Daily, monthly and seasonal variation in PSA levels and the association with weather parameters.

PSA levels have shown daily and seasonal variation, although data are conflicting regarding the season with higher PSA levels and the clinical relevance of this. We assessed the correlation of total PSA levels with meteorological data on a daily, weekly, monthly and seasonal basis. Data from 53,224 men aged 45-74 years, with an initial PSA <10.0 ng ml(-1) were correlated with temperature (°C), duration of bright sunshine (hours) and rainfall (mm). There was seasonal variation in PSA levels, with median PSA being higher in spring compared with other seasons (1.18 vs 1.10 ng ml(-1), P = 0.004). Seasonal variation was not apparent when PSA levels were age-adjusted (P = 0.112). Total PSA was not correlated with daily, weekly or monthly hours of sunshine, rainfall or mean temperature. In contrast, age-adjusted PSA varied with weekday, with higher PSA levels on Thursday and Friday compared with other days (1.16 vs 1.10 ng ml(-1), respectively). On multivariate analysis, only age predicted for PSA levels >3.0 ng ml(-1). In conclusion, PSA levels did show seasonal variation, although there was no direct correlation between PSA and any meteorological parameter. The degree of seasonal variation is small and the decision to proceed to prostate biopsy should be independent of season or weather parameters.