F. De Meyer

Components of biological variation, including seasonality, in blood concentrations of TSH, TT3, FT4, PRL, cortisol and testosterone in healthy volunteers

OBJECTIVEThere are few detailed studies of annual or seasonal variations in hormone concentrations in man. This study examines the components of biological variation, including seasonality, in plasma TSH, total T3 (TT3), free T4 (FT4), PRL, cortisol and testosterone in healthy volunteers.

Synchronized annual rhythms in violent suicide rate, ambient temperature and the light-dark span

To investigate whether violent and nonviolent suicide and homicide are related to atmospheric or geomagnetic activity, we investigated the relationships between weekly number of suicides or homicides for all Belgium for the period 1979–1987, and ambient temperature, relative humidity, air pressure, hours of sunlight and precipitation per day, wind speed and geomagnetic index. The occurrence of violent suicide was significantly and positively related to ambient temperature, sunlight duration, an increase in temperature over the few past weeks, and negatively to relative humidity. Higher ambient temperature and an increase in air temperature over the few past weeks were the most significant climatic predictors of violent suicide rate. A highly significant common annual rhythm with a common acrophase of 190° was detected in violent suicide rate, ambient temperature and sunlight duration. No significant time‐relationships between nonviolent suicide or homicide and any of the weather variables were found. It is concluded that i) violent suicide may be related to short‐term fluctuations in the weather and in particular to temperature; and ii) the annual rhythm in violent suicide may be synchronized by the annual rhythms in ambient temperature and light‐dark span.

Seasonality in severity of depression: relationships to suicide and homicide occurrence

Some previous studies have reported seasonal or monthly variations in the occurrence of depressive syndromes. The present study was carried out in order to investigate seasonality in severity of depression. Toward this end, the authors measured the Zung Self‐Rating Depression (ZD) and Anxiety (ZA) Scales scores in 104 consecutively admitted depressed patients between November 1983 and April 1985. The data were analyzed by means of spectral analysis of a single time series. Up to 47.9% of the variance in the weekly average of the ZD scores could be explained by two significant rhythms of 51 (circannual) and 7 weeks. Peaks in ZD scores were observed in April‐May, with lows occurring in August–September. Up to 30.8% of the variance in the weekly average of ZA scores was explained by a circannual rhythm. Our results show that there is a true seasonality in the severity of illness of depressed subjects. There were significant correlations between the weekly average in severity of illness and the chronograms of suicide (positively) and homicide (negatively) occurrence in Belgium.

Components of biological variation in serum soluble transferrin receptor : relationships to serum iron, transferrin and ferritin concentrations, and immune and haematological variables

We investigated the components of biological variation in serum soluble transferrin receptor (TfR) in relation to serum iron, transferrin (Tf), ferritin, soluble interleukin-2 receptor (sIL-2R), sIL-6R, and number of erythrocytes, haemoglobin (Hb), haematocrit (Ht), mean corpuscular volume (MCV), mean cell haemoglobin (MCH), and erythrocyte distribution width (RDW). We took monthly blood samples during 1 calendar year from 26 healthy subjects for assay of the above variables. The estimated CVs for TfR were interindividual CVg = 20.8%, and intra-individual CVi = 13.6%; for Tf, CVg = 14.4% and CVi = 6.7%; for iron, CVg = 16.8% and CVi = 29.2%; and for ferritin, CVg = 71.1% and CVi = 26.5%. There was a statistically significant seasonal pattern in the four variables with significant annual, biannual and/or trimonthly rhythms, which were expressed as a group phenomenon. The peak-trough differences in the yearly variations, expressed as a percentage of the mean, were: for TfR, 11.7%; for iron, 39.2%; for Tf, 11.7%; and for ferritin, 29.3%. Up to 34.2% of the within-subject variability in TfR (which reflects changes over time) could be explained by the regression on iron, ferritin, Tf, sIL-2R, sIL-6R and MCH values. Up to 67.2% of the between-subject variability in TfR (which reflects differences in the homeostatic setpoint during the study year) could be explained by the regression on gender, iron, Tf, and ferritin values.

Spectral resolution of cardio-circulatory variations in men measured by autorhythmometry over 2 years.

An analogue of the periodogram method for unequally spaced data is presented with a view to resolving the frequency structure of the observations. The algorithm is explicitly based on the sequential least squares procedure. In particular, the key concept is that the with-in-plot spectral analysis can be augmented by the between-plot information to make inferences about common characteristics. It is also shown how the between-plot random variations can be incorporated into the multiple harmonic regression model. A detailed spectral analysis investigates the periodic fluctuations in four cardio-circulatory variables, measured by autorhythmometric observation by eight men at rest and extending over a time span of 2 years. The spectral curves show the existence of circadian and circaseptan rhythmicities. The amplitude modulation of the dian rhythm by circaseptan variation is assimilated with the rhythmicity of work during the week. The blood-pressure variables situate their maximum annual peak in the winter period. These quasi-periodic fluctuations appear to be related to the amount of physical activity performed in time by the subjects.

