Hospital-treated infections, especially repeated infections in early life and midlife, are associated with increased risks for Alzheimer’s and Parkinson’s disease, according to a new study published.

Swedish researchers examined the association between the risk for the three most common neurodegenerative diseases (Alzheimer’s disease, Parkinson’s disease, or amyotrophic lateral sclerosis [ALS]) and prior inpatient or outpatient episodes of hospital-treated infections (1970 to 2016).

For each case (291,941 Alzheimer’s disease cases; 103,919 Parkinson’s disease cases; and 10,161 ALS cases), five controls randomly selected from the general population were matched based on sex and year of birth.

The researchers found that a hospital-treated infection five or more years prior was associated with an increased risk for Alzheimer’s and Parkinson’s disease.