Intrinsic risk factors for falls

Falls result from an interaction between intrinsic factors (arising within the patient) and extrinsic factors (medications, environment, assistive devices). Rarely is a fall due to a single factor, and risk rises exponentially as intrinsic factors accumulate.

Intrinsic factors comprise three groups: (i) normal age-related physiological change, (ii) disease-related impairment, and (iii) psychological factors such as fear of falling.

Diminished proprioception from reduced conduction velocity in sensory and motor nerves. Peripheral sensation is the most critical afferent control of standing balance in healthy older people.

Slower righting reflexes and slowed reaction time, so the person cannot recover after a trip.

Increased postural sway, mainly anterior-posterior; both magnitude and velocity of sway increase with age.

Loss of muscle mass (10–40%) with preferential loss of type II (fast twitch) fibres, and prolonged contraction and relaxation time — the basis of sarcopenia.

Stiffer joint capsules and ligaments from cross-linking and loss of elastic fibres in articular cartilage.

Gait changes: gait speed falls 12–16% per decade (up to 20% for maximum gait speed), with reduced step length and increased time in double limb support. Older men develop a flexed, wide-based, short-stepped gait; older women a narrow-based, waddling gait. Feet are not picked up as high, increasing tripping.

Reduced baroreflex sensitivity leading to orthostatic hypotension (about 20% of older persons) and postprandial hypotension.

Impaired dual-tasking. Institutionalised older adults who cannot hold a conversation while walking have a high risk of falls.

Neurological: stroke with residual deficit, Parkinson’s disease (rigidity, freezing, slow gait), cerebellar disease, peripheral neuropathy (diabetes), cervical and lumbar spondylosis with cord or root compression, normal-pressure hydrocephalus, seizure disorder, subdural haematoma or tumour.

Cognitive impairment and dementia. Older adults with cognitive impairment fall at two to eight times the rate of cognitively intact peers, and recurrent falls may be the first presentation of dementia. Delirium is the strongest inpatient association.

Cardiovascular: arrhythmias, aortic stenosis, carotid sinus hypersensitivity, orthostatic and postprandial hypotension, and low cardiac output from heart failure or hypovolaemia.

Musculoskeletal: degenerative joint disease of neck, lumbosacral spine and lower limbs; healed hip and femur fractures causing an unsteady gait; lower extremity weakness and deconditioning from disuse.

Sensory: impaired visual acuity (cataract, glaucoma, retinopathy, poor near vision), impaired hearing, and vestibular disorders. Vision becomes more important as other inputs are lost, so visual loss is disproportionately disabling.

Foot disorders: bunions, calluses, nail disease and joint deformities are common and correctable causes of instability.

Genitourinary: overactive bladder, urge incontinence and nocturia.

Chronic musculoskeletal pain causes antalgic gait and acts as a cognitive distractor forcing dual-tasking; it is associated with falls even after adjusting for analgesic use.

Fear of falling (FoF) is the lack of self-confidence that normal activities can be performed without falling. It is an independent predictor of future falls, and it acts by making the person restrict activity (leading to further deconditioning) and by consuming the cognitive resources needed for gait and balance control.

Also intrinsic in effect are alcohol use, loss of ADL function, low baseline physical activity and previous falls — a previous fall is the single strongest predictor of the next one.