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There are indications that subjects with a reduced finger CIVD response are more prone to get local cold injuries, but more epidemiological research is needed to establish a firm relationship. Although it was observed that an early CIVD onset was associated with initially superior manual performance, recent work shows that CIVD does not seem to increase manual dexterity during work in the cold.

Veel mensen associëren een hittegolf met terrasjes en strandbezoek. Maar er kleven ook negatieve kanten aan langdurige hitte. Zo stierven tijdens de hittegolf in 2008 in Nederland 1.000 tot 1.500 personen meer dan normaal in deze periode. Prof.dr. Hein Daanen vertelt over de invloed van warmte op het menselijk lichaam.

Peripheral cold injuries are often reported in mountaineers. Not only low ambient temperatures, but also the hypobaric circumstances are known to be major environmental risk factors. When the fingers are exposed to extreme cold for several minutes, cold induced vasodilation (CIVD) occurs, that is reported to have protective properties for cold injuries. Repeated immersion in cold water may lead to improved finger blood flow. In the latter study, the subjects immersed their phalanxes in ice water four times daily for one month. In this study we investigated if two weeks of repeated immersions of the hand in cold water prior to a mountain expedition to the Ama Dablam in Nepal enhanced finger blood flow response to cold.

In een mondelinge enquête is bij 154 consumenten de bekendheid met en het begrip van de voedingswaardewijzer onderzocht. Tevens werd de attitude ten aanzien van voedingswaarde-etikettering ondezocht. Het onderzoek vond plaats in Noord-Nederland, waar de dichtheid van verpakte produkten met voedingswaardewijzer relatief het grootst is. In het onderzochte gebied brengt de voedingswaardewijzer bij de helft van de respondenten een herkenningsreactie teweeg na presentatie van deze wijzer, 37% let op de wijzer. De declaraties op de voedingswaardewijzer worden door veel respondenten onjuist geïnterpreteerd. Jongeren en hoger opgeleiden blijken de voedingswaardewijzer beter te kunnen interpreteren dan andere respondenten. Respondenten staan in het algemeen positief tegenover het etiketteren van voedingsmiddelen met voedingswaardewijzers. Van de respondenten zegt 67% in de toekomst deze wijzer te zullen gebruiken. Dit gebruik lijkt gestimuleerd te worden door een indringende confrontatie van de respondenten met de voedingswaardewijzer.

We have investigated the slope of the alveolar plateau for inert tracer gases that were washed out from mixed venous blood. Two pairs of tracer gases were used (He, SFe) and (C2H2, Freon 22). The gases of each pair share almost the same blood-gas partition coefïicient but they have different diffusive properties in the gas phase. The experiments were performed in healthy subjects at rest and at three levels of exercise (75, 150,225 W). Each experiment started with the alveolar washin of the tracer gases by adding these gases to inspired air. This washin was continued for several minutes in order to dissolve suffìcient amounts of the tracer gases in the body tissues. Subsequently, the tracer gases were washed out. In this paper, the slopes of the alveolar plateaus are defined as the relative increase of the concentration per second. Steeper slopes were found for the heavier gases (SF6 and Freon 22) in comparison with those for the lighter gases of the two pairs (He and C2H2). This finding ma¡' be ascribed to the contribution of diffusionlimited gas mixing in the lung to the slope of the alveolar plateau. For each gas, the slope for the first expiration during washout (alveolar washout) was considerably smaller than that for the later part of washout (mixed venous u'ashout), and the difference amounts to about 560/o and 760/o of the slope during mixed venous washout at rest and at the highest level of exercise, respectively. As a ñrst approximation, this difference may be considered to represent the contribution to the slope of the continued gas exchange across the alveolo-capillary membrane during expiration. ln theory. this contribution can be computed from the ratio of the alveolar ventilation and alveolar volume (VA/VA), and this is confirmed by our results.

Als de vingers van een mens in een koude omgeving komen, vernauwen vrijwel direct de bloedvaten in de huid. Hierdoor houdt het lichaam meer warmte vast. In de vingers kan deze reactie tot problemen leiden: de kou leidt tot minder beweeglijkheid en gevoel van de vingers, waardoor de handvaardigheid afneemt en de kans op koude-letsel toeneemt. Gelukkig vinden we in de vingertoppen Arterio-Veneuze Anastomozen (AVA). Dit zijn kortsluitingen tussen het slagaderlijke en aderlijke bloedvatstelsel. Deze gaan in de kou ritmisch open en dicht, en laten aldus pulserend bloed en daarmee warmte toe in de vingertoppen. Het opengaan van de bloedvaten in de kou wordt Cold Induced Vasodilation (CIVD) genoemd.

