Gait speed associated factors in elderly subjects undergoing exams to obtain the driver’s license

Objective to analyze the factors associated with gait speed in elderly subjects undergoing physical and mental fitness tests to obtain a driver’s license. Method a cross-sectional quantitative study conducted in transit agencies. The probabilistic sample included 421 elderly (≥ 60 years old). The study was developed through application of questionnaires and tests that assess the frailty phenotype. For evaluating gait speed, the time spent by each participant to walk a 4.6 meter distance at normal pace on a flat surface was timed. Data were analyzed by using multiple linear regression and the stepwise method. The R statistical program version 3.4.0 was adopted. Results there was a significant association between gait speed and paid work (<0.0000), body mass index (<0.0000), Mini-Mental State Examination (=0.0366), physical frailty (pre-frail =0.0063 and non-frail <0.0000), age (<0.0000), sex (=0.0255), and manual grip strength (<0.0000). Conclusion elderly drivers who do not work, women of advanced age, high body mass index, low score in the Mini-Mental State Examination, low hand grip strength, and frail tend to decrease gait speed and should be a priority of interventions.

The greater number of elderly drivers and risks associated with driving a vehicle clearly demonstrate the need for regularly assessing the status of this activity by considering safety and the elderly's capacity of continuing to drive (4) . According to the current traffic legislation (15) , the ability to drive does not address the elderly's physical conditions, especially of the lower limbs, hence the GS is not measured.
The relevance of the study lies in identifying the factors associated with reduced GS for proposing and implementing preventive strategies directed to modifiable variables in order to assist the elderly with maintaining a safe vehicular driving. Knowledge about the theme may stimulate a new field of action for nursing. Gait speed has also been the target of studies involving elderly people in different contexts (9)(10) in spite of the knowledge shortage on this variable in relation to vehicular driving.
The aim of the present study is to analyze the factors associated with gait speed in elderly subjects undergoing physical and mental fitness tests for vehicular driving.

Method
This is a cross-sectional quantitative study performed at transit agencies accredited for physical and mental fitness tests for vehicular driving.   (16) .
The Mini-Mental State Examination (MMSE) (17) was used for cognitive screening. The educational level was considered for the cut-off points (17) .
The following criteria were adopted to operationalize physical frailty (7) : self-report of fatigue/exhaustion, unintentional weight loss, decreased manual grip strength, reduced GS and decreased physical activity. Seniors with three or more of these characteristics were considered frail; those with one or two characteristics were pre-frail, and the elderly without any of these characteristics were considered as non-frail.
The evaluation of each physical frailty marker is described below. Fatigue/exhaustion was determined by self-reported answers to two questions of the Center for Epidemiological Scale-Depression, and all participants who marked '2' or '3' in any of the questions was classified as frail for this marker (7) .
Unintentional weight loss was assessed by selfreport, and any elderly who reported loss of body weight ≥ 4.5 kilograms in the last twelve months was considered frail for this marker (7) . Hand Grip Strength (HGS) was measured through a JAMAR ® hydraulic hand dynamometer. The average of three tests performed with the dominant hand squeezing to the maximum was considered as the final result.
HGS values were adjusted by sex and BMI. The elderly in the lowest quintile (20%) were considered as frail for this marker (7) . For GS, was measured the time each participant took to walk 4.6 meters at normal gait on a flat surface. The final value was the average time spent to walk this distance for three times sequentially. After adjustment for sex and height, participants with GS values in the lowest quintile (20%) were considered frail for this marker (7) . Physical activity was determined by application of the Minnesota Leisure Time Activities Questionnaire. This instrument has been translated and adapted transculturally into Brazilian Portuguese (18) . This variable was adjusted for sex, and the elderly with values in the lowest quintile (20%) of caloric expenditure in physical activities were characterized as frail for this marker (7) .
In addition to GS, in this study, were evaluated the remaining markers of physical frailty, because the group of elderly individuals classified as frail, pre-frail and non-frail were variables of the study.

Results
In the physical and mental fitness tests to obtain

Discussion
Reduced GS as a marker of frailty was present in 20.4% of the elderly who underwent physical and mental fitness tests to obtain a driver's license. Similar percentages were found in a national study 20.9% (19) , and in an international study 21,9% (20) .
The variables significantly associated to GS were For the elderly, working is an important protection mechanism against depression and disability, helps to maintain well-being, good cognitive functioning and independence in activities of daily living (21) . Staying in the labor market is one of the proposals of the active aging policy. Working is one of the components of the participation pillar, an important element for social bonding, and associated with the elderly's health and well-being (22) .

The relationship between BMI and GS reveals that
increasing BMI values lead to a decrease in GS. This negative influence of BMI increase on GS values shows the unfavorable impact of overweight and obesity on the elderly's physical function.
Studies are unanimous in recognizing that higher BMI values imply worse mobility and slower gait speed in the elderly. High BMI is associated with mobility limitation and poorer performance, as measured by GS (<1 m/s) (23) . High BMI values were associated with slow GS (24) . Furthermore, excessive adiposity also contributes to frailty, especially when it occurs together with decreased muscle mass and/or strength (25) .
As for cognitive impairment, with an increase in the MMSE score, there is an increase in GS. This finding demonstrates the positive effect of cognition on GS. and gait was slower at seven years before the clinical onset of dementia (27) .
The association between slow GS and cognitive decline such as dementia is well documented in the scientific literature. A longitudinal study developed in the United States of America (28) points to reduced GS as a factor that predates cognitive decline. This finding is especially important for directing preventive actions for this population, particularly elderly drivers.
The results for physical frailty demonstrated improvement in GS when the elderly passed from the frail to the pre-frail or non-frail condition. This effect was stronger for non-frail elderly compared to pre-frail elderly.
GS is one of the markers of physical frailty, since the functional aspects affected by the syndrome demand speed of performance (7) . GS is considered a predictor of frailty (29) , indicates physical decline, and is associated with the syndrome (30) .
Age had a negative effect on the elderly's GS. year period (31) . Preserving thigh muscle mass and preventing muscle fat infiltration are important aspects for decreasing age-related declines in GS (32) . An association between muscle weakness measured by grip strength and slow GS was found (37) .
Understanding the relationship between muscle strength and GS is relevant especially because they are interrelated with mobility, and consequently with aging people driving a vehicle. The elderly population mobility decline is closely linked to changes in the muscle strength-speed relationship (38) .
The driving license is necessary, and procedures for its issuance and renewal are varied. In Brazil, the current traffic legislation (39) does not assign specific norms for the elderly, except for the shorter period At national level, the exams to obtain a driver's license do not include tests focused on the lower