Mark O'Connor, MD: Endocrinologist and Clinical Researcher

• Endocrinologist, UMass Memorial Health
• Assistant Professor of Medicine, UMass Chan Medical School

Dr. O’Connor earned his medical degree at UMass Chan Medical School before completing residency at Dartmouth-Hitchcock Medical Center.  He returned to Worcester to work as a hospitalist at Memorial Hospital before pursuing fellowship training at Massachusetts General Hospital, where in addition to treating patients with a wide range of endocrine disorders, he studied the genetics of type 2 diabetes at the Broad Institute of MIT and Harvard.  

"In a sense, he returned home," said Dr. Samir Malkani, Clinical Chief of the UMass Memorial Diabetes Center of Excellence.  When Dr. O’Connor was a medical student, Dr. Malkani was his first endocrinology supervisor. "I feel very fortunate that he decided to begin his diabetes and endocrinology care and research career here."

What Attracted Dr. O’Connor to Worcester's Diabetes Center of Excellence       

“I like the multidisciplinary approach of the DCOE,” he said.  He appreciates having specialists like a nephrologist with an interest in diabetic kidney disease on the care team, since diabetes is the most common cause of kidney disease. “I also value our diabetes educators who help with everything from insulin pumps to nutrition and so many other topics affecting people with both type 1 and type 2.” 

He highlighted the clinic's workflow and spoke specifically about the value of point-of-care A1c testing. “It optimizes patient care. Our patient care assistants administer the A1c test, and results are ready when the doctor enters the exam room,” he said.  “If people use CGM or an insulin pump, that data is downloaded for us ahead of time so we can maximize our time formulating a plan with the patient.”  

“Specialty Pharmacy is also a great resource,” added Dr. O’Connor. “Our care team works hard to find the most cost-effective medication for each patient and helps people navigate the challenges of the health insurance system.”

Why Diabetes Care

Dr. O’Connor chose to focus on diabetes care because of the high prevalence of type 2 diabetes (T2D).

“I felt that specializing in diabetes was an opportunity to improve the lives of a large number of people. Endocrinology allows me to build long-term relationships with patients while participating in research that has the potential to improve diabetes care for future generations.” 

He helps people develop individualized care plans that incorporate the latest treatment options using a team-based approach in which an endocrinologist, nurse practitioner, and diabetes educator work together with each patient.

Challenges of Treating Diabetes

Dr. O’Connor understands that healthcare costs such as medication prices as well as insurance co-pays and deductibles make it difficult for people with type 1 and type 2 diabetes. Similarly, the costs of obtaining and preparing healthy foods and getting regular exercise can be significant, especially for people working and raising families.  And for type 1 diabetes, especially, he recognizes the psychological toll it takes to manage a disease that requires such constant attention. “Our ability to pay attention to multiple things at the same time is limited,” said Dr. O’Connor. “When diabetes is a constant focus it can affect your mental well-being.”

Diabetes Research

Dr. O'Connor is passionate about research because diabetes affects millions of people, yet many important questions remain unanswered. His research interests include diabetes genetics, diabetes technology, and clinical trials that evaluate new approaches to improving outcomes for people living with diabetes.

His research has included studies examining the genetics of type 2 diabetes and identifying genetic variants associated with diabetes risk in African American populations. More recently, his work has expanded to studies evaluating continuous glucose monitoring and medications that may reduce the risk of diabetes-related complications.

Clinical Studies

Dr. O'Connor is leading recruitment for the PRECIDENTD study, a multi-site clinical trial comparing two commonly prescribed medication classes for type 2 diabetes—GLP-1 receptor agonists and SGLT2 inhibitors. The study aims to better understand which medications provide the greatest protection against cardiovascular and kidney disease, helping answer an important clinical question faced by patients and healthcare providers every day. To learn more or determine your eligibility, email Dr. O’Connor at precidentd@umassmed.edu

He was principal investigator for the GOOD-ER Study, which evaluated the use of continuous glucose monitoring in adults with type 2 diabetes treated in the emergency department. The study was designed to determine whether CGM technology can improve diabetes management and help reduce future emergency department visits.

Through both investigator-initiated and multi-center clinical trials, Dr. O'Connor is committed to bringing new treatment options and research opportunities to patients while advancing the future of diabetes care.
 

Type 2 diabetes (T2D) affects nearly 1 out of 12 adults worldwide, but genetic risk factors are still not fully understood.

Over the past decade, genome-wide association studies (GWAS) have identified hundreds of genetic regions associated with T2D risk. Dr. O'Connor's research explored a different analytical approach that revealed previously undetected genetic variants, improving scientists' understanding of the disease. 

Dr. O'Connor led the largest GWAS meta-analysis study ever done using a recessive model for T2D. The results of “Recessive Genome-Wide Meta-analysis Illuminates Genetic Architecture of Type 2 Diabetes” published in Diabetes demonstrate that recessive models can identify new genetic risk factors for T2D, including variants with large effect sizes.

Dr. O’Connor’s Favorites

Hobbies/Activities: Hiking, running, and playing the piano.

Massachusetts Locations: Lake Park, Purgatory Chasm, Moore State Park

TV Shows: Scrubs

Music: Traditional, Classical, Jazz