Background: Strategies to prevent primary headaches could be very beneficial, especially given that primary headaches can lead to the development of chronic headache. In order to establish headache prevention strategies, the modifiable risk factors for primary headaches need to be identified.
Material and methods: A systematic literature search on the risk factors for primary headaches was conducted independently by two persons using the databases MEDLINE and Embase. Further inclusion criteria were observational studies in adult general populations or case-control studies, where the effect sizes were reported as odds ratios or where the odds ratios could be calculated from the given data.
Results: In all, 24 studies were included in the analysis. There was a large amount of heterogeneity among the studies concerning headache acquisition, headache classification, and risk factors for headache development. Independent of headache trigger and definition of headache, the association between headache and the risk factor "stress" was very high: The meta-analysis shows an overall effect of 2.26 (odds ratio; 95 %-CI = [1.79; 2.85]). Studies evaluating neck and shoulder pain also report a strong association with headache; however, these results could not be summarized in a meta-analysis. Equally, the overall effects of smoking and coffee consumption on headaches could not be verified because the effect sizes were rather small and predominantly noticeable only at higher doses.
Conclusion: A strong association between headache and the risk factors stress and neck and shoulder pain was confirmed. The effect sizes of smoking and coffee consumption on headaches were rather small.