Public Health

Alzheimer's Disease (AD) frequently co-occurs with multiple chronic conditions (MCCs). This study aimed to identify specific combinations of MCCs, utilizing detailed ICD-10 groupings to inform targeted prevention strategies.

We analyzed de-identified electronic health records (EHR) of 2,629 AD patients from the University of Iowa Hospitals and Clinics (2015-2021). Patient diagnoses were grouped into their first 3-level ICD-10 codes. The Apriori algorithm was employed to identify co-occurring ICD-10 groups, iteratively analyzing singular, dyad, triad, and tetrad combinations. Support (frequency) and Leverage (correlation) metrics were used to identify significant patterns.

46 common ICD-10 groups were identified. Hypertension (I10; 43.3%), lipoprotein metabolism disorders (E78; 31.5%), major depressive disorder (F33; 23.6%), and diabetes (E11) were the most frequent singular co-occurrences. Hypertension consistently appeared in the most common dyads (e.g., I10-E78: 21.4%, I10-F33: 13.1%, I10-E11: 10.9%), with I10-E78 exhibiting the highest correlation (7.8% more frequent than expected). Other highly correlated dyads included major depression-anxiety (F33-F41; 4.5%) and lipoprotein metabolism-ischemic heart disease (E78-I25; 3.9%). These dyads formed the most common/correlated triads (e.g., I10-E78-F33: 7.7%/4.5%, I10-E78-E11: 6.7%/4.2%, I10-E78-I25: 6.6%/4.5%). Notably, triads involving hypertension-ischemic heart disease (I10-I25) with gastroesophageal (K21), lipoprotein metabolic (E78), and sleep disorders (G47) demonstrated frequencies more than two-fold higher than expected (high correlation). The most common and correlated tetrads included hypertension-lipoprotein metabolism-major depression (I10-E78-F33) with anxiety (F41), gastroesophageal reflux (K21), sleep disorders (G47), and other hypothyroidism (E03), as well as hypertension-lipoprotein metabolism-gastroesophageal reflux-ischemic heart disease (I10-E78-K21-I25).

This study identified highly prevalent and correlated combinations of MCCs in AD patients, including well-established risk factors. These findings have crucial implications for developing targeted disease prevention strategies in this vulnerable population.