An awful lot of health studies track a small group of people—say a hundred or so—over a short period of time—say, from a few weeks to a year. Those studies can be useful, but if you want really powerful data, what you need is a large cohort to study for decades. Incidentally, Cardiff University has an impressively large group. Their Caerphilly Cohort Study tracked, published in PLOS One, includes a staggering 2,235 men aged thirty-five to sixty-nine tracked over the course of thirty-five years, with the aim to examine the relationship between healthy behaviours, chronic disease, and cognitive decline.
What they found is fairly simple in theory, but not often put into practice. If a man followed four of five healthy behaviours—maintain a low body weight, keep alcohol intake low, don’t smoke, exercise regularly, and keep a healthy diet—he could expect a sixty per cent decline in dementia and other cognitive impairments compared to other men his age, along with seventy per cent less chance of diabetes, heart disease, and stroke.
So, pick a vice, but remember: you only get one.