Background: Previous research indicates that persons with chronic obstructive pulmonary disease (COPD) and asthma may have more cognitive impairment compared to persons without these diseases. However, there are no previous studies regarding long-term effects of these diseases on the risk of clinically diagnosed mild cognitive impairment (MCI) and dementia. We examined the association between midlife and late-life self-reported COPD and asthma and the lifelong risk of cognitive impairment (MCI/dementia) in a population-based study with a follow-up of over 25 years.
Methods: Cardiovascular Risk Factors, Aging and Dementia (CAIDE) study includes 2000 participants who were randomly selected from four separate, population-based samples originally studied in midlife (1972, 1977, 1982 or 1988). Re-examinations were carried out in 1998 and 2005-8 (N=1511, 75.6 %) during which 172 persons were diagnosed with MCI and 117 with dementia.
Results: Midlife COPD (HR 1.85, 95% CI 1.05 - 3.28), asthma (HR 1.88, 95% CI 0.77 - 4.63) and both pulmonary diseases combined (HR 1.94, 95% CI 1.16 - 3.27) increased the later risk of cognitive impairment even after full adjustments. However, pulmonary diseases diagnosed later in life seemed to be inversely related to cognitive impairment (fully adjusted model for both pulmonary diseases combined HR 0.42, 95% CI 0.19 - 0.93).
Conclusions: In this population-based study, with more than 25 years of follow-up, midlife COPD and asthma were associated with an almost two-fold risk of MCI and dementia later in life. Pulmonary diseases diagnosed later in life seemed to have an inverse relationship with cognitive impairment probably reflecting survival bias.