[cameldrv]

Location data is very readily available, so you can easily correlate visits to a health facility with a treatment, and even with an offset, you can probably uniquely identify someone with 4 visits depending on the size of the medical facility.

[evandijk70]

I had access to several health datasets for my research in the past. Date of birth was rarely given, especially for the bigger projects where there were more resources to allocate to privacy protection. Neither was date of death, location, or visits to a health facility with a treatment. Typically the relevant variables are age (in years), treatment type and possibly number of cycles. Probably insufficient to identify someone without access to hospital records. But if you have that, you have all these data anyways.

Most researchers likely would want to summarize these data in a similar way anyway, so this works out nicely.