They did comment on the issue in their discussion: "We examined whether age was an important factor in producing the baseline differences we observed by comparing the three youngest practitioners with the controls and found that the mean age difference between groups is unlikely the sole factor responsible for this baseline difference. Moreover, hours of practice but not age significantly predicted relative gamma activity during the initial baseline period."
They did comment on the issue in their discussion: "We examined whether age was an important factor in producing the baseline differences we observed by comparing the three youngest practitioners with the controls and found that the mean age difference between groups is unlikely the sole factor responsible for this baseline difference. Moreover, hours of practice but not age significantly predicted relative gamma activity during the initial baseline period."