Doing high-intensity endurance exercise reduces morning cortisol levels in patients with Parkinson’s disease, which may have an impact on the progression of non-motor signs and symptoms, a pilot study suggests.

While other studies are needed to confirm if lowering cortisol with physical exercise works for delaying disease worsening, this data supports the further exploration of the role played by the hormone in non-motor symptoms of Parkinson’s.

The study, “ Endurance Exercise Reduces Cortisol in Parkinson’s Disease With Mild Cognitive Impairment, ” was published in the journal Movement Disorders.

Parkinson’s disease is a complex disorder associated with both motor and non-motor symptoms including sleep problems, depression, and cognitive impairment.

There is evidence that a malfunction of the hypothalamic-pituitary-adrenal axis (HPA) is involved in the progression of non-motor symptoms of Parkinson’s due to an overproduction of the hormone cortisol.

HPA is a system in the body crucial for stress management. It involves a set of complex interactions between two parts of the brain — the hypothalamus and the pituitary glands — and the adrenal glands located at the top of each kidney, which are regulated by different hormones.

After a stressful or threatening event, the HPA axis is activated and several “stress hormones,” primarily cortisol and adrenaline, are released by the adrenal glands into the bloodstream. As the blood levels of cortisol rise, they start to block the release of other hormones from the hypothalamus and the pituitary that, in turn, will induce a drop in cortisol levels.

This type of negative feedback loop is one mechanism by which HPA regulates itself to avoid excessive and sustained production of cortisol.

Beside this natural stress management process, cortisol is also important for a wide range of vital processes, including metabolism and the immune response. There has been a long-standing association between raised or impaired regulation of cortisol levels and a number of psychiatric conditions such as anxiety and depression, even though this is not yet fully understood.

Elevated morning cortisol levels have been reported in Parkinson’s patients. Accordingly, there is evidence that elevated cortisol in Parkinson’s patients is linked to symptoms such as depression and risk behavior.

Physical exercise is associated with a lower production of cortisol in healthy individuals, and there is evidence that it may also reduce the risk and rate of Parkinson’s progression.

Based on this data, the researchers reasoned that doing exercise could lower daytime production of cortisol in Parkinson’s patients, with possible implications for delaying the progression of their non-motor symptoms.

To test this theory, they conducted a small study in which they measured the levels of cortisol in saliva samples collected from eight Parkinson’s patients with mild cognitive impairment (ages 53 to 79). Over six months, participants were asked to perform high-intensity treadmill endurance exercise.

The exercise program included five to 10 minutes of warm-up, 30 minutes of exercise at 80-85% maximum heart rate, followed by five to 10 minutes of cool-down. Participants exercised an average of 2.5 days per week, and over the first eight weeks of training, exercise duration and intensity were gradually increased to target levels.

Saliva samples were collected before and after completing the program, and at specific times immediately after waking up (0, 0.25, 0.50, and 0.75 hours after awakening) and at periods throughout the day (three, six, nine, and 12 hours after awakening).

Overall, cortisol secretion of Parkinson’s patients more closely resembled that of healthy people after they had completed the training program.

Results showed there was an average 19% reduction in cortisol secretion, compared with the pre-training period. In addition, while cortisol reduction was significant during the times immediately after waking up, it was not in the periods later in the day.

“These data support the need for further exploration of HPA axis dysregulation in Parkinson’s disease,” the researchers wrote. “To understand not only its potential role in the mechanisms underlying non-motor symptoms of Parkinson’s, but also its responsiveness to intervention studies such as physical exercise that can improve non-motor symptoms.”