Physical activity programs tended to influence ADL performance positively. Thus, the decline in ADL performance in demented subjects may be due not only to disease progression but also to physical inactivity . One study showed that the effect on ADL performance disappeared after cessation of the physical activity programs . This observation may explain why three [23, 24, 26] out of five trials showed a significant effect on ADL performance, but only one reported clinically meaningful results despite differences in their physical activity programs . The negative evolution of ADL performance in all control groups except one  tends to support the relationship between physical activity and functional abilities . The most severe ADL degradation was observed in the study which included the patients with the lowest MMSE scores . Delaying ADL deterioration in nursing home residents with moderate or severe cognitive impairment through a physical activity program may be both clinically and economically relevant as ADL care in this patient group accounts for two thirds of the total care time .
The descriptive results were supported by our meta-analyses and allowed us to conclude—as Forbes et al.  did—that even if the proposed treatments have not proven their efficiency in improving the ADL status of the patients, they could nevertheless limit the decline in ADL functioning.
However, the physical activity programs varied among the included studies. In line with Yu and Kolanowski  as well as Taylor et al. , we confirm that there are no clinical practice guidelines for aerobic exercises for persons with dementia. Reasons for the lack of both studies on the matter and practice guidelines may include the individual variability of the aging process and the limitation of physical activity practice due to the disabilities of the very old . Nonetheless, endurance can positively influence the physiological aging process of the cardiovascular system at a central and peripheral level . Aging per se causes loss of muscle strength, and regular strengthening exercises can counteract to some degree this loss in the very old . Based on this knowledge, the content of the physical activity programs covering endurance, gait, and strength training proposed in the included studies seemed to be appropriate.
Questions related to the duration and intensity of the physical activity program, the duration of each session, or their frequency remain unanswered. One high-quality study applied a physical activity program with moderate to high intensity and showed a significant delay of ADL decline only after 12 months duration, but not after 6 months . A high intensity strengthening program during 3 months achieved a similar result in dementia nursing home residents . Paterson and Warburton  suggest that the intensity of physical activity should be at least moderate in order to improve ADL performance in the elderly. The literature on the topic does not either give clear indications on how long an ideal activity program should last. Our review lists programs lasting from 7 weeks to 12 months. Yu and Kolanowski , based on their summary of current knowledge concerning the prevention of Alzheimer’s disease, suggest an ideal program duration of 2 months and the ideal session frequency of three times per week for an aerobic exercise program designed for a medically stable population with dementia and aimed at improving their ADL performance. The most important parameter was regularity of exercising  with high exercise adherence significantly preventing ADL decrease. However, none of the studies investigated long-term effects on ADL performances. The result of the study of Littbrand et al. including residents with less severe dementia showed no lasting effect of physical activity training on ADL . Demented people are likely to need some encouragement to stay physically active and to slow the decrease of their ADL performance  especially in those with moderate to severe dementia. Overall, the optimal frequency and intensity of physical activities which provide a satisfactory long-term effect are still unknown and their determination highly relevant.
Physical activity programs were accompanied by music in only three studies [24, 25, 27], although there is a growing body of evidence that music in advanced stages of dementia could help improve the performance of patients [33, 34]. According to a qualitative study, demented patients claimed that programs should respond to their psychological and social needs, whereas their caregivers considered maintenance of functional independence as the most important goal . Thus, physical activity in groups accompanied by music could more easily respond to the expectations of demented patients and increase their adherence to a physical activity program. In addition, a further criterion to respect is the meaningfulness of the proposed activities. These activities increase adherence in physical activity programs among the elderly .
Information regarding the group sizes was missing. The reduced communication skills, the frailty of this population, and the increased risk of falling may require limited group sizes. An individual approach, as opposed to group sessions, allows meeting a patient’s needs more specifically as community-dwelling participants may prefer exercising at home . The need for individual adaptation of physical activity programs has been stressed by Yu and Kolanowski  as patients with moderate to severe dementia do not express reliably exertion and need guidance to exercise at the targeted level. Variability in content and modalities of physical activity programs (session frequency and duration) impede any precise recommendation for clinical practice.
The variety of applied ADL assessment tools hampered comparison of the program effect on the ADL performance across all studies. Any recommendation to use objective measurement tools for moderately to severely demented subjects was altogether missing from the literature. The Katz Index  is a clinically relevant measurement . However, it has little or no sensitivity to small changes  and is therefore inappropriate for longitudinal studies. Only one study applied a population specific measure, i.e., the Changes in Advanced Dementia Scale , to assess ADL performance in demented persons . The reliability and criterion validity of the Changes in Advanced Dementia Scale are promising . Contrary to other tools, it considers a patient’s mobility. Assessing mobility is crucial as it is a key capacity among elderly with moderate to severe dementia . Mobile patients decrease caregiver burden , and their quality of life may be better . The majority of items in the Changes in Advanced Dementia Scale deal with cognitive abilities to perform ADL and not physical abilities . However, while physical activity programs act primarily on motor tasks, they may also have an impact on cognition . Given the preponderance of items related to cognition, physical components of ADL capacities may be underestimated when applying the Changes in Advanced Dementia Scale. The preceding considerations may explain the clinicians’ and researchers’ difficulties in selecting the appropriate ADL assessment tool.
Safety was an explicit issue in only two studies [23, 25]. Higher levels of physical activity were beneficial and decreased the number of falls in a mildly to moderately demented population . No study reported serious adverse events related to physical activity, but Steinberg et al.  found trends of poorer quality of life and increased depression in their exercise group and discussed the possibility that physical activity may cause distress. However, the finding of higher depression scores was not corroborated by other studies [43, 44].
Several limitations call for a cautious interpretation of the findings reported in the reviewed studies. The methodological quality of the majority of the included studies is low, and information regarding the reliability, validity, and sensitivity to change (i.e., the clinically minimal important change) of the various assessment tools applied to a moderate or severely demented population is missing.
The scores obtained for external validity were low which limits the generalizability of the results and the formulation of recommendations. Internal validity biases reduce confidence in the results. Biases were due to inappropriate randomization methods in four out of the five included studies [23, 24, 26, 27], to the lack of blinding of the outcome assessors in three studies [24, 26, 27] and two studies [23, 26] used ADL assessment tools which were not validated for the moderately and severely demented. The clinical importance of the results was threatened by the insufficient power of three out of the five included studies [23, 26, 27]. The absence of interventions for the control group in two trials [25, 26] represented a further weakness and prevented interpretation of the impact of physical activity programs on ADL in these studies.
The small number of studies corresponding to the selection criteria of our review represents an important limitation of this paper. Although we tried to identify all significant studies, we do not pretend to have conducted a comprehensive review. Defining dementia severity using mean MMSE scores was a pragmatic decision as MMSE scores are the most frequently reported severity measures. However, although populations were described as being moderately to severely demented in the included studies, not all authors reported dementia severity scores [24, 27]. We are aware of the confounding education levels by interpreting MMSE scores  as well as the questionability of the cutoff scores which define moderate and severe dementia . While a uniform definition of severity is still lacking [47, 48], the relevant MMSE scores are still debated . We based our decisions on Tombaugh and McIntyre  and Feldman and Woodward . Harrell et al.  developed a MMSE version which is adapted to severe dementia. However, none of the studies applied it .