People working in shift-based jobs and those who easily get exhausted, may be at a high risk of developing Alzheimer's disease later, says a study.

It could be because shift work often disrupts the circadian rhythm, which can lead to sleep disorders and daytime fatigue. This disruption causes the brain to deteriorate resulting in memory disorder or Alzheimer's disease. In the study, published in the journal Sleep, scientists showed that a variation in the receptor 1A (MTNR1A) gene combined with a lifestyle that disrupts the circadian rhythm -- caused by shift job -- can increase the risk of Alzheimer's disease.

However, "the finding of a common risk gene for both job-related exhaustion in shift workers and Alzheimer's disease doesn't directly mean that shift work would predispose to Alzheimer's disease," said Sonja Sulkava from the University of Helsinki in Finland. "But the combination of genetic predisposition and a lifestyle that disrupts the circadian rhythm can increase the risk of Alzheimer's disease," Sulkava said.

The link between a weaker signalling of endogenous melatonin and Alzheimer's disease supports the view that regulation of the circadian rhythm plays a role in the development of Alzheimer's disease. "Another possible interpretation is that the brain dysfunctions related to Alzheimer's disease impair the tolerance to shift work decades before the onset of the clinical disease," Sulkava said.

The results showed that the link was only found in elderly but not in the younger patients. "Even though our results demonstrate a new molecule-level connection between the tolerance to shift work and incipient Alzheimer's disease, the now discovered genetic variation has a minimal effect on the individual level and it can't be used to risk assessment or prediction," noted Tiina Paunio from the varsity.