
A decade after researchers in Taiwan discovered a strong link between asthma and Alzheimer’s disease (AD) in its residents, an American university released the results of a similar study in the U.S.
Researchers at the University of Wisconsin School of Medicine and Public Health in Madison reported that asthma was associated with a 20% to 33% higher, two-year incidence of Alzheimer’s disease. Their study, “Alzheimer Incidence and Prevalence With and Without Asthma: A Medicare Cohort Study,” was published in The Journal of Allergy and Clinical Immunology. According to lead author, Christie Bartels, MD, MS, division head and associate professor for the university’s division of rheumatology in the department of medicine, the U.S. study was prompted by the results of the 2014 Taiwanese study, “Risk of Dementia Among Patients With Asthma: A Nationwide Longitudinal Study."
Christie Bartels, MD, MS
Researchers used a 20% random sample from a national Medicare database from the same period (between 2013 and 2015). They compared adult patients with asthma to those without asthma who were both on more than 12 months of continuous Medicare. Asthma was defined by the presence of one inpatient or two outpatient codes for the condition. The primary outcome of the study was a two-year incident or prevalence of AD.
The cohort included slightly more than 5.4 million Medicare beneficiaries representing a mean age of 69.6 years. Of that, 678,730 individuals had baseline asthma. The asthma patients more often identified as Black and as having prior Medicaid eligibility compared to patients without asthma. They were also more likely to live in disadvantaged neighborhoods, have cardiovascular disease and comorbidity.
The overall prevalence of AD in asthma patients was 7.8% compared to patients without asthma at 5.4%. Among patients with asthma, the prevalence of dementia was 20.3% compared with 12.9% in patients without asthma.
“The magnitude of observed increases in Alzheimer’s in asthma even after controlling basic sociodemographics was surprising,” Dr. Bartels said. “We observed an approximately 30% increased incidence and nearly 50% greater prevalence of Alzheimer’s in asthma among five million U.S. Medicare patients.”
Dr. Bartels also said that some studies have found rheumatoid arthritis is linked to an increased risk for AD, whereas treating this condition with anti-TNF agents is linked to a decreased risk. This, in addition to the study’s findings, raises questions of whether biologic treatment of asthma could mitigate risk for AD.
“Combining our findings with prior reports in [rheumatoid arthritis], one could hypothesize that controlling inflammation aggressively and using steroid-sparing therapies might reduce Alzheimer’s risk,” Dr. Bartels said.