Alzheimer’s disease and other forms of dementia are notoriously difficult to detect and treat, leading researchers to search for novel ways to address them. One of the more common ways of studying such stubborn medical conditions is to look for links to other diseases, some of which may not be obvious. In taking this approach, researchers have discovered that dementia and mild cognitive impairment (MCI) may be related to impaired lung functioning when middle-aged.
Lung Conditions: A Primer
There are a wide variety of lung diseases. For the purposes of this study, researchers focused on lung conditions from two broad categories:
- Restrictive Lung Diseases: These conditions feature a restriction on the ability of the lung(s) to expand. The restriction is typically due to some problem in the tissues that comprise the lungs. Examples include idiopathic pulmonary fibrosis and sarcoidosis (an immune system disease). Restrictive lung diseases are typically progressive (they get worse with time), though some may be curable with treatment.
- Obstructive Lung Diseases: An obstructive lung disease is identified by the presence of some factor that restricts airflow in the lungs. Asthma, cystic fibrosis, and chronic pulmonary obstructive disorders (COPDs) like emphysema and bronchitis are typical examples. The obstruction may make it more difficult to inhale, exhale, or both. Obstructive lung diseases are far more common than the restrictive type.
In all cases, lung diseases result in a decreased ability to get oxygen into the body. Since this function is critical for human health and survival, it was not far-fetched for researchers to theorize that it could also be associated with the development of later conditions, like Alzheimer’s and other forms of dementia.
New Findings From Old Data
This study utilized information that was originally gained during an investigation of atherosclerosis in the late 1980s. By employing modern research techniques, they were able to examine the historical data in search of a potential connection between lung conditions and the development of dementia and MCI. The results showed that both restrictive and obstructive types of lung disease are linked to a higher risk of developing dementia or MCI, but at different rates.
When a restrictive lung disease is present at mid-life (an average age of 54 years), a person has a 58% higher chance of developing dementia or MCI, in comparison to someone without lung disease. The rate drops to a still significant 33% for people with an obstructive lung disease. Additionally, researchers found a connection between dementia and low scores on two common lung tests, one of which measures lung capacity and the other, exhaling power.
Limitations and Future Opportunities
While exciting, these findings have their limitations. The primary issue is that the study did not look at the differences between MCI and dementia in how they relate to lung disease. While some forms of MCI are associated with dementia, the conditions can exist separately. Researchers will need to investigate lung disease in the context of dementia and MCI individually before we can gain a clear understanding of the relationship that was observed in this study.
An additional limitation arises from the use of historical data. Since the original investigation was not designed to study dementia and MCI, there were many cases in which individuals were not screened for the associated symptoms. New studies will overcome this issue by collecting new data from new participants, thus providing us with a better understanding of the relationship, and potentially leading us on a path to new dementia treatments and more effective preventative measures.