• Overview
• Definition
• Incidence, prevalence and trends
• Risk factors
• Health consequences
• Costs
• Contributors

Risk Factors

Risk factors associated with functional decline

A systematic review of 78 longitudinal studies identified 11 main risk factors (listed below) that are associated with functional decline in older people living at home. These studies were carried out in the USA (62 studies); UK (2); other European countries (10) and Asia (4). ¹ The diversity of the constituent studies and different measures used meant that a qualitative review was necessary.

Cognitive impairment

This is strongly associated with functional decline.

Depression

Depressive symptoms are significantly associated with physical decline.

Disease burden (comorbidity)

There are many approaches to measuring comorbidity but, at a simplistic level, a single chronic condition is a significant predictor of future functional decline and the risk increases incrementally up to four or more chronic conditions.

Increased and decreased body mass index

Several studies use body mass index as a proxy marker for nutritional status. This is not a sensitive indicator for nutritional state but both a high and low body mass index are associated with functional decline.

Lower extremity functional limitation

According to the ICF classification there should be some relationship between functional limitations (such as muscle weakness) and disability. The evidence for upper limb limitations being related to disability is inconsistent, however. The evidence is stronger for lower limb limitations, possibly because of a relationship with falls. Multiple falls, not single falls, are related to functional decline, either by virtue of greater disease burden or because of the psychological effects associated with multiple falls. ²

Low frequency of social contacts

There is good evidence that a low level of social activity and low level of social contacts are associated with poor functional outcomes.

Low level of physical activity

Lack of physical activity is independently associated with an increased risk of functional decline. Moderate activity, such as walking, produces favourable outcomes.

No alcohol intake compared with moderate intake

The evidence for impact of alcohol intake is limited by the lack of detailed evaluation in studies. For men at least, however, there is evidence of an association between excess alcohol intake and risk of functional status decline. For both men and women small to moderate alcohol intake protected against future decline in walking.

Poor self perceived health

People with poor self rated health are at greater risk of functional decline.

Smoking

Current or former smoking is a risk factor for functional decline. Current smoking carried a stronger risk.

Sensory impairment

Self reported poor vision is associated with an increased risk of functional decline. Hearing impairment is an exacerbating factor in people with cognitive impairment. In prospective studies, however, there is no clear relationship between hearing loss and functional decline. The tests for hearing impairment may be too crude to be discriminatory. Impairment of vision and hearing can be modified and can interact with other system impairments to significantly increase the severity of the disability. ³

There is no evidence that nutrition and physical environment are modifiable risk factors and further research is needed.

Many of these risk factors for functional decline can potentially be modified, implying that functional limitation in older age can be reduced. There is evidence from prospective observational studies that functional limitations may be dynamic with short term (months) transitions between disability severity states. ⁴ Frail people are more likely to experience transitions and this has been referred to as unstable disability. ⁵ Greater habitual physical activity is an independent predictor for faster and more prolonged recovery from disability. ⁶

Falls and delirium

Declining independence, frailty, and the elderly care syndromes of delirium and falls are closely related. Many of the above risk factors are shared with these components. For example, visual impairment, cognitive impairment, low level of physical activity, and comorbidity are risk factors for both falls and delirium. ^{7 8}

Research into falls and delirium has shown that single risk factor interventions are insufficient for preventing conditions. The evidence based requirement is for an overall reduction in risk factor burden in individual patients. This implies that complex, systematic, individual patient assessments need to be embedded in routine care systems if we are to achieve a population level effect.

The key risk factors for falls in older people are given in Table 1.

Table 1. Personal risk factors for falls in older people

Source: Tinetti ME, et al, 1988 ⁹ ; American Geriatrics Society, et al, 2001. ⁷

The risk of falls increases with the number of acquired risk factors: none, one, two, three, and four or more risk factors are associated with a 12 month risk of falling of 8%, 19%, 32%, 60%, and 78%, respectively. ⁹ Environmental risk factors, such as poor lighting, unsafe bathrooms, and loose carpets, are contributing factors in 44% of falls. ⁹

The quality of the studies and differences in patient populations studied (for example medical and surgical patients) makes it difficult to summarise estimates for the associated risk for each risk factor. Pre-existing cognitive impairment, particularly dementia, is the major risk factor. ⁸ Medications may be the sole precipitant for 12–39% of delirium. ¹⁰

Environmental risk factors for delirium have also been identified and include ¹¹ :

• Number of room changes

• Absence of a clock or watch

• Absence of reading glasses

• Absence of a family member

• Use of restraints (physical or drugs)

• Multiple ward moves.

Multiple ward moves is common in hospital care pathways. ¹²