This study is among the first to investigate gait speed (both usual and fast) in a large and representative sample of community-dwelling older adults living in a developing country. Neither usual gait speed nor fast gait speed showed an independent association with any social demographic outcomes (other than age) such as race/ethnicity, income, or educational level, suggesting that health status might be the main contributor to a slower gait speed in this population.
The odds of walking at a slower usual or fast usual speed increase with age. Regarding specific health conditions, urinary incontinence, stroke, and diabetes were the main contributors to a slower usual gait speed, and urinary incontinence largely influenced fast usual gait speed. Older adults with a low perceived self-efficacy manifested by a high concern of falling and a low level of physical activity had higher odds of being in the slower usual gait speed or slower fast gait speed groups.
Comparison with previous studies
The average gait speed at usual pace, mean age, and race/ethnicity characteristics observed in our study were similar to those observed in US studies [2, 34], in which the population showed a mean usual gait speed of 1.12 m/s. The participants’ mean age was 73.6 years, and the population comprised whites (58.5%) and blacks (41.5%). Also, the percentage of individuals with a usual gait speed below 1.0 m/s was quite similar [2, 34]. Two studies [2, 35], which included only men, and another with a European population , showed similar mean gait speed values to those presented in the present study; however, the vast majority of the sample comprised white participants. Interestingly, comparing our results with those obtained in another US study involving only a Hispanic population shows that the difference in mean usual gait speed was substantial (1.11 m/s vs. 0.56 m/s, respectively), and the prevalence of a usual gait speed below 1.0 m/s in this Hispanic population was at least three times higher (95.6%)  than that reported in the present study. We did not observe racial differences in gait speed. However, a recent study  that compared Caucasians and African Americans identified that gait speed was slower in African Americans, even when adjusting for multiple confounders and covariates, such as age, gender, education, comorbidities and pain. One possible explanation is that, in some multiracial samples, such as ours, the ambiguity in racial classification can be substantial , mainly in Brazil where race is based primarily on skin colour rather than ancestry. We overcome part of this problem using a self-classification method instead of an interviewer classification method that has been proven to be less biased by socioeconomic position , however, other factors in our study may have possibly influenced the lack of association between gait speed and race, such as personal and environmental factors.
In previous studies, socioeconomic inequalities such as high financial insecurity levels, low employment and low educational levels were reported as important contributors to reduced gait speed in older adults [23, 24]. These associations were partly explained by differences in health behaviors and incidence of chronic diseases largely explained by physiological measures that have an impact in physical function, particularly related to lower extremity disability among older adults. In addition, our study did not confirm an independent association between socioeconomic status outcomes and gait speed. Lower educational level was crudely associated with slower usual gait speed but this association became non-significant when adjusted by age, mobility-related disorders and fear of falling. Moreover there was a high number of participants in low educational and low-income strata in our sample, which might have attenuated the influence of social disparities in gait speed.
We identified a strong independent association between age and usual and fast gait speeds. The mean age was higher in the slower groups. This finding is corroborated by other studies [1, 2] and can be explained by the adoption of a more conservative basic gait pattern, which is likely to be a compensatory strategy to maintain balance in the presence of age-related deficits in physiological function .
Slow usual gait speed was associated with neuromuscular mobility-related disorders. Diabetes is considered to be a subclinical inflammatory condition that contributes to the aetiology of metabolic and cardiovascular complications, and is associated with sarcopenia , which is an early indicator of functional decline . The literature shows that patients with diabetes walk more slowly and have greater variability in stride length . In addition, older patients with diabetes show abnormal functional balance and mobility-related disabilities, which in turn can compromise gait speed . Stroke is commonly associated with slower cadence, shorter stride length and weakness of hip flexors and knee extensors, which ultimately reduce gait speed [42, 43].
Global cognitive function was crudely associated with slower usual and fast gait speeds, but was not associated in the final regression models. However, studies show a relationship, both cross-sectionally and longitudinally, between gait speed and cognitive function [8, 9]. The lack of association identified in the present study may be explained, in part, by the fact that we excluded those with a severe cognitive decline.
Older adults that are less confident in their balance control tend to change the temporospatial parameters of gait, such as adopting a reduced stride length, and an increased stance width and double support time [44, 45]. It is suggested that older people who are afraid of falling, or have a lower perceived self-efficacy, develop a more hesitant motor control pattern, shifting their control of balance from an automatic fast mode to a more conscious, slow mode, thereby compromising their anticipatory postural adjustments, which might explain why they select a slower gait speed . It is also noteworthy that we found a crude association between gait speed and recurrent falls, highlighting the vicious cycle of falls, fear of falling, and poor physical functioning.
Physical activity level and urinary incontinence were independently associated with a slow usual gait speed and a fast usual gait speed, which suggests a rationale that goes beyond the cumulative effect of certain disease burdens. Older people seem to self-select walking speed according to their functional reserves, and some studies show that more sedentary behaviour compromises maximal oxygen uptake [10, 46] which, in turn, contributes to slow walking speed [1, 47]. Regarding the relationship between urinary incontinence and slower walking speed, we suggest that they might share common physiological pathways, since both activities must rely on good muscular function, which is not only related to strength but also to a proper automatic muscle response that works on a “demand” basis . Other than that, urinary incontinence can be influenced by the perceived self-efficacy for avoiding urine leakage while walking .
This study has limitations imposed by its cross-sectional design, which did not allow us to establish causal links. In addition, the presence of diseases was assessed by self-reporting, which may result in over or under-estimation of disease prevalence. However, we asked participants to report only those conditions diagnosed by a physician; hence, we do not expect that this affected the results substantially. We excluded older adults with severe cognitive decline, and also those with severe neurological conditions, which might limit the external validity of the study. However, we ensured that we covered all the selected census areas and tried to guarantee that all older adults living in the area were interviewed. Additional streets in the same region were selected to compensate for drop-outs and to maintain the cluster sampling.
Considering gait speed as a strong marker of overall health status and mortality in older adults , our current results shows that some interventions that may prevent a decrease in gait speed can be carried out in large populations. These include improvements in physical activity levels. On an individual basis, the assessment of gait speed in specific groups of older people (such as those with neuromuscular mobility-related disorders) may provide useful information that can be used for further comprehensive geriatric assessments. The prevalence of incontinence is increasing in both women and men  and its management in the elderly is frequently neglected, despite its well-known association with poor quality of life and psychological wellbeing. Evidence is accumulating that all conservative management strategies used in younger adults can be used in selected older, motivated people, including life style modifications, pelvic floor muscle training for those with stress incontinence, and bladder retraining for those with urge incontinence . In addition, interventions aimed at reducing activity avoidance by older adults with a high fear of falling may help to prevent associated decreases in gait speed.