- Genetic risk of Alzheimer’s disease becomes “less risky” over time.
Having a parent or sibling with Alzheimer’s disease becomes less predictive of developing dementia with age and with the age of Alzheimer’s onset in the affected relative, according to a new study reported in the Archives of General Psychiatry. Researchers have known that having a relative who was diagnosed with Alzheimer’s disease at a younger age (before age 65) is a significant risk factor. But new research suggests that a family member’s genetic risk of developing the disease is not static over time. Instead, it shifts according to both the affected relative’s age at onset and the individual’s current age.
The study tracked the development of Alzheimer’s disease among 904 patients and 4,687 family members. A comparison group of 1,525 elderly individuals without dementia and 7,649 family members provided information on Alzheimer’s disease onset among people without an apparent family history of the disease. The highest genetic risk (13 times greater) was seen among people ages 61–63 whose relative developed Alzheimer’s disease in his or her early 60s. Genetic risk was lowest for people age 70 and older whose relative developed Alzheimer’s disease at age 75 or older. Although family members continued to be at risk of Alzheimer’s disease into their 80s, the risk was comparable to that of people without a genetic link.
- Study sheds light on the impact of Alzheimer’s disease on patients’ typical survival time.
Alzheimer’s disease is known to shorten a person’s lifespan. But a new study demonstrates just how much it contributes to mortality and how long the average patient lives with the disease. In a 15-year study reported in the Archives of Neurology, researchers tracked mortality rates and causes of death among 1,670 adults age 65 or older when the study began.
Participants were screened periodically for cognitive status and general physical health. The average age of Alzheimer’s disease symptom onset was 80, and for the group as a whole, the average survival time was 5.9 years. For Alzheimer’s disease patients diagnosed before age 75, average survival time was 8.3 years. Among patients with Alzheimer’s disease diagnosed after age 85, the average survival duration was 3.8 years.
Overall, having Alzheimer’s disease increased mortality by 40%. Among people diagnosed with Alzheimer’s disease, death certificates were most likely to list cause of death as Alzheimer’s disease/dementia, other brain disorders, pneumonia, dehydration, or decubitus ulcers (“bed sores”). Cancer was listed less often for Alzheimer’s disease patients than for people who had not been diagnosed with Alzheimer’s disease. The lower cancer diagnoses may be related to the lack of cancer screening among people who are cognitively impaired.
