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Background: Cognition has been related with gait speed in older adults; however, studies involving the oldest age group, where many have mobility disability and cognitive impairment, are few. The aim was to investigate the association between global cognitive function and gait speed in a representative sample of very old people, and whether the association was affected by dementia, and walking aid use.

Method: This cross-sectional study included 1317 participants, mean age 89.4 years, and 68% women, from the Umeå85+/Gerontological Regional Database. Self-paced gait speed was measured over 2.4 m, with or without walking aids, and global cognitive function with the Mini-Mental State Examination (MMSE). The association between cognition and gait speed was analyzed using multiple linear regression and stratified according to dementia. The influence of missing gait speed values was explored using multiple imputation. An interaction analysis was performed to investigate the influence of walking aid use.

Results: In comprehensively adjusted analyses, MMSE associated with gait speed (unstandardized β (β) 0.011 m/s, 95% Confidence Interval [CI] = 0.009, 0.013, p < 0.001) in the total sample. No association was found in people with dementia (β 0.003 m/s, 95%CI = 0.000, 0.006, p = 0.058), until missing gait speed values were compensated for by multiple imputation (β 0.007 m/s, 95% [CI] = 0.002, 0.011, p = 0.002). In interaction analysis the use of walking aids attenuated the association between cognition and gait speed (β − 0.019 m/s, 95%CI = − 0.024, − 0.013, p < 0.001).

Conclusion: Global cognitive function appears to associate with gait speed in very old people. However, in people with dementia selection bias was indicated since unless missing gait speed values were accounted for no association was observed. Walking aid use attenuated cognitive load, which may not apply to walking in daily activities, and requires further investigation.

Improving dementia screening procedures beyond simple assessment of current cognitive performance is timely given the ongoing phenomenon of population aging. A slow or declining gait speed (GS) is a potential early indicator of cognitive decline scarcely investigated in very old people. Here, we investigated the 5-year associations of baseline GS, change in GS, and cognitive function with subsequent dementia development in people aged 85 years and older (n = 296) without dementia at baseline. Declining and a slow baseline GS were associated with higher odds of dementia development after adjusting for confounders (e.g., age, sex, and dependency in activities of daily living) and missing GS values at follow-up. The GS decline was associated with cognitive decline in participants who developed dementia. The results support the potential of GS tests to predict future cognitive decline among community- and nursing home-dwelling very old people.

Introduction: Low physical activity (PA) is a potential risk factor for dementia and cognitive impairment. However, few studies have focused on very old people (aged ≥80 years), the age group with highest prevalence of dementia. The aim was to investigate if PA associated with subsequent dementia, cognitive function, and gait speed (GS), in very old people.

Methods: A population-based survey was conducted in 1999 and followed-up between 2016 and 2019 in participants ≥80 years. Altogether 541 individuals (56.2% women), 64.9 ± 4.2 years of age at baseline participated. Self-rated baseline PA was categorized into low, medium, or high. Cognitive function was assessed with the Mini-Mental State Examination (MMSE), executive function with the Frontal Assessment Battery (FAB), and GS (in meters/second) was measured over 2.4 m at follow-up.

Results: During a mean of 19.0 ± 1.1 years, 175 (32.3%) developed dementia. Low or medium PA compared to high PA did not associate with subsequent dementia, and PA did not associate with future cognitive function (MMSE). PA associated with executive function (FAB) (unstandardized beta [95% confidence interval]) (0.67 [0.07–1.27]), but not after adjustments. PA associated with subsequent GS in the unadjusted model and after adjustment for age, sex, smoking, and education (0.06 [0.02–0.09], and 0.04 [0.01–0.08], respectively), but not after adding adjustment for hypertension, obesity, and glucose intolerance.

Conclusion: No support was found for the hypothesis that low PA is a potential risk factor for dementia in very high age. However, PA and executive function were associated in unadjusted analyses which indicate that PA may be important for at least one aspect of cognitive function. The association between PA and GS around 2 decades later seems attenuated by cardiometabolic risk factors. Future investigations regarding PA, dementia, and cognitive decline may consider cardiometabolic risk factors such as hypertension, obesity, and glucose intolerance, and include repeated measures of PA over the life course.

Background: Physical activity and sedentary behavior vary across the life span, and in very old people activity behavior can vary considerably over 24 h. A physical activity questionnaire adapted for this age group is lacking. This study was conducted to validate such a newly developed questionnaire suitable for use in very old people.

Research question: Is the International Physical Activity Questionnaire adapted for adults aged ≥ 80 years (IPAQ-E 80 +) a valid measure of physical activity in very old people?

Methods: Seventy-six participants (55.3% women) with a mean age of 84.4 ± 3.8 years wore accelerometers for ≥ 5 consecutive days, and completed the IPAQ-E 80 +. Spearman's rho and Bland-Altman plots were used to analyze the validity of IPAQ-E 80 + against accelerometer measures. Analyses were conducted for the separate items sitting, laying down at daytime and nighttime, walking, moderate to vigorous (MV) walking, and moderate to vigorous physical activity (MVPA), and the summary measures: total inactive time, sedentary time (i.e. lying down at daytime + sitting), total active time, and total MVPA + MV walking.

Results: The IPAQ-E 80 + correlated with the accelerometer measures of total inactive- (r = 0.55, p < 0.001), sedentary- (r = 0.28, p = 0.015), walking- (r = 0.54 p < 0.001) and total active- (r = 0.60, p < 0.001) times, but not with measures of intensity of walking or physical activity; MV walking (r = 0.06, p = 0.58), MVPA (r = 0.17, p = 0.13).

Significance: In this study the IPAQ-E 80 + showed fair to substantial correlations with accelerometers, and it therefore seems able to rank very old people according to levels of PA (total inactive-, sedentary-, and total active time, and walking time). The IPAQ-E 80 + seems promising for use in studies investigating associations between activity behavior and health in this population. Further investigation is needed to determine whether the IPAQ-E 80 + can accurately measure PA intensity.