In the early 1990s, the researchers asked older people living near Rotterdam, the Netherlands, to participate in a follow-up study. They interviewed and examined people who agreed to participate and followed them for 8 to 9 years. During this time, the researchers routinely communicated with doctors and reviewed medical records to see which persons had hip fractures. The researchers also looked at computerized pharmacy records to see which persons were given thiazide diuretics. They counted the days that the diuretics were prescribed and noted when diuretics were stopped. The researchers then compared numbers of hip fractures among the people given and not given diuretics.