Exercise and the brain

Researchers at the University of California at San Diego (UCSD) surveyed more than 300 HIV-positive people about their overall health, behaviours and activity, including exercise habits. Additionally, participants underwent complex assessments of their brain health. The researchers found that participants who reported that they exercised had about 50% less neurocognitive impairment than participants who reported not exercising. Future clinical trials with supervised exercise are needed to help doctors determine the amount of exercise needed to prevent or reverse the decline of the brain among HIV-positive people.

Study details

Researchers recruited 335 HIV-positive adults for this study.

The average profile of participants was as follows:

  • age – between 20 and 79 years
  • gender – 76% men, 24% women
  • education – up to one year of college
  • taking ART – 82%
  • received a diagnosis of AIDS in the past – 65%
  • duration of HIV infection – from one month to 28 years

In their survey, researchers stated that exercise was “any activity in which the heart beats rapidly” and gave participants the following examples:

  • running
  • jogging
  • lifting heavy weights
  • aerobics
  • hockey
  • football
  • soccer
  • squash
  • basketball
  • cross-country skiing
  • judo (and similar sports)
  • roller-blading/skating
  • vigorous swimming
  • vigorous long-distance cycling

Participants also underwent neurocognitive assessments.

Researchers assessed participants’ health and their use of substances and checked for the presence of mood disorders. In some cases, researchers also accessed medical records to check lab test results and for the presence of other conditions.

People who had issues unrelated to HIV that could affect neurocognitive assessments were not included in this study. According to the researchers, such issues included the following:

  • seizures
  • head trauma
  • learning disabilities
  • psychotic disorders
  • current substance use


According to researchers, participants who reported engaging in exercise had the following:

“Significantly more formal education, [were less likely to have been diagnosed with AIDS], higher current CD4+ counts, [were less likely to be depressed] and [had better overall physical health].”

Results—Cognitive impairment

Overall, more participants who did not exercise in the past three days were significantly likely to have neurocognitive impairment (31%) compared to people who did exercise (16%).

Further comparisons

It seems obvious that some of the study’s findings could have been affected by factors that were not measured or that were not adjusted for in the researchers’ comparisons and calculations. For instance, it is possible that people who have more years of education could be expected to exercise more regularly and this could have inadvertently biased researchers’ interpretations of their findings.

To try to overcome such potential biases (or confounding factors), the researchers created complex algorithms that took into account some of these issues. Also, they analysed a sub-group of participants: 83 people who exercised and 83 people who did not. In this sub-group of 166 people, participants had similar levels of education, gender, ethnicity and age. The analysis of this subgroup confirmed that participants who reported no exercise had the following:

  • lower CD4+ cell counts
  • higher rates of depression at the time of the survey
  • greater risk for AIDS in the past

Furthermore, in the subgroup analysis, a lack of exercise remained a significant predictor for reduced neurocognitive functioning even when researchers took into account several potential confounding factors.

Bear in mind

The UCSD study is cross-sectional in design, which means it is akin to a snapshot in time. Such studies are good at finding associations but can never prove cause and effect. That is, such studies cannot prove that not engaging in regular vigorous exercise will lead to a greater risk of neurocognitive decline. Such conclusions can only be drawn from well-designed and expensive prospective studies that monitor participants over time and compare different interventions (exercise vs. no exercise).

However, the present study’s findings do support clinical trials of exercise to assess its impact on brain health among HIV-positive people.

—Sean R. Hosein


  1. Trøseid M, Ditlevsen S, Hvid T, et al. Reduced trunk fat and triglycerides after strength training are associated with reduced LPS levels in HIV-infected individuals. Journal of Acquired Immune Deficiency Syndrome. 2014 Jun 1;66(2):e52-4.
  2. Fazeli PL, Woods SP, Heaton RK, et al. An active lifestyle is associated with better neurocognitive functioning in adults living with HIV infection. Journal of Neurovirology. 2014 Jun;20(3):233-42.
  3. Mapstone M, Hilton TN, Yang H, et al. Poor aerobic fitness may contribute to cognitive decline in HIV-infected older adults. Aging and Disease. 2013 Aug 27;4(6):311-9.
  4. Dufour CA, Marquine MJ, Fazeli PL, et al. Physical exercise is associated with less neurocognitive impairment among HIV-infected adults. Journal of Neurovirology. 2013 Oct;19(5):410-7.