A new study, published in the journal Neurology, found that having cancer reduced the risk of developing Alzheimer’s and vice versa.  The researchers studied over one million people in Northern Italy using data from registries and a local health authority.  The study observed the population from 2004 to 2009.  Researchers calculated expected rate of Alzheimer’s in newly diagnosed cancer patients based on age, sex, and incidence rates in the general population.  They performed similar calculations for expected rate of cancer in Alzheimer’s patients.

Looking at the narrower pool of residents with Alzheimer’s or cancer, the researchers studied 25,000 people.  They found that those diagnosed with Alzheimer’s had a 43 percent lower risk of developing cancer and those with cancer had a 35 percent lower risk of developing Alzheimer’s.  The scientists have yet to understand the cause for this inverse relationship.  One hypothesis is that these are related to different pathways of aging, whereby one can result in cancer and the other Alzheimer’s.

Another researcher not involved in this study believes the key is that they are opposing forms of related genetic activity.  Put simplistically, cancer is the over-reproduction of cells that refuse to die and Alzheimer’s is the under-reproduction of cells and cell death that comes too quickly.  This may be related to a single gene involved in cell reproduction or cell death.  One study found that a drug for cancer showed a positive impact on Alzheimer’s patients, which would fit with the hypothesis that these conditions come from the same source, but are opposing expressions of that gene.

According to Surveillance Epidemiology and End Results at the National Cancer Institute, approximately 1.6 million people will be diagnosed with cancer in 2013.  Additionally, in 2013, there will be over 500,000 deaths from cancer.  The median age at the time of cancer diagnosis is 66 and the median age at death is 72.  In comparison, 5.2 million Americans have Alzheimer’s and one-third will die from the condition.  The mortality rate for Alzheimer’s increased between 2000 and 2010, but decreased for all major cancers during the same period.

Chronic conditions become more complicated and detrimental when there is a comorbidity, or a dual diagnosis.  In hospital patients, the Agency for Healthcare Research and Quality found that conditions that commonly came with a secondary diagnosis were hypertension, diabetes mellitus, irregular heartbeat, emphysema or chronic bronchitis, and electrolyte disorders.  Depending on the condition and the individual, certain comorbidities are more likely than others.