Suddenly feeling old may not be our imagination. A recent study published in Nature Aging examined the molecular changes of 108 adults between the ages of 25 and 75. The participants were tracked for a median of 1.7 years, with a maximum of 6.8 years, during which biological samples were collected and evaluated every three to six months from a range of sources, including the blood, stool, skin, mouth and nasal passages.

The researchers compared the samples obtained from participants at different ages and observed that people seemed to age more rapidly at age 44 and again at age 60. The changes at age 44 were mostly related to fat and alcohol metabolism, as well as an elevated risk of cardiovascular disease. The changes at age 60 related mostly to immune dysfunction and carbohydrate metabolism. According to Stanford Medicine Professor Michael Snyder, these findings might explain why people seem to have more trouble processing alcohol starting in their 40s and become more prone to illness in their 60s.