present at various stages during the course of their illness with different health and economic consequences.

Chronic illnesses can be characterized by the stage (i.e., clinical severity), pattern (i.e., continuous versus intermittent symptoms), and anticipated course (i.e., stable, fixed deficit versus progressive). Because the stage of the condition has the largest impact on health and social consequences, we have organized this section around condition stages.

Early-Stage Chronic Illnesses

We define early-stage chronic illnesses as ones that cause little or no functional impairment and impose a low burden on others. This often characterizes certain chronic illnesses early after their diagnosis or in their uncomplicated stages. For example, such illnesses as benign prostatic hypertrophy (BPH) or early Parkinson’s disease have mild symptoms and burden. Some chronic early-stage illnesses, such as uncomplicated diabetes or New York Heart Association stage I (i.e., individuals with heart disease with no physical limitations) or II heart failure (i.e., individuals with heart disease with slight physical activity limitations), although associated with low functional impairment and burden to others, are associated with a high self-management burden (e.g., the need to monitor sodium and fluid intake and daily weight in heart failure, the need for self-monitoring of blood glucose in diabetes). Other early-stage chronic illnesses, such as mild asthma or osteoarthritis, may cause physical symptoms and functional limitation only intermittently, with asymptomatic periods in between, requiring a low to moderate degree of self-management.

Moderate-Stage Chronic Illnesses

Moderate-stage illnesses can be characterized by moderate, as opposed to low, degree of functional impairment and disability and moderate to high self-management and caregiver burden. At this stage, symptoms often interfere with usual lifestyles. Examples include painful hip or knee osteoarthritis and stage 2 or 3 Parkinson’s disease.

Several illnesses are associated with disabling episodic flares, although they may have low burden between flares. They are distinguished from early-stage illnesses following this pattern in that they cause moderate to severe, episodic disability (e.g., hospitalization for a flare of COPD), increased self-management and caregiver burden, and moderate to high economic impact. COPD, rheumatoid arthritis, depression, and migraine headache are conditions that often follow this pattern. Some people with complicated diabetes may have functional impairment due to peripheral neuropathy or a lower extremity amputation yet remain stable for some years, despite high

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