Sensory and cognitive functions, gait ability and functionality of older adults*

Objective: to know the relationship between the sensory function, gait ability, and cognitive function with dependency in older adults. Method: a descriptive cross-sectional design, 146 older adults took part. Measurements: Snellen chart, Audiometer, Stereognosia tests, Semmes-Weinstein monofilament, basic aromas and flavors, GAITRite system, Montreal Cognitive Assessment Test, the Barthel Index, and the Lawton and Brody Index. Results: sensory function, cognitive function and gait explain 25% dependence on basic activities of daily life and 21% dependence on instrumental activities of daily life. The variables that influence dependence on basic activities were taste (p=.029), gait speed (p=.009), cadence (p=.002) and step length (p=.001) and, in instrumental activities, gait speed (p=.049), cadence (p=.028) and step length (p=.010). Conclusion: gait speed, cadence and stride length are variables that influence both dependence on basic and instrumental activities of daily life.


Introduction
As age increases, changes arise at the biological level, among which are the decrease in sensory functions, gait ability and cognitive function; these changes become a limitation of the functionality of the older adult that leads them to dependency to carry out basic activities of daily life (BADLs) (1) . Some authors report that, in Mexico, between 26.9% and 30.9% of the older adults are dependent (2)(3) . These data highlight the vulnerability of older adults and the care they require.
The study of dependency in older adults is an important topic, which the nursing professionals should pay attention to, since if it is not properly cared for it can have important individual and family consequences.
Among the individual consequences, the quality of life of the older adult stands out and the need for specialized care may arise; at the family level, family dynamics are altered and an increase in physical, emotional and spiritual overload, and in economic expenses (4)(5) .
The factors associated with dependency are being older, polypharmacy and sedentary lifestyle (6) . On the other hand, research studies have been identified that relate vision and hearing problems, as well as taste, smell and touch with dependency (3,7) . However, no studies have been identified that jointly evaluate the relationship of each of the senses with this variable.
On the other hand, it has been found that there is a relationship between the decrease in gait capacity with dependency, since when there are problems in moving from one place to another, it is not possible to adequately perform the BADLs (8) .
Regarding the decrease in the cognitive function, like functional alterations, it has been observed that this is generally manifested by the same aging process (9) , or due to the presence of diseases, it has been shown that, at an older age, cognitive problems increase, and these increase if the adult suffers from two or more chronic diseases (10)(11) ; regarding functionality, the literature shows a relationship between cognitive functionality and physical functionality, including gait. Some authors report that poor cognitive performance may be a precursor of the functional limitations that lead to disability (12)(13) . Memory-related diseases such as dementia or Alzheimer's, lung disease and arthritis are associated with difficulties in physical functionality and decreased gait speed independently if they occur alone or in combination with other diseases (11,14) .
The studies reviewed on risk factors for dependency in older adults address variables such as age, schooling, smoking, and alcoholism; but very few address the sensory function. For this reason, the objective was to know the relationship between sensory function, gait ability, and cognitive function with dependence in older adults. The information obtained will help guide the areas in which nursing actions can be designed to prevent or delay dependency as much as possible.

Method
A descriptive cross-sectional study was carried out, older adults residing in the urban area, adjacent to a health center belonging to the Health Secretariat of Monterrey, Nuevo León, Mexico, were recruited; the recruitment period was from January to May 2016. The participants were adults 60 years old or older, and the following were considered as inclusion criteria: older adults with the ability to walk, listen and answer the interviewer. The sample consisted of 146 older adults, calculated with the n-Queryadvisor 4.0 statistical package for a correlation coefficient with an effect size of r=.14, a power of 90%, and a significance of .05. The sampling was non-probabilistic with the snowball technique.
Visual, auditory, tactile, olfactory and gustatory acuity were assessed for the sensory function. In people who know how to read, visual acuity was measured with the Snellen Chart of letters and, in those who were not, the Snellen chart with drawings was used. The chart was placed at a distance of 6 m from the participant.
Normal vision was considered when the parameters were 20/15 or 20/20 and abnormal, when they did not achieve those figures. Hearing acuity was measured with a WelchAllyn 232 TM Manual Audiometer. The older adult was asked to indicate when they heard a sound.
It was considered normal when the subject indicated listening between -10 dB and 26 dB and with alteration when it was higher. A higher score represents greater hearing impairment.
The acuity of touch was measured through discriminatory sensitivity, the stereognosia test was performed, which measures the person's ability to identify an object. The participant was put on a mask to prevent him from seeing and later a key was placed The total points perceived by the subject (0 to 10) were considered, where a higher score was rated with greater sensitivity (15)(16) . This test has shown a Kappa reproducibility of .76 to .96, a sensitivity between www.eerp.usp.br/rlae 3 Duran-Badillo T, Salazar-González BC, Cruz-Quevedo JE, Sánchez-Alejo EJ, Gutierrez-Sanchez G, Hernández-Cortés PL.
The olfactory and gustatory acuity was measured with the test of aromas and basic tastes with the Caul selection method, respectively, both proposed by the sensory laboratory of the Agronomy School of the Autonomous University of Nuevo León. For olfactory acuity, 2 g of previously ground ingredients (cumin, pepper, anise, cinnamon and rosemary) were placed in containers; the substances were covered with cotton and the containers were labeled with the corresponding name. The same substances were placed in other containers and the containers were labeled with codes.
The subject was instructed to smell from left to right each substance labeled with names and to memorize the aroma, later he was given to smell coffee to neutralize the aromas and was asked to smell those found in the coded containers and say what substance it corresponded to. A summation of the aromas was distinguished, the higher the score was considered the better olfactory acuity.
Taste acuity measures the ability to recognize four basic tastes (sweet, salty, sour, and bitter). This system reports a reliability for its measurement of 0.91 to 0.99 (19) . Gait speed, width, step length and cadence were considered.
The Montreal Cognitive Assessment Test (MoCA) (20) was used to measure cognitive decline, which allows examining the cognitive functions. MoCA examines different cognitive abilities through reagents with assigned scores for the criteria to be met in each of them.
The reagents and scores are the following: visuospatial/ executive level (5 points), identification (3 points), attention (6 points), language (3 points), abstraction (2 points), delayed memory (5 points), and orientation (6 points). The points obtained in each of the skills evaluated must be added together, a score equal to or greater than 26 corresponds to a normal individual, and a lower score classifies it with mild cognitive impairment. The MoCA test has recently been used in the Mexican population (21) , was translated into Spanish and reported a Cronbach's alpha of 0.76 (22) , the Cronbach's alpha obtained in this study was .80.

