Three of these nucleotides are also thought to be associated with sleep and sedation. A team of Spanish researchers collected breast milk over a twenty-four hour period from thirty healthy moms who had been breast-feeding for at least three months. They found that the concentrations of these three specific nucleotides associated with sleep and sedation were highest in milk expressed at night, and decreased during the day. In a follow-up study the researchers created a night-time formula for bottle-fed babies that contained higher concentrations of the three sleep-related nucleotides than normal infant formula. Infants who received normal formula during the day, and night-time formula after six p.m., fell asleep faster and slept longer than when they were given normal formula milk twenty-four hours a day.