What Happens to Your Data in Large Health Surveys

Every year, over 1 billion medical encounters globally generate 2.3 zettabytes of health data—enough to fill 4.6 billion laptops. From a blood pressure check at your GP to a lab test ordered for cholesterol, every piece of your health data joins this vast pool.

But what happens to it once collected in large health surveys?

In short: your data is collected, securely stored, pseudonymised or anonymised, and then analysed to improve treatments, predict disease trends, and plan healthcare resources—while laws like the UK GDPR and NHS guidelines protect your privacy.

However, risks such as potential re-identification, misuse, or inadequate consent persist if safeguards fail.

Why It Is Collected

Health data covers any information about your physical or mental health, past, present, or predicted future, including:

Why is it collected? Large health datasets are not only critical for research.

• Direct care: Managing your diagnosis, treatment, and appointments.
• Research and planning (secondary use): Tracking disease prevalence, evaluating treatment outcomes, planning hospital resources, and addressing health inequalities.

In the NHS, every patient has a unique NHS number, ensuring your data links correctly to your care while maintaining accuracy across providers.

Your Data Journey in Health Surveys

Collection: How Your Health Data Enters the System

Each year, the NHS records over 300 million patient interactions, generating petabytes (1 PB = 1,000,000 GB) of health data, according to The Guardian. Health surveys, whether for hypertension monitoring or COVID-19 symptom tracking, contribute significantly to this data volume.

For example:

These data points are entered into Electronic Health Records (EHRs), which the NHS estimates cover over 99% of the UK population. From there, your data becomes part of population-level health datasets used for research and healthcare planning.

Storage: Securing Massive Volumes of Health Data

After collection, the data is stored digitally in:

• Regional Data Lakes: NHS England alone manages over 60 regional health data repositories.
• Secure Data Environments (SDEs): Designed to hold sensitive data without allowing it to leave the environment.

The estimated total volume of health data globally was 2.314 zettabytes in 2020, equal to the storage of 4.6 billion typical laptops. In the UK, NHS Digital reported managing tens of petabytes of patient data annually.

Security measures include:

De-Identification: Making Data Safer for Research Use

Deidentifying Medical Documents with Local, Privacy-Preserving Large Language Models: The LLM-Anonymizer | NEJM AI https://t.co/B3JoaAXl99

— John Nosta (@JohnNosta) April 2, 2025

Before your data is analysed:

Anonymisation

• All personal identifiers (name, address, NHS number) are removed.
• The NHS has achieved complete anonymisation for over 85% of secondary-use datasets, reducing re-identification risk.

Pseudonymisation

• Replaces identifiers with coded strings (e.g., 10XX9PQ785), maintaining linkage across datasets while hiding identities.
• Enables advanced research while preserving privacy.

For example, your record in a hypertension dataset may appear as:

These processes follow ICO guidelines and GDPR compliance, ensuring the NHS can legally and ethically use your data for healthcare improvement.

Analysis: Turning Data Into Actionable Insights

Once de-identified, your data is pooled with millions of others:

• A hypertension dataset may contain data from over 1.5 million patients across England.
• Machine learning tools process these datasets, identifying patterns across variables like age, medication adherence, socioeconomic status, and comorbidities.

Benefits of Large Health Datasets

Potential Harms and Risks: The Numbers Behind Concerns

Using health data in large surveys and datasets is central to advancing medical research and healthcare planning, but this powerful tool comes with measurable risks that require careful management.

In 2023 alone, the UK reported 156 confirmed health data breaches, prompting regulatory investigations and potential enforcement actions against organisations involved. These breaches, while representing a small fraction of overall data use, highlight the real threat of data loss or unauthorised access in an environment where patient trust is critical.

Discrimination and stigma risks are also present, particularly if data relating to ethnic background, income levels, or geographic location is mishandled. Such misuse could lead to unfair targeting of specific groups or reinforce existing healthcare disparities if not properly governed.

Disempowerment remains a pressing concern, with 42% of UK patients reporting they feel uninformed about how their health data is used for secondary purposes such as research or planning. This indicates a significant gap in transparency and communication, which can erode public trust in health systems if not addressed proactively.

Exploitation concerns have also surfaced as NHS data is sometimes shared with private technology and pharmaceutical companies for research under strict contracts.

While these partnerships can drive innovations, there is an ongoing debate on whether the NHS and patients receive fair value in return, particularly when private entities may develop profitable products using insights derived from public health data.

To address these concerns, the UK Information Commissioner’s Office (ICO) retains the authority to issue fines of up to £17 million for severe breaches of data protection within the health sector.

This regulatory power, combined with heightened public awareness, is placing health data handling under increasing scrutiny, ensuring that organisations must remain vigilant in their data stewardship practices.

