“Depression was the only comorbidity diagnosed after AD start.”
Several conditions—including hypertension and high cholesterol—appear before a diagnosis of Alzheimer’s disease, while depression typically emerges after, according to a large-scale analysis.
Electronic health records for over 2,500 patients diagnosed with Alzheimer’s were examined, analyzing the timing of 12 common comorbidities relative to diagnosis. The data came from a hospital database covering 2008 to 2019 and was validated using a second, nationwide dataset.
Hypertension was the most common condition preceding Alzheimer’s, appearing approximately 1 year before diagnosis. High cholesterol appeared even earlier—about 1.3 years before diagnosis. Other conditions such as kidney disease, anemia, diabetes, and hypothyroidism were also diagnosed before Alzheimer’s, though the timing varied. Hypothyroidism, for example, appeared just over 1 year prior. Gastrointestinal conditions were among the least frequent.
On average, depression emerged 0.16 years following diagnosis. “Depression was the only comorbidity diagnosed after AD start,” noted Bayard Rogers of the University College London.
Rogers analyzed records from nearly 300,000 patients, of whom approximately 2,500 had Alzheimer’s. Most were women (65.1%) and White (70.8%), with an average age of 81.5 years at diagnosis. A second dataset of over 51,000 participants confirmed similar trends: cardiovascular and metabolic conditions were more common in patients with Alzheimer’s than those without.
Of Alzheimer’s patients in the second dataset, 55% had high cholesterol, compared to 30% in the hospital-based group. Hypertension showed a similar pattern, appearing more frequently in Alzheimer’s patients across both cohorts. Hypertension increased the odds of an Alzheimer’s diagnosis by 11.8%, while high cholesterol increased it by 12.1%. Thyroid disease and diabetes did not significantly raise Alzheimer’s risk despite their prevalence.
"Understanding AD comorbidities is crucial, as they might influence the onset and progression of AD or, alternatively, share common risk factors that contribute to the development of the disease," noted Rogers
Limitations included potential underreporting of earlier diagnoses from outside institutions and the reliance on diagnosis codes rather than biological confirmation of disease. Still, the timing of comorbidities provides insight into Alzheimer’s development and may help identify opportunities for earlier detection or intervention.
Rogers declared no conflicts of interest.