Exercise staves off dementia in older women: Study

By Dr. Ananya Mandal, MDApr 24 2012

Older women with first signs of memory decline might ward off full-blown dementia by engaging in routine strength training according to a new study. However supervised weight-lifting seems to be working better than aerobics-based activity programs, the study found. The study was conducted with researchers from the Department of Psychology and Division of Geriatric Medicine at UBC, and Department of Psychology at the University of Iowa.

“Most studies have looked at aerobic training, but this study compares both aerobic and strength training,” explained study co-author Teresa Liu-Ambrose, an assistant professor in the department of physical therapy at the University of British Columbia. “And among people who don't yet have dementia but are already at a high risk in terms of mild memory and executive function impairment, our study shows that strength training, but not aerobics training, does have benefits for cognition.”

Liu-Ambrose, also an investigator at the university's Center for Hip Health and Mobility and the Brain Research Center, and her colleagues outlined their findings in the April 23 issue of the Archives of Internal Medicine.

The researchers note that dementia is a huge public health concern, with a new case diagnosed somewhere in the world every 7 seconds. Among the elderly, mild “cognitive,” or mental, impairment is viewed as an indicator of future full-blown dementia risk, as well as a chance to perhaps intervene with some form of treatment that might lower that risk.

Previously, the study team found that a year of twice-weekly resistance (strength) classes seemed to boost overall cognitive capacity among mentally healthy elderly women. This time, the team focused on women between 70 and 80 years old who had complained of memory difficulties and were deemed to have “probable” mild cognitive impairment. For six months, the women engaged in 60-minute classes twice a week. The three groups were;

• One group performed an hour of resistance training twice a week. This included lifting weights
• Another performed an hour of aerobic exercise and walked outdoors twice a week
• A third group did a twice-weekly “balance and tone” training sessions. This group was considered the control group

Seventy-seven women completed the program, which included standard verbal and visual memory tests, and decision-making and problem-solving tasks. Almost one-third underwent functional MRI at the start and end of the study to look for brain activity changes.

After 6 months, compared to those in the balance/tone classes, the strength-training group was found to have experienced “significant” cognitive improvement. The strength-training group also experienced activity changes in three specific parts of the brain's cortex associated with cognitive behaviour, the researchers found. These changes were not seen among the balance/tone group. As for the aerobics group, while significant physical improvements were cited relative to the balance/tone group, this group did not appear to accrue the same mental benefits as the strength-training group.

The results showed resistance-training significantly improved executive cognitive functions, associative memory performance, and functional brain plasticity. In contrast to previous studies in healthy older adults, aerobic training did not demonstrate any significant effect for cognitive and brain plasticity. “There is much debate as to whether cognitive function can be improved once there is noticeable impairment,” said Liu-Ambrose, “What our results show is that resistance training can indeed improve both your cognitive performance and your brain function. What is key is that it will improve two processes that are highly sensitive to the effects of aging and neurodegeneration: executive function and associative memory -- often impaired in early stages of Alzheimer's disease.”

The findings might even be conservative, the authors said, because many women skipped classes. The team cautioned that their findings may not necessarily apply to women of a different age group, or to men in general.

Catherine Roe, an assistant professor of neurology at the Washington University School of Medicine in St. Louis, hailed the effort as a “worthwhile avenue of exploration” while also expressing some surprise. “There is certainly other work that has also suggested that exercise can be beneficial cognitively,” she noted. “Participation in physical activity definitely seems to help preserve memory and thinking skills.” On the other hand, Roe said, this study “surprises me, because I can't think of a mechanism off-hand why one (exercise method) would work and not the other.”

To that point, Liu-Ambrose said that for now, her team could only hypothesize. “It could be that resistance-training requires more learning and monitoring by its very nature,” she said. “If you're lifting weights you have to monitor your sets, your reps, you use weight machines and you have to adjust the seat, etc. But with walking it's much more natural for most, so there's less cognitive involvement. But at this point we don't have a clear idea of what's going on at the mechanistic level.”

Liu-Ambrose said that longer-term benefits remain unknown. “But I would say that overall physical activity of this sort is a pretty promising strategy, because it's one of the few interventions that can be delivered globally, and it's pretty inexpensive compared with other approaches.”