How Is Your Privacy Protected? Applying the ‘Five Safes’ in Practice

To protect patient data in large health surveys, the NHS and all certified data controllers apply the ‘Five Safes Framework,’ ensuring that data use is lawful, ethical, and secure at every stage:

The Five Safes Framework

Additional Protective Layers

Beyond the Five Safes, protections for patient data include:

• Technical Security: The NHS uses AES-256 encryption to protect data during storage and transfer. Systems are layered with secure access protocols, intrusion detection, and physical security measures across data centres.
• Legal Protections: Data controllers are bound by the UK General Data Protection Regulation (GDPR) and the Data Protection Act 2018, which require stringent compliance, clear accountability, and transparency about how patient data is handled.
• Patient Rights: Patients maintain the right to opt out of secondary use of their data. In 2024, over 1.2 million UK patients exercised this right, reflecting an increasing demand for autonomy in data usage without affecting the direct care they receive.

Who Can Access Your Health Data?

@dr_arthur_ Do healthcare professionals have access to your healthcare records? Well no, not all the time. GPs rarely have access to hospital notes and vice versa. Some systems do allow shared records, but they’re often very poorly organised and incomplete. I strongly believe the lack of digitalisation is one of the things holding the NHS back, and needs to be a serious focus of NHS reform! #doctor #hospital #medicine #nhs ♬ original sound – Dr_Arthur_

Access to patient data in large health datasets is highly regulated, ensuring it is only used where it benefits patient care, research, or public health planning.

 Permitted Access

• NHS Bodies: Including GPs, hospitals, regional health authorities, and planning groups, using data for direct patient care, system management, and resource planning.
• Academic Researchers: Universities and authorised research bodies can access anonymised or pseudonymised datasets to conduct public health research, treatment effectiveness studies, and epidemiological modelling.
• Charities and Non-Profits: Health charities may use data for studies that improve patient care and identify emerging health trends within specific communities.
• Pharmaceutical and Technology Companies: Access is granted under strict contracts for drug safety monitoring and the development of new treatments, with oversight to ensure patient benefits and data protection compliance.

Prohibited Access

• Marketing Use: Entities intending to use health data for direct marketing without explicit, informed patient consent are barred.
• Unlawful Purposes: Organisations or individuals lacking a lawful, ethical, and beneficial purpose for data use cannot access NHS health data.
• Insecure Systems: Any user or organisation failing to meet security, governance, or compliance standards will be denied access.

How Is Data Stored Securely?

Advanced Infrastructure and Compliance

The NHS and its partner organisations operate advanced infrastructure to ensure the security and integrity of health data, particularly when used in large-scale surveys and secondary research.

• Secure Data Environments (SDEs): These environments ensure that sensitive data remains within secure, encrypted servers. Data does not leave the environment; instead, authorised users access and analyse it remotely, ensuring tight control over who interacts with patient data.
• Layered Encryption: Encryption protocols protect data during both transfer and storage phases, ensuring that even if data is intercepted, it remains unreadable without authorised decryption keys.
• Access Monitoring: Every access attempt is logged, recording who accessed the data, when, and for what purpose, providing a robust audit trail and accountability in case of irregularities.
• Regular Audits: NHS Digital and the ICO conduct audits to verify compliance with data protection and privacy regulations, ensuring all organisations managing patient data adhere to the required standards.

Communicating the results of these audits, research findings, and patient information transparently is also vital for public trust.

To present data visually in reports, policy briefs, and patient materials, many NHS teams and healthcare researchers use platforms like Depositphotos for sourcing high-quality, royalty-free medical illustrations and infographics, supporting clear and accessible communication without copyright concerns.

Example Scale of Security Measures

In 2024, the NHS processed over 1.3 billion secure system logins across its services, underscoring the immense scale of the infrastructure required to manage health data securely while ensuring real-time access for clinicians and researchers when needed.

Methodology: How We Crafted This Article

We reviewed current NHS, ICO, and GDPR guidelines on patient data use to ensure accuracy. We integrated 2023–2024 UK data breach and dataset statistics to reflect the real scale and stakes of health data handling. We included practical examples like hypertension surveys and machine learning studies to ground the topic in everyday relevance.

We structured the article using clear headings and tables to make dense information easier to digest. We placed the Depositphotos anchor naturally in context, showing its relevance in data communication without disrupting the educational flow. We kept the tone human, transparent, and direct to empower readers to understand what happens to their data.

Conclusion

Your health data is powerful. When collected and handled properly, it helps researchers improve treatments, predict future health trends, and plan resources that serve entire communities more effectively.

While there are real concerns about privacy and misuse, strong safeguards and patient rights exist to protect your data and give you a say in how it’s used.

Large health surveys are not just about data points—they’re about improving the quality of care for people like you and ensuring healthcare systems respond to real needs.

By understanding where your data goes, you gain confidence in how it helps shape the future of healthcare while protecting your privacy. In the end, your data, handled responsibly, is a tool for better health for you and everyone.