Pollens et effets sanitaires : synthèse des études épidémiologiques

Allergic rhinitis grew up by threefold in French population in the last 25 years. In this context, we conduced a review on the relationships between pollens and health effects. Three fields are discussed: assessment of exposure in epidemiological studies, relationships between pollens and health effects, finally the results of the retained studies are presented. In epidemiological studies, population exposure to pollens is always done by outdoor stationary measurement. Relationships between aeroallergen concentrations and clinical effects are difficult to study because some factors as individual susceptibility, differences in the potential noxious effect of each allergen; lag between pollen and clinical effects, concentration limit that start up clinical effects and concentration limit for maximal effect; the successive productions and emissions of the different kinds of pollens; and multi-sensibility. Studying these relationship needs also to take into account several confounding factors such as: meteorological parameters, fungal aeroallergens concentrations; chemical air pollutants concentrations. Most of the epidemiological studies analyse the relationship between daily variations in pollen counts and daily variations in health effects quantified at individual levels in specific populations (panel study) or quantified at population levels (time-series). A review was already realised on studies published between 1978 and 1995 that examined the relationship between pollens and allergic rhinoconjunctivitis. Only 16 of the published studies had been retained (15 panels and one time-series). The conclusion of this work was that these studies showed associations between pollen counts and allergic rhinoconjunctivitis. But these associations could not be quantified and the dose-response curves could not be characterised because of inappropriate statistical methods and not taking into account confounding factors.In our review, nine studies that examined the short-term effect of pollen were retained for their good methodology (two of them are panels). Their results confirm associations between pollen counts and health effects and some of them succeed in quantifying the short-term effect of pollens on allergic rhinitis, allergic conjunctivitis and also asthma.     

Thromboses veineuses profondes distales isolées des membres inférieurs : épidémiologie et prise en charge

Isolated distal deep-vein thromboses (DVT) are infra-popliteal DVT without involvement of proximal veins or pulmonary embolism (PE). They can affect deep calf (tibial anterior, tibial posterior, or peroneal) or muscular (gastrocnemius or soleal) veins. They represent half of all lower limbs DVT. Proximal and distal DVTs differ in terms of risk factor profile, proximal DVT being more frequently associated with chronic risk factors and distal DVT with transient ones. Their natural history (rate of spontaneous proximal extension) is debated leading to uncertainties on the need to diagnose and treat them with anticoagulant drugs. In the long term, the risk of venous thromboembolic recurrence is lower than that of proximal DVT and their absolute risk of post-thrombotic syndrome is unknown. French national guidelines suggest treating with anticoagulants for 6 weeks a first episode of isolated distal DVT provoked by a transient risk factor and treating for at least 3 months unprovoked or recurrent or active cancer-related distal DVT. The use of compression stockings use is suggested in case of deep calf vein thrombosis. Ongoing therapeutic trials should provide important data necessary to establish an evidence-based mode of care, especially about the need to treat distal DVT at low risk of extension with anticoagulants.     

Exposition aux particules atmosphériques fines et développement des maladies allergiques de l’enfant. Résultats épidémiologiques issus de l’étude des six villes (ISAAC-2 France)

To evaluate whether fine air particles could be involved in the occurrence of atopy and allergic diseases, we performed a cross-sectional epidemiological survey involving primary schoolchildren living in six French towns with contrasted air pollution levels. Air pollution was measured during a week in the schoolyards and by standard air monitoring networks. Children get an examination in school looking for atopic dermatitis and bronchial hyperresponsiveness assessed by a standardized run test. Besides, parents or guardians provided past medical history and environmental data, especially on passive smoking. Overall, 5338 children, aged 10.4 (± 0.7) years, coming from 108 different schools and 401 different classes were included in the survey. Taking into account potential confounders, high exposure to proximity PM_2.5 was linked to a higher-point prevalence of atopic dermatitis and hyperresponsiveness, to a higher cumulative prevalence of allergic asthma and a higher sensitization rate to common indoor allergens. Thus, these data suggest that chronic exposure to urban fine particles could be a risk factor for atopy, hyperresponsiveness and asthma.