to sleep-disordered breathing is substantial. This investigation examines current and former cigarette smoking as potential risk factors for sleep-disordered breathing. METHODS: Data were from 811 adults enrolled in the University of Wisconsin Sleep Cohort Study, Madison. The Sleep Cohort Study is a longitudinal, epidemiologic study that uses nocturnal polysomnography to investigate sleep-disordered breathing and other disorders of sleep. The presence and severity of sleep-disordered breathing was quantified by the frequency of apneas and hypopneas per hour of sleep. RESULTS: Logistic regression analyses were used to control for potential confounding factors. Compared with never smokers, current smokers had a significantly greater risk of snoring (odds ratio, 2.29) and of moderate or worse sleep-disordered breathing (odds ratio, 4.44). Heavy smokers (> or = 40 cigarettes per day) had the greatest risk of mild sleep-disordered breathing (odds ratio, 6.74) and of moderate or worse sleep-disordered breathing (odds ratio, 40.47). Former smoking was unrelated to snoring and sleep-disordered breathing after adjustment for confounders. CONCLUSIONS: Current cigarette smokers are at greater risk for sleep-disordered breathing than are never smokers. Heavy smokers have the greatest risk while former smokers are not at increased risk for sleep-disordered breathing. Thus, smoking cessation should be considered in the treatment and prevention of sleep-disordered breathing.

Adult↗

PubMed1994

Sleep apnea and hypertension. A population-based study.

OBJECTIVE: To measure the independent association of sleep-disordered breathing (sleep apnea and habitual snoring) and hypertension in a healthy adult population. DESIGN: A cross-sectional study of blood pressure during wakefulness and sleep among participants with and without sleep-disordered breathing. SETTING: Community-based study. PARTICIPANTS: 147 men and women, aged 30 to 60 years, selected from Wisconsin State employees enrolled in the Wisconsin Sleep Cohort Study, an ongoing, prospective, epidemiologic study of sleep-disordered breathing. MEASUREMENTS: Sleep and medical history interview, nocturnal polysomnography, and 24-hour ambulatory blood pressure monitoring in all participants. RESULTS: Mean blood pressures were significantly higher among participants with sleep apnea (> or = 5 apneas or hypopneas per hour of sleep) compared with those without (131/80 +/- 1.7/1.1 mm Hg compared with 122/75 +/- 1.9/1.2 mm Hg during wakefulness and 113/66 +/- 1.8/1.1 mm Hg compared with 104/62 +/- 2/1.3 mm Hg during sleep, respectively; P < 0.05). The variability of the blood pressure during sleep was significantly greater in participants with sleep apnea or a history of snoring compared with those without (P < 0.05). After controlling for obesity, age, and sex, sleep apnea was significantly associated with hypertension in a dose-response fashion, with odds ratios ranging from 2.0 for 5 apneic or hypopneic episodes per hour of sleep to 5.0 for 25 apneic or hypopneic episodes. CONCLUSIONS: Our data indicate an association between hypertension and sleep apnea independent of obesity, age, and sex in a nonselected, community-based adult population.

Adult↗

PubMed1994

A population study. Mortality and morbidity after availability of surfactant therapy. Newborn Lung Project.

OBJECTIVE: To assess the impact of recent changes in neonatal intensive care on the mortality and morbidity of very-low-birth-weight neonates (< 1501 g). DESIGN: Prospective cohort study. SETTING: Six neonatal intensive care units in Wisconsin and Iowa. PARTICIPANTS: All very-low-birth-weight neonates who were admitted to the neonatal intensive care units the year before the availability of exogenous surfactant (n = 333), during the investigational new drug protocol for synthetic surfactant (Exosurf) (n = 347), and after the release of synthetic surfactant (n = 356) (designated as periods 1, 2, and 3, respectively). INTERVENTIONS: None. MAIN RESULTS: The percentage of neonates receiving exogenous surfactant in the three periods was 3%, 37%, and 56%, and the percentage receiving antenatal steroids was 12%, 17%, and 27% (P = .0001 for increase in both modalities). The percentage of neonates dying in the three periods was 23%, 14%, and 19% (P = .05 for downward trend). The percentage of neonates with intraventricular hemorrhage decreased in the subgroup weighing between 700 and 1350 g (35%, 28%, and 24%) (P = .04) and increased in the subgroup weighing below 700 g (8%, 41%, and 45%) (P = .03). The percentage of neonates with bronchopulmonary dysplasia increased from 21% to 36% between periods 1 and 2 (P = .003) and decreased to 27% (P = .04) in period 3. Antenatal steroid use was strongly associated with the decrease in intraventricular hemorrhage (odds ratio, 0.35) and mortality risk (odds ratio, 0.20). CONCLUSIONS: Several developments in care have contributed to changes in mortality risk, incidence of intraventricular hemorrhage, and the severity of respiratory disease in very-low-birth-weight infants.

Hospital Mortality↗

PubMed1994

A new radiographic scoring system for bronchopulmonary dysplasia. Newborn Lung Project.

OBJECTIVES: To develop a simple, clinically meaningful radiographic score for bronchopulmonary dysplasia (BPD). To investigate its reliability, validity, and usefulness and to compare it to the Edwards score. WORKING HYPOTHESIS: Our radiographic scoring of BPD is reliable, correlates with respiratory support, and provides a necessary standardization in comparing severity of respiratory disease between hospitals. STUDY DESIGN: Prospective cohort study. PATIENT SELECTION: The study included all neonates (n = 366) with birth weight below 1501 g admitted to 7 neonatal intensive care units, who had chest radiographs taken at age 25-35 days. METHODOLOGY: A simple radiographic scoring system was developed. Scores ranging from 0 to 6 were assigned based on standard radiographs and descriptors of degree of abnormality. All radiographs taken between days 25 and 35 of age (n = 1087) were graded by a radiologist and a neonatologist. Radiographs from a stratified random sample of 37 neonates (10%) were also scored by the method of Edwards (n = 128 radiographs). A respiratory support index was constructed for days 25-35 and correlated with the radiographic score. RESULTS: Between-reader correlation was r = 0.87 for our score and r = 0.88 for the Edwards score. The two scores correlated with each other at r = 0.94. The respiratory support index correlated with our radiographic score at r = 0.75 overall, and r = 0.56 to 0.88 within hospitals. Higher postnatal corticosteroid use was found at the hospitals with the lower correlations. CONCLUSIONS: Our radiographic scoring is reliable, valid, and gives results similar to the Edwards score. Radiographs play a standardizing role in assessing severity of BPD between hospitals.

Age Factors↗