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Biomedical subjects

F Halberg

Publications and source records attributed to F Halberg.

At least 127 records · Page 7Linked to original sources
PubMed1990

Nonparametric testing of melatonin characteristics as potential markers of breast cancer risk.

On the average, the circadian A of ML is larger in clinically healthy women at high vs. low RDBC. The original finding was made without numerical sampling on data from a relatively small group of women sampled systematically around the clock and the year. It was hence of further interest to see whether the risk-related difference can be corroborated by numerical resampling, i.e., by BS, a fairly general, usually computerintensive technique used for estimating the sampling distribution of an estimator or statistic (i.e., a quantity computed from the data). For BS of circannual parameters, one here assumes that 1) circadian As (obtained by the fit of a 24-hour cosine curve by linear least squares) are correlated for any given subject from season to season; and 2) deviations of each circadian A from the average are random. The method then estimates the characteristics of harmonic components, ordered by P-values obtained by linear least-squares analysis involving a test of the assumption of zero A for each special component. Results from BS validate differences in circadian A of ML between the low and high RDBC groups throughout the year. The use of BS serves to introduce inferential considerations into discriminant analysis and to test results obtained with very limited samples sizes, before embarking upon the actual labor-intensive, costly resampling required in circannual and circadian work. BS is a procedure recommended for broad routine use in non-parametric hypothesis testing and biomedical signal simulation. The re-evaluation of ML data by BS provides further inferential statistical validation of the finding as a first complement, not substitute, for additional sampling in order to assess a possibly important component of a test battery for breast cancer risk.

Biomarkers↗
PubMed1990

Ambulatory cardiovascular monitoring of healthy adults in Rochester, Minnesota: chronobiologic assessment.

To serve as a tentative reference group for clinical health, 107 adults measured their systolic (S) and diastolic (D) blood pressure (BP) with an ambulatory Del Mar Avionics monitor (Irvine, California). Data were collected over approximately 24 hours at 7.5-minute intervals during waking and at 15-minute intervals during sleep. An echocardiogram served to determine the left ventricular mass (LVM), septal wall thickness (SWT), posterior wall thickness (PWT), ejection fraction (EjFr), and left atrial size (LAS). Each data series was analyzed by single cosinor. A statistically significant circadian rhythm (P less than 0.05) was found in 96 subjects (89.7 percent) for SBP and in 86 subjects (80.4 percent) for DBP. A population-mean cosinor reveals a highly significant circadian rhythm (P less than 0.001) for both variables in men (n = 44) as well as in women (n = 63), with an acrophase around 14:15. The double circadian amplitude, a measure of the total predictable change within a day, averages 10 (women) and 11 (men) mm Hg for DBP and 14 (women) and 17 (men) mm Hg for SBP. The midline-estimating statistic of rhythm (MESOR) of SBP is found to be higher for men (125 mm Hg) than for women (120 mm Hg), P = 0.018, whereas no difference in MESOR is found for DBP (71 mm Hg). A statistically significant correlation with age is found for the MESOR of SBP in both men (r = 0.352; P = 0.018) and women (r = 0.336; P = 0.007). The MESOR of SBP is also found to correlate with LVM in men (r = 0.300; P = 0.046), but not in women (r = 0.181; P = 0.153), whereas the MESOR of DBP correlates with LVM in women (R = 0.316; P = 0.011) but not in men (r = 0.117; P = 0.543). A positive correlation is also found between the MESOR of SBP and SWT as well as with EjFr, which is more prominent in women; between the MESOR of DBP and LAS, which is more prominent in men; and a negative correlation is found for women but not men between the circadian amplitude of both SBP and DBP and EjFr. Blood pressure excess (in mm Hg x h; hyperbaric index, briefly HBI; Halberg et al., 1984) was computed by comparing each profile to the upper 95 percent time-varying prediction limit of healthy peers.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1990

Further extensions of the cosinor approach to problems of the pharmaceutical industry.

The resolution of a more complex time structure than that described by the useful first approximation of a single cosinor is suggested herein. The cosinor serves the purpose of parsimony in the case of sparse and short time series, yet it can be usefully extended by assessing the variations in rhythm characteristics for treatment timing in the clinic rather than only for research.

Animals↗
PubMed1990

Endpoints of chronobiologic cardiovascular monitoring during pregnancy for planning exercise and assessing effects.

The chronobiologic question is raised whether exercise may be indicated for the pregnant woman as a general prophylactic measure and, if so, whether it should be timed according to rhythms and stage of pregnancy. This question, recently considered by others without chronobiologic focus, is here reviewed against the background of results from ongoing chronobiologic studies of blood pressure (BP) and heart rate (HR) in pregnancy. During pregnancy, the MESORs and circadian amplitudes of systolic (S), mean arterial (MA) and diastolic (D) BP are correlated with a questionnaire-assessed cardiovascular risk score. Such results were found under noisy ordinary conditions of life without accounting for effects of activity. They are group results, and as such require further work before they can contribute to identifying individuals at high risk in particular need of intervention, such as exercise. The dependence of exercise effects upon circadian rhythms should also prompt the use of rhythmometry at all ages for timing exercise, for gauging its effects and eventually for the optimization of fitness training for the population as well as for peak performance.

Blood Pressure↗