Poor lung function tied to higher dementia risk
Having lung disease in middle age was associated with an increased risk of developing mild cognitive impairment (MCI) or dementia later in life, the ARIC* study suggests.
Among the 5,889 participants with data on spirometry test and neurocognitive exam available, those with restrictive lung disease had 58 percent higher risk of developing MCI or dementia over 27 years of follow-up compared with those without lung disease or respiratory symptoms (adjusted odds ratio [OR], 1.58, 95 percent confidence interval [CI],1.15–2.19). [Am J Respir Crit Care Med 2018;doi:10.1164/rccm.201807-1220OC]
Similarly, the risk of MCI or dementia was also greater in participants with obstructive lung disease than those without, although the magnitude of association was smaller than that seen with restrictive lung disease (OR, 1.29, 95 percent CI, 1.05–1.59).
The researchers found that midlife lung disease was associated with dementia or MCI through both Alzheimer’s disease-related dementia (ORs, 1.79 and 1.24 for restrictive and obstructive lung disease, respectively) and cerebrovascular aetiologies (ORs, 1.60 and 1.33, respectively).
Furthermore, restricting the analyses to nonsmokers did not change the findings (OR, 1.69 and 1.72 for restrictive and obstructive lung disease, respectively).
“This enhances aetiological understanding – as it suggests that impaired lung function is linked to dementia and MCI risk independent of smoking and smoking-related confounders,” said the researchers.
Participants with impaired lung function, as indicated by low FEV1** percent predicted (OR, 1.27, 95 percent CI, 1.05–1.54) and FVC*** percent predicted (OR, 1.25, 95 percent CI, 1.04–1.51) had a greater risk of developing MCI or dementia compared with those in the highest quartile of FEV1 or FVC percent predicted.
“If the observed associations are causal, policy and public health efforts to reduce smoking and improve air quality may have the added benefit of preventing the development of dementia and MCI,” the researchers suggested.
“Poor lung health, which is often preventable, may be linked to a greater risk of developing dementia,” they added. “Given the high prevalence of [dementia and MCI], even a modest reduction in risk factors could reduce the societal burden of [these conditions].”
The prospective cohort study followed 14,184 participants (mean age 54.2 years, 55.3 female) for a median duration of 23 years from the ARIC study who underwent spirometry. Forty-two percent of the participants (n=5,889) who completed a comprehensive neurocognitive exam were included in the analysis using adjudicated outcomes.
“Since both all-cause and AD-type dementia have a long natural history … the prospective evaluation of midlife lung health and dementia risk more than 20 years later … [is] an important strength of this study,” the researchers pointed out.
Proposing on plausible explanations for mechanisms mediating the associations, the researchers explained that chronic low blood oxygen levels arising from lung disease can lead to inflammation, physiological stress and damage to blood vessels in the brain.