Both high and low levels of haemoglobin may be associated with the development of dementia years later suggests a study. The study was published in the journal 'Neurology'. The prevalence of dementia is expected to increase threefold over the next decades with the largest increases predicted in the countries where the anaemia rate is the highest said M. Arfan Ikram study's author. The study involved 12305 people with an average age of 65 who did not have dementia. Participants' haemoglobin levels were measured at the start of the study. Overall 745 or 6 per cent of the participants had anaemia.