Biological aging refers to how the body changes over time, whereas chronological aging is defined by the actual age of the body. For example, in two people who are both 70 years old, one may be showing more signs of aging than the other. Biological age can be affected by lifestyle factors such as diet and exercise, environmental factors such as socioeconomic status or biological factors including genetics or chronic illness. A study published last April in Nature found that the shingles vaccine reduced the probability of a new dementia diagnosis by approximately 20% over a follow-up period of seven years. “The results support the hypothesis that shingles vaccination may influence key biological systems relevant to aging, though effects appear domain-specific and vary over time,” Kim and Crimmins write in the study.