Diseases are often described and studied in isolation, yet there is increasing recognition of the complex interrelatedness of diseases and treatments in patients with multiple chronic diseases. Our objective was to describe the impact of selected diseases involving chronic inflammation (chronic obstructive pulmonary disease [COPD], osteoarthritis, and rheumatoid arthritis) on mortality.
We identified a cohort aged 55 to 64 years with one or more chronic conditions. Clusters of mutually exclusive disease combinations were created. Five-year all-cause mortality was determined and the relative risk (RR) of mortality was estimated when COPD, osteoarthritis, and rheumatoid arthritis were added to clusters.
In 741,847 persons the 5-year mortality rates were lowest among persons with one condition and increased with more chronic conditions. The presence of osteoarthritis in a cluster was an exception where the risk was lower compared with that cluster without osteoarthritis: COPD (RR = 0.73 [95% confidence interval (CI), 0.65, 0.81]); ischemic heart disease (0.63 [0.52, 0.76]); hypertension (0.77 [0.71, 0.83]); dementia (0.63 [0.42, 0.93]); depression (0.65 [0.50, 0.84]); hypertension plus diabetes (0.85 [0.77, 0.93]); and ischemic heart disease plus hypertension (0.83 [0.73, 0.94]).
The association between osteoarthritis and lower rates of mortality is notable and replicating these findings to explore causal relationships is important.