The periodicities in and biometeorological relationships with bed occupancy of an acute psychiatric ward in Antwerp, Belgium

Recently, some investigators have established a seasonal pattern in normal human psychology, physiology and behaviour, and in the incidence of psychiatric psychopathology. In an attempt to elucidate the chronopsy and meteotropism in the latter, we have examined the chronograms of, and the biometeorological relationships to bed occupancy of the psychiatric ward of the Antwerp University Hospital during three consecutive calendar years (1987–1989). Weather data for the vicinity were provided by a local meteorological station and comprise mean atmospheric pressure, air temperature, relative humidity, wind speed and minutes of sunlight and precipitation/day. The number of psychiatric beds occupied during the study period exhibited a significant seasonal variation. Peaks in bed occupancy were observed in March and November, with lows in August. An important part of the variability in the number of beds occupied could be explained by the composite effects of weather variables of the preceding weeks. Our results suggest that short-term fluctuations in atmospheric activity may dictate some of the periodicities in psychiatric psychopathology.

Mathematical modelling of the sunspot cycle

The sunspot record for the time interval 1749–1977 can be represented conveniently by an harmonic model comprising a relatively large number of lines. Solar activity can otherwise be considered as a sequence of partly overlapping events, triggered periodically at intervals of the order of 11 years. Each individual cycle is approximated by a function of the Maxwell distribution type; the resulting impulse model consists of the superposition of the independent pulses. Application of these two models for the prediction of annual values of the Wolf sunspot numbers leads to controversial results. Mathematical modelling of the sunspot time series does not give an unambiguous result.

Modulation of the Solar Magnetic Cycle

The modulation model of the solar magnetic cycle for the time interval from 1650 to 1996 A.D. describes an harmonic oscillator with a basic (22.13 ± 0.05)-yr period, which is subjected to amplitude and phase variations that can be represented by a sum of trigonometric series. The simulated sunspot data explain 97.9% of cycle peak height variance and the residual standard deviation is 8.6 mean annual sunspots. A peak height of 139 for cycle 23 occurring in 2001 is predicted, whereas cycle 24 would have a maximum around 132 in 2014. Simulation of the sunspot numbers from 1000 until 2400 A.D. shows that the model recreates recurring minima (Maunder and Sporer Minimum). The prediction also expects a high level of amplitude modulation in the interval 1950–2010 with a rapid decrease afterwards. A greatly reduced cycle activity is reproduced by the simulation from about 2065 to 2100 A.D. No direct explanation of the long-term periodicities of the model can be advanced. The high-frequency contribution of the phase modulation, which accounts for the skewness of the solar cycle, shows coincidences with the orbital periods of Jupiter and Saturn, but no physical basis for the matching periodicities can be conceived.The modulation model of the solar magnetic cycle for the time interval from 1650 to 1996 A.D. describes an harmonic oscillator with a basic (22.13 ± 0.05)-yr period, which is subjected to amplitude and phase variations that can be represented by a sum of trigonometric series. The simulated sunspot data explain 97.9% of cycle peak height variance and the residual standard deviation is 8.6 mean annual sunspots. A peak height of 139 for cycle 23 occurring in 2001 is predicted, whereas cycle 24 would have a maximum around 132 in 2014. Simulation of the sunspot numbers from 1000 until 2400 A.D. shows that the model recreates recurring minima (Maunder and Spörer Minimum). The prediction also expects a high level of amplitude modulation in the interval 1950–2010 with a rapid decrease afterwards. A greatly reduced cycle activity is reproduced by the simulation from about 2065 to 2100 A.D. No direct explanation of the long-term periodicities of the model can be advanced. The high-frequency contribution of the phase modulation, which accounts for the skewness of the solar cycle, shows coincidences with the orbital periods of Jupiter and Saturn, but no physical basis for the matching periodicities can be conceived.

Statistical analysis of Piccardi chemical tests

The numerical data collected daily for the longest series of inorganic chemical tests, carried out in Florence (Piccardi and co-workers, 1951–1972) and in Brussels (Capel-Boute, 1956–1978), have been submitted to a statistical analysis for the purpose of searching an answer to the questions which led to start the collection of long-term series of data with the Piccardi chemical tests in different places. The question was to study the variability in the course of time of various effects observed on aqueous systems, even in the most rigorously standardized conditions, for a chemical precipitation reaction. Since significant long-term perturbations and an annual variation are present in all data sets, the observations cannot be conceived as purely random fluctuations. No common long-term pattern is observed and the measurements are not unambiguously correlated with climatological effects or the solar cycle. The statistical information content of the chemical tests is time-dependent, which implies non-stationarity of the observations. These results suggest the necessity of search for disturbing geophysical and cosmological factors to understand the mechanisms of the interaction.

Rheological modelling of physiological variables during temperature variations at rest.

The evolution with time of cardio-respiratory variables, blood pressure and body temperature has been studied on six males, resting in semi-nude conditions during short (30 min) cold stress exposure (0°C) and during passive recovery (60 min) at 20°C. Passive cold exposure does not induce a change inHR but increasesVO2,VCO2Ve and core temperatureTre, whereas peripheral temperature is significantly lowered. The kinetic evolution of the studied variables was investigated using a Kelvin-Voigt rheological model. The results suggest that the human body, and by extension the measured physiological variables of its functioning, does not react as a perfect viscoelastic system. Cold exposure induces a more rapid adaptation for heart rate, blood pressure and skin temperatures than that observed during the rewarming period (20°C), whereas respiratory adjustments show an opposite evolution. During the cooling period of the experiment the adaptative mechanisms, taking effect to preserve core homeothermy and to obtain a higher oxygen supply, increase the energy loss of the body.