Using Personal Data: Consumer Perspectives and Protection Laws 

Dr Flanagan and his colleagues have conducted several studies — involving in-person focus groups and phone interviews — to explore how consumers feel about sharing data from their loyalty cards for health research. 

In one study, 54% of consumers said they would be willing to share these data for research.3 Consumers were more likely to donate their data if they understood the purpose of donation, but “social duty” was the strongest predictor of whether consumers would donate their data. 

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“People are altruistic,” Dr Goulding said. “They have a social duty and want to help in this area.” 

The research also highlighted several areas that consumers are concerned about, especially about how the data would be managed, whether the data could be used for purposes other than the study without their knowledge, and whether the data would be anonymized to protect the consumers’ identity and location.4,5

Some of these safeguards may be harder to ensure in the United States than in the UK and Europe, which have data protection laws that give consumers ownership of their personal data and agency over how the data are used.6 

“[In the US], right now, what we have is a patchwork of state and sectoral laws that, in many cases, do a very poor job of limiting how a [retail store] can use the information that it collects through a loyalty program and what it has to disclose upfront,” said John Davisson, senior counsel and director of litigation for EPIC, a nonprofit research and advocacy group.

He noted, however, that retail stores are different from studies. Studies are generally subject to institutional review boards that provide strict oversight to ensure data are managed securely. For example, even if a grocery store were at liberty to hand over loyalty card data to a third-party such as a research group, the researchers would probably be obligated to obtain consent from the consumers.  

All the concerns around data privacy were set off about a decade ago because of the Target retail chain, Dr Grande said. An investigation revealed that the stores tracked purchases made by expectant parents and mailed them targeted — sometimes privacy-violating — advertisements.7 

“For the companies that want to use consumer data for marketing, there are no barriers or rules, and particularly in the US, it is the Wild West,” Dr Grande said. However, he added, researchers who study consumer data generally have to follow strict rules about how they collect, aggregate, and use those data.

Next Steps: More Research and Real-World Applications

Researchers are far from having enough evidence on the link between shopping data and cancer risk to implement any kind of warning system through loyalty card programs, Dr Grande said. 

“The study was a proof of concept about whether this personal information is useful or not, and, if we determine that it is, it is an entirely different question about how we can build it into systems that can act on the information. I have not seen any examples of anyone figuring out how to do that yet,” he added.

If Dr Flanagan and his colleagues can validate the results of their first study, they hope to conduct studies of the most acceptable ways to alert consumers. Through discussions with patients and primary care doctors, the researchers have identified some ways in which this could work. For example, loyalty card systems could send a letter to consumers or their doctor about a potential risk detected by an algorithm, or even automatically make an appointment for the consumer at a diagnostic clinic, Dr Flanagan said. 

If shopping data could be used by an algorithm to detect cancer risk in a real-world setting, it would be important to consider how a loyalty card system could miss important populations, Dolan noted. 

“One bias in shopping data is older women are more likely to have loyalty cards, but they are underrepresented in many other data sets,” such as those derived from social media platforms, Dolan added.   

Compared with using shopping data in a research setting, their use in a real-world, health notification system “would add another complexity,” Davisson said. He added that it would be important to have all the same safeguards, such as restrictions on who could access the data and how they could use it. 

“If consumers are interested in it, I don’t think it is out of bounds, but you have to be very careful to make clear to them how their information is being used and communicate the conclusions of the algorithm you are using,” Davisson said.  

Disclosures: All interviewees reported having no relevant disclosures.


1. Brewer HR, Hirst Y, Chadeau-Hyam M, et al. Association between purchase of over-the-counter medications and ovarian cancer diagnosis in the Cancer Loyalty Card Study (CLOCS): Observational case-control study. JMIR Public Health Surveill. Published online January 26, 2023. doi:10.2196/41762

2. UK National Health Service. Bloating. Updated March 3, 2022. Accessed April 20, 2023. 

3. Skatova A and Goulding J. Psychology of personal data donation. PLoS One. 2019;14(11):e0224240. doi:10.1371/journal.pone.0224240

4. Flanagan JM, Skrobanski H, Shi X, Hirst Y. Self-care behaviors of ovarian cancer patients before their diagnosis: Proof-of-concept study. JMIR Cancer. 2019;5(1):e10447. doi:10.2196/10447

5. Dolan EH, Shiells K, Goulding J, Skatova A. Public attitudes towards sharing loyalty card data for academic health research: A qualitative study. BMC Med Ethics. 2022;23(1):58. doi:10.1186/s12910-022-00795-8

6. Information Commissioner’s Office. About the DPA 2018. Guide to Data Protection. Accessed April 20, 2023. 

7. Duhigg C. How companies learn your secrets. New York Times Magazine. Published February 16, 2012. Accessed April 20, 2023.