A study by researchers at the University of Southern California published in the Archives of General Psychiatry analyzed data on 392 pairs of identical and fraternal twins in Sweden, age 65 and older in which at least one of the twins had been diagnosed with Alzheimer’s disease. The control group consisted of similar twins who did not have the disease.
The conclusion reached by the team was that “inheritance may play a role in nearly 80 percent of cases.” (Reuters) Previous studies have already linked the disease to genetics; however, this new data “confirms the higher estimates that have been suggested previously. The important thing is that no one has had this large a sample before,” said lead author Margaret Gatz.
The sample was 10 times larger than any other group of twins previously studied for the disease.
According to Gatz, the study “does suggest that there is an underlying genetic basis” but she said “this doesn’t mean that environment is not important. Environment may be relevant not only for whether but also for when one gets the disease.” (Reuters)
The study concluded that inheritance was “79 percent in the best fitting (analytical) model with the balance of variation explained by non-shared environmental influences.”