Men are more likely to suffer more from sleep-disordered breathing than women as a result of stress in early life, according to new research.
The Canadian study found that stress experienced as a baby, such as separation from the mother, can disrupt the development of male babies’ hormone regulation systems leading to respiratory problems in adulthood.
Dr Richard Kinkead, who led the study at the Centre de Recherche du CHU de Québec, Canada, said: “Over the past decade, our laboratory has established that neonatal stress has persistent and sex-specific effects on blood pressure and respiration, with consequences that persist well into adulthood.”
In this study, on male rats, those removed from their mothers in early life had a greater hypoxic ventilatory response (HVR) – breathing difficulties when in reduced oxygen atmosphere, as at high altitude or when the respiratory system relaxes during sleep – than those in a control group left undisturbed with their mothers.
"We use rats because much like pre-term infants their brains are immature at birth and highly sensitive to stress," added Dr Kinkead. “Moreover, there are similarities between their cardio-respiratory system and ours, so this study provides real insights into the conditions that cause respiratory disorders in the human population.”
However, surgical ablation of the testes to reduce the testosterone in the body proved to significantly reduce HVR.
Researchers found an increased number of androgen receptors in the brainstem of the stressed rats, which is the likely reason why these rats were more sensitive to the presence and withdrawal of testosterone.
Dr Kinkead concluded: "The different results in males and females in our previous studies suggested that sex hormones were contributing to the emergence of respiratory issues.
"Stress in early life did not affect long-term, baseline hormone levels. But when oxygen levels were lowered, there was a significant increase in the levels of testosterone circulating in the blood of stressed rats, but not in the controls. Though not well understood, this abnormal regulation of testosterone release seems to contribute to the respiratory problems we observed."
Sleep-disordered breathing is a significant problem and is commonly associated with other pathologies such as hypertension and depression. The researchers hope their findings will advance understanding of the processes around the condition and potential treatments.
Research paper: Fournier S, Gulemetova R, Joseph V and Kinkead R. (2014) Testosterone potentiates the hypoxic ventilatory response of adult male rats subjected to neonatal stress. http://ep.physoc.org