**4. Late onset of dementia with mosaic trisomy of chromosome 21**

For most of the younger and many of older participants too, changes in ABS scores were minimal (Figure 1). Slight improvement in scores at ages 38-40 was seen in an participant after a change of residence, coupled with increasing exercise, weight loss and improved fitness. The highest scores with slight improvement at ages 38-43 were seen in a participant in spite of many treated health problems, including a slight permanent visual impairment, hypothyr‐ oidism, fractures associated with osteoporosis and bronchial asthma.

The ABS scores declined in most participants with Alzheimer´s disease (Figure 2). Improve‐ ments in ABS scores were seen in two elderly participants. In the first participant (Figure 2), the improvement at age 42 to 43 associated to the change of residence and medical treatment of Alzheimer's disease with response for two years before advancing deterioration later. Epilepsy and loss of mobility after a fall resulting in a hip fracture, and poor visual acuity contributed to the loss of independent functioning.

The improvement of the other participant (Figure 3) during the treatment of confirmed Alzheimer's disease, after a decline at age 48 to 49 lasted five years before further deterioration. Contributing factors to the functional improvement were the removal of cataracts resulting in improved visual acuity, active participation in activities with support of the carers, and stabilization of mood and behaviour. This participant had a long history of hypothyroidism, depression and challenging behaviour and he had long-term antidepressant and antipsychotic medication, and successful treatment of late onset epilepsy.
