Headache frequency is typically determined by the average number of headache days per month in the last 3 months and headache history length as the duration in years between the first migraine episode and the date of the first visit to a headache clinic. As the number of headaches you experience increases, the more headaches you are likely to incur. Headaches that occur 5 days per month, that don't even last all days, increase your risk 6 X that they may happen more than 15 days per month in the next year in comparison with individuals with fewer headaches. Ten (10) days with some degree of headache increases your risk 20 X compared to those with 0-4 HA days, sometimes even leading to everyday HA, according to the American Migraine Foundation.