Why where you live might be affecting your antibiotic prescriptions – and why that matters

By Catia Nicodemo, Mayar Al Mohajer, David Slusky, David Nix

Imagine going to your GP and being prescribed antibiotics, not because of your illness alone, but partly because of where you live. It might sound surprising, but that’s exactly what our research set out to investigate. 

Titled 'Investigating socioeconomic deprivation and antibiotic prescribing among older medicare patients using an instrumental variable approach' and published in Antimicrobial Stewardship & Healthcare Epidemiology, our study looked at whether socioeconomic deprivation – that is, how disadvantaged a person’s local area is – influences how likely older patients on Medicare in the US are to receive antibiotics. And for the first time, we used a special statistical method to help move beyond simple associations and uncover a possible causal link. 

We know that older Americans in poorer areas are often prescribed more antibiotics, but until now, it wasn’t clear if deprivation was actually causing this, or if other hidden factors were at play – like limited access to healthcare, or different prescribing behaviours across regions. 

There’s a well-known pattern in healthcare: where you live often affects how healthy you are. But does it also affect how doctors prescribe? 

To dig deeper, we used a clever approach called an instrumental variable (IV) model, which helps separate out cause from coincidence. In this case, we used the maximum Earned Income Tax Credit (EITC) – a US policy measure that reflects broader economic conditions in each state – as our tool to isolate the effects of deprivation on prescribing. 

We analysed data from over 161,000 Medicare Part D providers (private insurance companies approved by Medicare to offer prescription drug coverage plans), looking at antibiotic prescriptions given to older patients over a ten-year period (2013–2022). We then matched this with a Social Deprivation Index (SDI) – a composite score based on things like poverty, unemployment, housing conditions, and education levels in each area. 

Here’s what we found: 

• Higher deprivation led to more antibiotic days supplied per 100 beneficiaries, even after accounting for other factors like provider experience, patient age, and location. 

• Two specific components of deprivation – unemployment and the prevalence of single-parent families – were especially associated with higher prescribing. 

• Interestingly, areas with crowded housing saw lower antibiotic use, which might suggest barriers to accessing care. 

• Providers caring for a higher proportion of Black and Hispanic patients tended to prescribe fewer antibiotics overall. 

This study suggests that socioeconomic deprivation doesn’t just influence health outcomes – it also affects the way care is delivered. The more deprived an area is, the more likely patients are to receive antibiotics, regardless of whether they truly need them. 

This has serious implications. Not only does overprescribing fuel antibiotic resistance, a growing public health threat, but it also puts vulnerable patients, particularly those aged 65 and over, at greater risk of side effects, dangerous infections like Clostridioides difficile, and unnecessary healthcare costs. 

It also raises difficult questions about equity: Are some communities being overtreated, while others are undertreated because of where they live? Is prescribing filling the gap where other health services are lacking? 

Our findings could help shape future targeted public health interventions. By identifying which communities are most affected, policymakers and healthcare providers can focus on improving education, access, and prescribing practices in those areas. 

But we also need more research. We couldn’t examine whether the prescriptions were clinically appropriate – that’s the next step. And we know that patterns may have shifted during the COVID-19 pandemic, especially in deprived areas. 

This study is a step forward in understanding how the social determinants of health intersect with clinical decisions – even ones as seemingly routine as an antibiotic prescription. 

It shows us that prescribing is not just a matter of science, but also one of social context. Tackling antibiotic overuse will require more than clinical guidelines – it will require addressing the broader inequalities that shape the health of our communities. 

Reference: 
Al Mohajer M, Slusky D, Nix D, Nicodemo C. Investigating socioeconomic deprivation and antibiotic prescribing among older Medicare patients using an instrumental variable approach. Antimicrobial Stewardship & Healthcare Epidemiology. 2025;5:e110. doi: 10.1017/ash.2025.185