Although more specific surveys needs to be performed, there is sufficient evidence to state that gait speed identifies autonomous community-dwelling older people at risk of adverse outcomes and can be used as a single-item assessment tool. The assessment at usual pace over 4 meters was the most often used method in literature and might represent a quick, safe, inexpensive and highly reliable instrument to be implemented.

Until recently, clinicians and researchers have performed gait assessments and cognitive assessments separately when evaluating older adults. Increasing evidence from clinical practice, epidemiological studies, and clinical trials shows that gait and cognition are inter-related in older adults. Quantifiable alterations in gait among older adults are associated with falls, dementia, and disability. At the same time, emerging evidence indicates that early disturbances in cognitive processes such as attention, executive function, and working memory are associated with slower gait and gait instability during single and dual-task testing, and that these cognitive disturbances assist in the prediction of future mobility loss, falls, and progression to dementia. This paper reviews the importance of the gait-cognition inter-relationship in aging and presents evidence that gait assessments can provide a window into the understanding of cognitive function and dysfunctions, and fall risk in older people in clinical practice. To this end, the benefits of dual-task gait assessments (e.g., walking while performing an attention-demanding task) as a marker of fall risk are summarized. Further, we also present a potential complementary approach for reducing the risk of falls by improving certain aspects of cognition through both non-pharmacological and pharmacological treatments. Untangling the relationship between early gait disturbances and early cognitive changes may be helpful for identifying older adults at higher risk of experiencing mobility decline, falls and the progression to dementia.

The objective of this study was to systematically review all published articles examining the relationship between the occurrence of falls and changes in gait and attention-demanding task performance whilst dual tasking amongst older adults. An English and French Medline and Cochrane library search ranging from 1997 to 2008 indexed under 'accidental falls', 'aged OR aged, 80 and over', 'dual task', 'dual tasking', 'gait', 'walking', 'fall' and 'falling' was performed. Of 121 selected studies, fifteen met the selection criteria and were included in the final analysis. The fall rate ranged from 11.1% to 50.0% in retrospective studies and from 21.3% to 42.3% in prospective ones. Amongst the three retrospective and eight prospective studies, two and six studies, respectively, showed a significant relationship between changes in gait performance under dual task and history of falls. The predictive value for falling was particularly efficient amongst frail older adults compared with healthy subjects. Two prospective studies challenged the usefulness of the dual-task paradigm as a significant predictor compared to single task performance and three studies even reported that gait changes whilst dual tasking did not predict falls. The pooled odds ratio for falling was 5.3 (95% CI, 3.1-9.1) when subjects had changes in gait or attention-demanding task performance whilst dual tasking. Despite conflicting early reports, changes in performance whilst dual tasking were significantly associated with an increased risk for falling amongst older adults and frail older adults in particular. Description of health status, standardization of test methodology, increase of sample size and longer follow-up intervals will certainly improve the predictive value of dual-task-based fall risk assessment tests.

Although retrospective studies found that the TUG time performance is associated with a past history of falls, its predictive ability for future falls remains limited. In addition, standardization of testing conditions combined with a control of the significant potential confounders (age, female gender and comorbidities) would provide better information about the TUG predictive value for future falls in older adults.

nervous system as a whole, and in particular on the CNS. During cerebral development, vitamin D may act like a neurosteroid hormone in the areas of neurotrans mission, neuroprotection, and neuroimmunomodulation. Moreover, vitamin D deficiency has been associated with neurological and psychiatric disorders. In older adults, hypovitaminosis D has been associated with neuromuscular disorders, dementia, and Parkinson's disease. Thus, vitamin D supplementation might have a protective effect against these neurological disorders. Conclusions: Vitamin D has been associated with many neurological functions and its deficiency with dysfunction. Low serum 25-hydroxyvitamin D concentrations can potentially be reversed. This simple and low-cost correction might contribute to the primo-secondary prevention of various neuropsychiatric disorders.

Lower serum 25OHD concentrations predict executive dysfunctions, especially on mental shifting, information updating and processing speed. The association with episodic memory remains uncertain.

Vitamin D has been investigated in association with cognitive function in older adults. It is unclear whether hypovitaminosis D could be associated with Alzheimer's disease (AD). Our objective was to systematically review and quantitatively synthesize the association of low serum 25-hydroxyvitamin D (25OHD) concentrations with AD in adults. A Medline and PsycINFO® search was conducted on May 2012, with no limit of date, using the MeSH terms "Vitamin D" OR "Hydroxycholecalciferols" combined with the MeSH terms "Alzheimer disease" OR "Dementia" OR "Cognition" OR "Cognition disorders" OR "Memory" OR "Memory Disorders" OR "Executive Function" OR "Attention" OR "Neuropsychological Tests". Of the 284 selected studies, 10 observational studies (including 9 case-controls and 1 cohort study) met the selection criteria. All were of good quality. The number of AD cases ranged from 20 to 211 (40%-100% female). Finally, 7 case-control studies were eligible for fixed and random-effects meta-analyses of bias-corrected effect size of the difference in serum 25OHD concentrations between AD cases and controls using an inverse-variance method. The pooled effect size in random-effects meta-analysis was 1.40 (95% CI: 0.26;2.54), a 'large' effect size that indicates that serum 25OHD concentrations were 1.4 standard deviation units lower in AD cases compared to cognitively healthy controls (p = 0.016). In conclusion, AD cases had lower serum vitamin D concentrations than matched controls. This reinforces the conceptualization of vitamin D as a 'neurosteroid hormone' and as a potential biomarker of AD.

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