Physical activity has been demonstrated to benefit brain health. However, it was previously unknown whether the existing recommendations for duration and intensity of physical activity have any substantive benefits. The researchers in this study attempted to address this questions by comparing temporal lobe volumes among older adults who met the physical activity recommendations and those who did not meet the recommendations.
The individuals who met the current moderate and vigorous physical activity (MVPA) recommendations had larger temporal lobe volumes compared to those who did not meet the recommendations, and the effect was even greater for individuals with higher risk for Alzheimer’s disease (based on family history or ApoE genotype). The study highlights the importance of physical activity for individuals at risk for Alzheimer’s disease.
The study cohort included ninety-one older adults, ages 50–74 years, (mean age = 64 ± 5.8) from the Wisconsin Registry for Alzheimer’s Prevention (WRAP) who were cognitively healthy and volunteered to participate. The study cohort included a large proportion of participants at-risk for Alzheimer’s disease (78%), including individuals who possess either a parental family history of Alzheimer’s disease (70%), and/or the apolipoprotein epsilon 4 allele (APOE ε4) (46%). This percentile breakdown reflects the makeup of the more than 1500 cognitively healthy older adults who comprise the WRAP cohort. All participants were evaluated using the mini-mental state examination (MMSE ≥ 24) and deemed to be cognitively healthy (MMSE = 29.3 ± 1.1). Also, all participants did not have any major medical conditions (e.g. neurological diseases, psychiatric disorders), and were deemed safe for neuroimaging procedures.
Some of the previous research on physical activity and Alzheimer’s disease has included self-reported physical activity, which has inherent limitations. In order to obtain more accurate measures of physical activity, all 91 participants wore an accelerometer on their hip for seven consecutive days, and were instructed to wear the device during all waking hours, other than when showering, swimming, or bathing. Accelerometry inclusion criteria was at least 10 hours of valid wear time per day for a minimum of three weekdays and one weekend day, and accelerometer data were processed in 1-second epochs. In order to calculate the number of minutes the participants spent in different intensity categories of physical activity, estimated METs were determined for each bout interval and were then separated into physical activity categories accordingly: <1.5 METs = sedentary, 1.5–2.99 METs = light, 3–5.99 METs = moderate and >6 METs = vigorous. Participants were categorized as either having met the physical activity recommendations or not based on the US Department of Health and Human Services recommendations of 150 minutes of MPVA per week.
All study participants underwent T-1 anatomic magnetic resonance images (MRIs), and temporal lobe regions of interest included superior, middle, inferior, temporal pole, hippocampus, parahippocampal, and entorhinal. The researchers averaged the values from the right and left hemispheres and then expressed them as a percentage of intracranial volume to account for differences in overall head size.
Of the ninety-one cognitively healthy participants who completed the study, twenty-nine participants met the physical activity recommendation of 150 minutes of MPVA and sixty-two did not. The groups did not differ on any measured demographic characteristics. After controlling for the effects of gender and age, there were significant group effects for the inferior temporal lobe and the temporal pole. The individuals who met current MVPA recommendations (MVPAR) had larger inferior temporal and temporal pole volumes compared to those who did not meet the recommendations. No significant group differences were observed for the other regions of the brain that were scanned. When the sample was limited to only individuals at-risk for Alzheimer’s disease (n = 22 met MVPAR; n = 49 did not meet MVPAR), the observed effect size for the inferior temporal lobe was strengthened, which highlights the importance of meeting the MVPAR for individuals with familial and/or genetic risk for Alzheimer’s disease.
It is important to note that in this study, 32% of participants met the weekly physical activity recommendation which is higher than the reported national average of 5% of older adults. This larger than average percentage of individuals who met the MVPAR allowed for meaningful comparisons between the groups. However, this large percentage suggests that the volunteer cohort may not be reflective of the general US population of older adults. The researchers recommend future studies aimed at manipulating physical activity and determining whether a change in physical activity levels is necessary to preserve temporal lobe volume.
- Dougherty RJ, Ellingson LD, Schultz SA, et al. Meeting physical activity recommendations may be protective against temporal lobe atrophy in older adults at risk for Alzheimer’s disease. Alzheimers Dementia (Amst). 2016;4:14-7.