Functionality was measured with the Barthel
Index for dependency on basic activities of daily living (BADLs), with a Cronbach's alpha of .86-.92 (23) and with the Lawton and Brody Index for dependency on instrumental activities of daily living (IADLs), with a Cronbach's alpha of 0.78, and an intraclass reliability of 0.95 (24)(25)    In Table 3, the correlation coefficient showed a positive association between gait speed and step length with the BADLs, and between gait speed, cadence and step length with the IADLs, and a negative association between step width and the IADLs. A positive association was identified between the cognitive function and the BADLs and IADLs.

Discussion
In the present study it was found that the dependence for the BADLs is different in older adults with and without alteration of visual acuity, a finding which is consistent with an article on a Mexican population (3) . This is consistent in populations of foreign countries; in Tokyo and Georgia, a study was carried out to find out the predictors of dependency and it was found that vision predicts in up to 60% the alteration in functionality (26) , this is why the evaluation of visual acuity must be present in the medical evaluations that are carried out on older adults to correct the alteration as much as possible and avoid dependencies due to this cause. Likewise, it was observed that the dependence for the BADLs and the IADLs is different in the subjects with and without alteration of the tactile acuity in the feet, this takes coherence since both activities include performing displacement actions (gait, climbing stairs) which are affected when somatic sensory changes occur (7) . It would be worth assessing these variables in adults with pathologies that alter the CNS, such as diabetes, for example.
In the search for differences regarding the dependence to perform the BADLs in older adults with and without alteration of auditory acuity, no statistically significant differences were found (26) . This may be because, for the activities of daily life, they focus on mobility that needs coordination and proprioception, which requires vision and balance and not so much that the ability to walk is related to the dependence to perform the ADLs (7,(28)(29) . In this sense, it has been reported that older adults with slow gait speed have greater difficulty in performing the ADLs (8) . This happens because, as a consequence of aging, there are changes in the systems, such as the nervous, skeletal, visual, vestibular and proprioceptive systems, which intervene with postural control and gait, which causes alteration of functionality and leads to dependency (30) .
Another finding was that the lower the cognitive function, the greater the dependency to perform the BADLs and the IADLs. The above explains that, when mild cognitive impairment occurs, in older adults independence is altered to carry out daily activities, this is due to the alteration in simple and complex cognitive processes that prevents the interpretation of stimuli to turn them into a response (31)(32) .
Older adults with normal visual acuity in the test with and without glasses, presented greater cognitive function. Likewise, older adults with normal gustatory and auditory acuity had a better cognitive function.
The significance found between auditory acuity and cognitive function agrees with that reported by other authors (33)(34)(35)(36)(37) . The findings of the present study confirm what is established in the literature, where it is indicated that there is a relationship between taste and smell with cognitive function (38) .
Older adults with normal visual acuity in the test without glasses, presented higher gait speed and step length, compared to those who presented visual acuity with alteration, gait alterations often presented by visual and vestibular deficits (39) . Older adults with normal tactile acuity had better step length and width, and those with normal hearing acuity had better gait speed and step length. This relationship arises because the main components of gait are balance and locomotion, which depend on vestibular and somatic sensory input, that is, sight, hearing and touch (5,(28)(29) .
Older adults with higher gait speed, longer length and shorter gait width resulted in greater cognitive function, these findings are consistent with that reported by other authors who show statistically significant association between gait speed and stride length with executive (40) ; likewise, in a review of the literature they report that there is an association between gait and cognition in older adults (41) . Along these same lines, the literature shows that proprioceptive input is required to execute the gait process (7,(28)(29) , where the brain receives information on the position and movement of the different parts of the body involved in the gait.
Therefore, the above explains that the gait parameters are altered when deterioration of simple and complex cognitive processes occurs.
Finally, multivariate regression analysis showed that taste, gait speed, cadence, and step length affect the performance of the BADLs, and speed, cadence, and step length affect dependence on performing the IADLs. In the Roper, Logan and Tierney Nursing Model (42) it is stated that there are different factors that influence dependency, among which is the biological factor that includes aging, sensory function, gait ability and cognitive function, which is supported by the findings in the present, therefore, it is considered necessary that in the evaluation of the elderly the sensory function, gait and cognition are considered.
The study provides evidence on sensory functions such

Conclusion
Taste, gait speed, cadence, and step length were found to affect independence/dependency for performing the BADLs; and speed, cadence, and step length affect dependency for performing the IADLs.
Therefore, older adults with greater affectation have a higher dependency risk.