A medical study might be envisioned, executed and published during one PhD candidate’s advanced degree study course. But that’s not the best way to actually learn new things related to science and medicine, according to The Atlantic.

That’s because gathering accurate and nuanced information about one person, or even a population of people, takes time. A longitudinal study executed over a lifetime might be able to tell more about how a seemingly healthy person goes on to develop certain conditions than a once-off look at a group.

Measuring any given metric during a certain point in time might not be as useful as measuring it over an even slightly extended period. For example, people’s blood pressures and heart rates change throughout the day—knowing an individual’s fluctuations might help better predict potential problems for them specifically and also give a more complete picture of a population-based measurement.

Check out The Atlantic for examples of long-term studies, observations and investigations that might do a better job of teasing out the real relationships between health markers than short-term views, including one Harvard study that has lasted 75 years.