Seasonal variation in vascular function: a systematic review and recommendations for future research.

Vascular function serves as a prognostic marker for cardiovascular disease and may exhibit seasonal variations due to lifestyle and environmental factors. Our systematic review aimed to determine whether seasonal variations in vascular function are present. We conducted a search of five databases (MEDLINE via PubMed, CINAHL, Web of Science, Cochrane Library, and Biomed Central) to identify evidence of seasonal variations in vascular function. Studies were eligible for inclusion if they assessed vascular function in adult humans during two or more seasons and were published in English. Of the 20,420 studies screened, 12 were eligible and none were excluded due to bias. Nine studies reported significant seasonal variations in vascular function, whereas three studies found no significant seasonal variations. The seasonality of vascular function remains unclear. However, current literature indicates that vascular dysfunction may exhibit a seasonal pattern, with vascular function reduced in the winter. Seasonal variations in endothelial function necessitate further exploration, particularly concerning factors such as exercise, temperature, light exposure, and air pollution. Future research should adopt standardised protocols, involve diverse and larger populations, employ longitudinal designs to minimise confounding factors, systematically measure and adjust for environmental variables, and accurately assess the impact of seasonal variation on vascular function.