It's much earlier than you think: the effects of a poor lifestyle are felt from this age.

Do you drink alcohol, smoke, and don't exercise much, thinking it won't have an impact for decades? Bad news: these bad habits affect your health faster than you might think.
Finnish researchers analyzed the physical and mental health of hundreds of people born in Finland, from early adulthood to their 60s. Various physical health indicators were observed: blood pressure, waist circumference, cholesterol, blood sugar levels, etc. On a psychological level, symptoms of depression and well-being questionnaires were conducted.
Participants were asked to report their alcohol consumption, tobacco use, and physical activity. Researchers observed that people who had one or more of these bad habits had poorer health scores—both physical and mental—as early as age 36. Specifically, people who exercised little had poorer physical health, those who smoked had poorer mental health, and heavy alcohol consumption was associated with poorer physical and mental health.

Overall—and logically—the more numerous and long-term the bad habits, the greater the impact, particularly on physical health. The results of this study "underscore the importance of addressing risky behaviors, such as smoking, excessive alcohol consumption, and physical inactivity, as early as possible to prevent the damage they cause from accumulating over the years and leading to poor mental and physical health later in life," the study 's lead author said in a statement.
Alcohol, tobacco, and lack of physical activity are the main risk factors for preventable chronic diseases—such as cancer and heart disease—which "cause nearly three-quarters of deaths worldwide," the study's lead author points out. They can impact both physical and mental health well before the age of 36, hence the importance of adopting healthy habits as early in life as possible.
L'Internaute