What causes disability in someone?

What Causes Disability

Disability results from impairments—physical or mental abnormalities at the tissue/organ level—that restrict a person's ability to perform normal activities, with the most common causes being lower-body functional limitations, chronic diseases (particularly diabetes and cardiovascular conditions), neurological disorders, and musculoskeletal problems. 1

Definition and Framework

Disability is formally defined as any restriction or lack of ability to perform an activity in the manner or within the range considered normal for a human being, resulting from an impairment. 1 This represents problems at the whole-person level, such as inability to walk or dress independently, which stems from underlying tissue and organ dysfunction. 1

Primary Causes of Disability

Metabolic and Chronic Diseases

• Diabetes is associated with a 50-80% increased risk of physical disability compared to people without diabetes, making it one of the strongest disease-related risk factors for functional impairment. 1
• Lower-body functional limitation is the most prevalent disability among people with diabetes, affecting 47-84% of this population. 1
• Diabetes increases the risk of:
  • Mobility disability by 71% (odds ratio 1.71) 1
  • Instrumental activities of daily living (IADL) disability by 65% (odds ratio 1.65) 1
  • Activities of daily living (ADL) disability by 82% (odds ratio 1.82) 1

Neurological Conditions

• Diabetic peripheral neuropathy impairs postural balance and gait kinematics, leading directly to functional disability and potentially debilitating neuropathic complications. 1
• Stroke (both right- and left-sided lesions) and traumatic brain injuries are major causes of disability requiring rehabilitation. 1
• Chronic neurological disorders including Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis progressively disable patients. 1
• Spinal cord pathology (myelopathy, radiculopathy, spinal stenosis, and spinal cord injury) causes significant functional impairment. 1

Musculoskeletal Disorders

• Knee osteoarthritis results in disabling symptoms in an estimated 10% of people older than 55 years, with a quarter of those severely disabled. 1
• The risk of disability from knee osteoarthritis alone is as great as that from cardiac disease and greater than any other medical disorder in the elderly. 1
• Hip, arm, or vertebral fractures cause disability requiring rehabilitation. 1
• Arthritis with impaired mobility of major joints (back, knees, hips, shoulders) is a common disabling condition. 1

Cardiovascular and Pulmonary Disease

• Ischemic heart disease and chronic lung disease requiring cardiopulmonary rehabilitation are significant causes of disability. 1
• Cerebrovascular disease and vascular cognitive impairment contribute to functional decline, particularly when associated with hypertension and aging. 2

Deconditioning and Immobilization

• Disabilities can be caused or aggravated by immobilization, inactivity, deconditioning, restricted activities, or malnutrition—these are often preventable or reversible causes. 1

Mechanisms Leading to Disability

Biological Aging Processes

• Multimorbidity (the number of coexisting diseases) is the strongest risk factor for disability, as it reflects accelerated biological aging and loss of resilience. 1
• The hallmarks of aging—including genomic instability, cellular senescence, and loss of homeostatic mechanisms—drive the rate of biological aging and increase susceptibility to diseases that cause disability. 1
• Failure in the network of homeostatic mechanisms affects the pace of aging and causes growing susceptibility to diseases, with the resulting multimorbidity being a major cause of disability. 1

Cognitive Impairment

• Depression is among the leading causes of disability in persons 15 years and older, affecting quality of life and functional capacity. 1
• Cognitive decline and dementia, particularly when associated with diabetes or cerebrovascular disease, contribute significantly to functional disability. 1

Clinical Assessment Approach

An assessment of disability should be performed at each visit for people with chronic conditions. 1 When disability impacts functional ability or capacity to manage health conditions, referral to appropriate specialists (physical medicine and rehabilitation physician, physical therapist, occupational therapist, or speech-language pathologist) is indicated. 1

The capacity to accomplish activities of daily living (ADLs) and instrumental activities of daily living (IADLs)—comprising basic and complex life care tasks respectively—serves as the most important measure of functional status. 1

Common Pitfalls

• Do not overlook lower-body functional limitations, as these are the most prevalent form of disability and often the earliest manifestation of functional decline. 1
• Avoid attributing disability solely to aging when treatable underlying conditions (diabetes, neuropathy, deconditioning, depression) may be the actual cause. 1
• Do not neglect the role of multimorbidity—the cumulative burden of multiple conditions, rather than any single disease, is often the primary driver of disability. 1