It is increasingly clear that becoming demented as we age is more than just Alzheimer’s disease. There may be few if any “pure” cases of Alzheimer’s disease. It may be the added wear and tear from added medical burdens in conjunction with the pathology of Alzheimer’s that leads to dementia. We already test for factors such as B12 deficiency, thyroid deficiency, and acute infections as they may impact cognitive function and are treatable conditions.

However, we ignore many diseases that may take a toll on brain function and cognition. We are just coming to terms that such events as surgery, treatment of cancer, sleep apnea, and repeated head injuries have short and long term effects on cognition. The cumulative load is too much for biological and psychological compensation with time and aging. One often-ignored disease is lung disease such as COPD (chronic obstructive pulmonary disease) and asthma. Most with these diseases do not become demented but these conditions add to the risk and are often modifiable/treatable (Lung disease as a determinant of cognitive decline and dementia, James Dodd, 2015, Alzheimer’s Research and Therapy, 7, 32 PMID 25798202).

Lung disease increases cognitive impairment and brain pathology. We can add this to a list that includes smoking, cardiovascular disease, depression, physical inactivity, hypertension, diabetes, drugs, sleep disturbance, infections, and social isolation that puts us at risk for cognitive decline and are modifiable by life style and medical management starting at least in middle age. There is an independent association between lung function and cognitive performance.

The two main obstructive lung diseases are COPD and asthma. COPD is the most common lung disease. It is preventable and treatable. If left unchecked it is progressive and involves an inflammatory response to noxious particles or gasses most often secondary to tobacco smoke. Asthma is more frequent in children and young adults and is associated with inflammation and atrophy of lung tissue in response to allergy and hay fever rather than smoking. Treatment with inhaled bronchodilators and steroids improve both lung and cognitive function. Both conditions are often associated with cognitive impairment.

Although the focus of belief has been that hypoxia is the culprit, there is cognitive dysfunction in COPD without hypoxia. More likely the problem stems from cerebral small vessels disease, microbleeds in the brain, chronic inflammation, and oxidative stress. Smoking leads to decreased volume and density of frontal grey matter, risk of stroke, and cerebroatrophy. Finally, COPD has been linked to reduced hippocampal volume – a critical memory structure. In one study half of those with serious acute exacerbations of COPD had moderate to severe cognitive deficits that did not resolve after three months.

We can conclude that lung disease – especially COPD is a modifiable risk factor for cognitive decline and may contribute to the development of dementia. Lung disease independently from Alzheimer’s pathology is linked to memory/cognitive impairment but may or may not be associated with the rate of decline. Finally, the mechanisms for causing brain pathology are very complex.