Thromb Haemost 2011; 106(03): 439-447
DOI: 10.1160/TH11-02-0116
Blood Coagulation, Fibrinolysis and Cellular Haemostasis
Schattauer GmbH

Seasonal and monthly variability in the incidence of venous thromboembolism

A systematic review and a meta-analysis of the literature
Francesco Dentali
1   Department of Clinical Medicine, University of Insubria, Varese, Italy
,
Walter Ageno
1   Department of Clinical Medicine, University of Insubria, Varese, Italy
,
Elena Rancan
1   Department of Clinical Medicine, University of Insubria, Varese, Italy
,
Alberto V. Donati
1   Department of Clinical Medicine, University of Insubria, Varese, Italy
,
Luca Galli
1   Department of Clinical Medicine, University of Insubria, Varese, Italy
,
Alessandro Squizzato
1   Department of Clinical Medicine, University of Insubria, Varese, Italy
,
Achille Venco
1   Department of Clinical Medicine, University of Insubria, Varese, Italy
,
Pier Mannuccio Mannucci
2   Department of Medicine and Medical Specialties, IRCCS Cà Granda Foundation Maggiore Policlinico Hospital, Milan Italy
,
Roberto Manfredini
3   Department of Clinical and Experimental Medicine, Clinica Medica and Vascular Diseases Center, University of Ferrara, Italy
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Publikationsverlauf

Received: 20. Februar 2011

Accepted after major revision: 02. Juni 2011

Publikationsdatum:
01. Dezember 2017 (online)

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Summary

Many studies showed that the occurrence of cardiovascular and cerebrovascular events exhibits a seasonal and monthly variation. Evidences of a seasonal and monthly variation in the incidence of venous thromboembolism (VTE) are more conflicting. We conducted a systematic review and a meta-analysis of the literature to assess the presence of an infradian rhythm of this disease. MEDLINE and EMBASE databases were searched up to January 2010. Monthly and seasonal variation in the incidence of VTE were analysed. We included studies analysing seasonal or monthly aggregation in the incidence of deep-vein thrombosis (DVT) and/or pulmonary embolism (PE) with an objective diagnosis of VTE. Two authors independently reviewed and extracted data. Seventeen studies for a total of about 35,000 patients were included. Twelve studies analysed the seasonal variation and 10 studies the monthly variation of VTE. Our results showed a significantly increased incidence of VTE in winter (chi-square 146.04, p <0.001), with a relative risk (RR) of VTE of 1.143 (99% CI [1.141, 1.144]), and a significantly increased incidence of VTE in January (chi-square 232.57, p <0.001) with an RR of VTE of 1.194 (99% CI 1.186, 1.203). Subgroup analyses including only idiopathic venous thromboembolic events confirmed the results of principal analyses. In conclusion, our data support the presence of an infradian pattern in the incidence of venous thromboembolic events, with a significantly higher risk in Winter and in January. Future studies are needed to better clarify the mechanisms behind this pattern.