Throughout the 24-hour day, the occurrence of sleep and wakefulness is closely related to changes in body temperatures. Changes in skin temperature may causally affect the ability to initiate and maintain sleep. First, we briefly summarize a previously proposed neurobiological mechanism that couples skin temperature to sleep propensity. Next we review previous findings on the relation between skin temperature and sleep-onset latency, indicating that sleep propensity can be enhanced by warming the skin to the level that normally occurs prior to – and during – sleep. Finally, we present new data indicating age- and insomnia-related changes in the sleep-onset latency response to foot warming, and evaluate whether different methods of foot warming could provide an applicable strategy to address sleep complaints. Foot temperature manipulations included footbaths before sleep onset (1), and heatable bed socks applied either before (2) or after lights-off (3). In adults, sleep-onset was accelerated by warm and neutral bed socks after lights-off and correlated to the increase in foot temperature. This increase was attenuated in elderly subjects. In elderly subjects without sleep difficulties, sleep onset could be accelerated with neutral bed socks after lights-off and a warm footbath prior to lights-off. In elderly insomniacs, none of the treatments accelerated sleep onset. We illustrate that elderly subjects show an attenuated increase in foot temperature after lights-off and lose the relationship between pre-sleep heat-loss activation and sleep latency. The sensitivity of sleep propensity to foot warming changes with age and is attenuated in age-related insomnia. Keywords: Sleep electroencephalogram; Core body temperature; Skin temperature; Thermoregulation; Sleep-onset latency; Ageing; Insomnia; Foot warming

Study Objectives: To investigate the effect of mild manipulations of core and skin temperature on psychomotor vigilance (PVT) in young adults, elderly, and elderly insomniacs. Design: 432 PVTs were obtained during a 2-day semi-constant routine protocol, while differentially manipulating core and skin temperatures within a comfortable thermoneutral range. Setting: Sleep laboratory of the Netherlands Institute for Neuroscience. Patients or Participants: Groups of 8 sex-matched young adults (27.0±2.4 years, mean±s.e.m.), elderly (65.8±2.8 years), and insomniacs (59.1±1.9 years). Measurements and Results: During the 7-minute PVTs, response speed typically declined with increasing time-on-task. Proximal skin warming by only ±0.6'C accelerated this decline by 67% (P = 0.05) in young adults and by 50% (P<0.05) in elderly subjects. In elderly insomniacs, proximal warming slowed down the mean response speed already from the onset of the task (3% level drop, P<0.001). Response speed tended to decrease with age (P<0.10), reaching significance only in elderly insomniacs (P<0.05). Speed decrements occurred mostly towards the end of the time-on-task in young adults; earlier and more gradually in elderly without sleep complaints; and very early and in a pronounced fashion in insomniacs. Interestingly, the worsening by warming followed the time pattern already present within each group. Conclusions: The results are compatible with the hypothesis that the endogenous circadian variation of skin temperature could modulate vigilance regulating brain areas and thus contribute to the circadian rhythm in vigilance. Minute-by-minute PVT analyses revealed effects of age and insomnia not previously disclosed in studies applying time-point aggregation. Our data indicate that "age-related cognitive slowing" may result, in part, from age-related sleep problems.

Iedere sporter kent het fenomeen: in de zomer loopt de hartslagfrequentie veel sneller op dan in de winter. Als de duur en de intensiteit (snelheid, uitwendig vermogen) van de inspanning identiek zijn zal het hart onder warme omstandigheden toch sneller slaan. Hoe komt dit en wat ziin de praktische consequenties?

De twee artikelen, o.a. Sluijs, H. van der, Enkele waarnemingen d.m.v. huidplethysmografie bij aandachtsconcentratie, in dit geschrift gebundeld zijn de bwerkte teksten van inleidingen, uitgesproken tijdens de Nederlnadse Vereniging voor Arbeids- en Bedrijfsgeneeskunde, gehouden op 22 februari 1973 in het Nederlands Instituut voor Praeventeive Geneeskunde. Het was oorspronkelijk de bedoeling, deze teksten te publiceren in "Mens en Onderneming"- tijdschrift uitgaande van het NIPG/TNO - maar omdat zij niet pasten in de redaktionele doelstelling van dit blad is besloten, ze afzonderlijk te publiceren.

Dìet is considered to be a potentiaì1y modifiabìe exposure which mìght give opportunities to reduce breast cancer incidence (l ). It is, however, not known whìch specìfic factors are the most important causes of breast cancer in the Netherlands. Results of correlation studies suggest that the relatìveìy high Dutch breast cancer incidence and mortality (2) mìght be expìained by the high per capita fat intake (3) and the presumabìy low selenium intake (4). These associations are al so demonstrated in animal studies (5). Up to now, case-control sttudies on diet and breast cancer have mainly focused on animal products (6) or dietary fat (6-8) and consumption of alcoholic beverages (9-ll). Also, in two cohort studies (12,13) positive associations with animal products and fat-containing foods were found, while several Japanese foodstuffs were negatively associated. These dìetary components are thought to promote neoplastic disease. 0n the other hand, selenium is suggested to be a protective agent against cancer ìn generaì (14). Case-control studies showed contradictory results in blood selenium levels between breast cancer cases and controls (15,16). Two recent prospectìve studies have reported an inverse relation between a low prediagnostrc selenium level and subsequent (all sites) cancer risk (14,17). 1n general, however, these studies were small and site specific analyses could not be studied wìth much statistical power (14,l8). Also, a protective effect has been found of increased blood levels of vitamin t, possibly of ß-carotene, but not of serum retinol (l9).