Almost 10% of U.S. adults 65 and older have dementia. Another 22% have mild cognitive impairment (MCI), which is strongly associated with the development of dementia at a more advanced age. The rate of dementia increases to 35% among people in their 90s. In 2022, the economic costs of these impairments were estimated to be $257 billion per year in the U.S. and $800 billion worldwide. In an attempt to attenuate the human and financial costs, various lifestyle interventions have been studied. Aerobic or cardiovascular exercise has inconsistent success in reducing the effects of MCI in subjects. Given the efficacy of progressive resistance training (PRT) in producing positive health outcomes for cardiovascular disease, mobility impairment/falls, osteoporosis, and depression, the current study investigates the effect of PRT on the behavioral symptoms of MCI and well as the well-documented degeneration of some regions of the brain.

The current study is the first intervention study to investigate the effect of PRT on MCI. Research studies are variously designed. The weakest are one-time cross-sectional studies where a population is sampled for exercise levels and health markers. Cohort studies repeatedly sample a group of people over time (also known as longitudinal studies) for variables to determine whether certain factors increase or decrease the health markers of interest. Statistical techniques are used to minimize the effects of confounding variables that may obscure the relationship between the independent and dependent variables. Meta-analysis studies present no new data. Instead, they survey the existing literature and perform statistical analysis across the comprehensive set. The gold standard for research is the randomized control trial (RCT), a type of intervention study. In an RCT, participants are assigned randomly to one of two or more groups. One of the groups is the baseline or control group, where there is no intervention or application of the independent variable. This variable is manipulated in the other groups to test for effects on the dependent variable. Another 

The study described below is the first intervention study to show that high-intensity exercise promotes better cognition in patients with mild cognitive impairment (MCI). Results show it protects the hippocampus regions vulnerable to Alzheimer's Disease (A.D.) for at least 12 months after training cessation. The presence of MCI increases the progression to full A.D. by a factor of between five and ten.

 The Study of Mental Activity and Resistance Training (SMART) randomized 100 MCI participants over age 55 into four groups:

  1. Combined high-intensity progressive resistance training (PRT) and computerized cognitive training (PRT+CCT),
  2. PRT and sham CCT,
  3. CCT and sham PRT,
  4. Sham PRT and sham CCT.

The PRT was aggressive. It consisted of three sets of eight repetitions performed continuously at 80% of peak capacity on pneumatic resistance machines. Workout frequency was two or three times a week. The movements performed were chest press, leg press, seated row, standing hip abduction, and knee extension. 

The sham exercise consisted of stretching and seated calisthenics performed at a level with no increase in heart rate increase, strength, or balance. These sham exercises play the role of placebo in RCTs.

The cognitive training was conducted under university supervision with COGPACK, a computer-based software package developed for neurorehabilitation. Sham CCT was delivered by having participants watch documentary videos on various topics and administering simple questionnaires about them. CCT and sham CCT were matched for duration, setting, and sensorimotor stimulation. 

Physical, neuropsychological, and MRI assessments were carried out at the beginning of the study, at six months (directly after training),  and at 18 (6 months after training ended).  

 Studies have shown that hippocampal and posterior cingulate (P.C.) atrophy can precede cognitive impairment by several years and correlate with the degree of cognitive dysfunction at MCI diagnosis. 

The results of the study follow:

  1. Resistance exercise leads to long-term cognitive benefits with better global cognitive and executive function at 18 months.
  2. Resistance training increases P.C. plasticity and thickness while training is maintained. It is not maintained when training is stopped.
  3. Resistance training slows or stops atrophy of areas of the hippocampus that show AD-related degeneration.
  4. Preservation of P.C. volume during training correlates with long-term hippocampal preservation.
  5. PRT increases long-term functional connectivity between the P.C. and hippocampus.
  6. Protecting the AD-vulnerable areas of the hippocampus predicts long-term cognition.

Ever since Eugene Sandow and the origins of the physical culture movement in the 19th Century, strength training has been touted not only as a means to look good but also to be healthy. This continued through Jack Lalanne in the second half of the 20th Century. However, early scientific investigations of the impact of exercise on health focused on aerobics and cardiovascular disease. Kenneth Cooper's work in the 1960s is an early example. Most recently, research has uncovered the importance of strength training, particularly progressive resistance training, in attenuating the onset and effects of osteoporosis, sarcopenia, depression, and, now, dementia. 

References:

  • Manly JJ, Jones RN, Langa KM, et al. Estimating the Prevalence of Dementia and Mild Cognitive Impairment in the U.S.: The 2016 Health and Retirement Study Harmonized Cognitive Assessment Protocol Project. JAMA Neurol. 2022;79(12):1242–1249. doi:10.1001/jamaneurol.2022.3543 
  • Kathryn M. Broadhouse, Maria Fiatarone Singh, Chao Suo, Nicola Gates, Wei Wen, Henry Brodaty, Nidhi Jain, Guy C. Wilson, Jacinda Meiklejohn, Nalin Singh, Bernhard T. Baune, Michael Baker, Nasim Foroughi, Yi Wang, Nicole Kochan, Kevin Ashton, Matt Brown, Zhixiu Li, Yorgi Mavros, Perminder S. Sachdev, Michael J. Valenzuela, Hippocampal plasticity underpins long-term cognitive gains from resistance exercise in MCI, NeuroImage: Clinical, Volume 25, 2020,102182, ISSN 2213-1582, https://doi.org/10.1016/j.nicl.2020.102182.