The hidden consequences of diabetes
One of the first times I entered the hospital as a medical student was to practice taking a history from a Black man living in the Bronx who worked on foot as a UPS delivery man. He told my classmates and I about his days running track and field, highlighting the incredible athletic feats that shaped his youth.
He had just undergone his second below-the-knee amputation.
He was in his forties.
And he had no clue how his ‘high sugar’ could leave him where we was now. In a hospital bed, unable to walk, unable to work, simply wishing that he had understood the consequences of poorly controlled diabetes before it was too late.
About a year later, I took care of a Hispanic patient who was hospitalized for kidney failure. He spent 3 days per week going to dialysis across the city. Also unable to work, unable support his family, and unable to understand how his ‘high sugars’ could have him sitting in a hospital bed awaiting a kidney transplant.
It’s challenging for physicians to fully emphasize to patients the detrimental consequences that can arise from diabetes. They often have little to no symptoms. You don’t ‘feel’ it. You just have someone in a white coat telling you that this horrible thing is happening and you have to change your lifestyle, take all these medications, lose weight, sleep better, be less stressed, come to the doctor more often, get your eyes checked, pee in a cup to make sure your kidney is okay, eat less sugar, go on more walks, eat more fiber, try a weight loss medication, stick yourself to check your blood sugar, take your insulin, titrate it properly, titrate it again.
Add to that 1) low health literacy and 2) language barriers—highly relevant to the patients I outlined above—and it can be an uphill battle for doctors to stress the importance of managing (including reversing, treating, and preventing) diabetes without absolutely overwhelming a patient.
Being diagnosed with diabetes (or pre-diabetes) should be a monumental moment in someone’s health journey. It is much more than just your A1c being a little high.
Diabetes shapes your health trajectory is ways both shocking and silent.
And with 14-15% of US adults having diabetes, and another 38-45% having pre-diabetes (1), I think its safe to say that blood sugar control (also called glycemic control) is a major public health crisis shaping the health trajectory of America.
How do we take care of diabetes before its too late?
Physicians try our hardest to emphasize the potential consequences of diabetes—to the heart, brain, eyes, kidneys, GI tract, neurons, and more—in ways that are tangible and understandable to patients.
But given the vast reach of this chronic disease, its often difficult to fit it all into a short office visit (typically primary care who are already far over-stretched for time).
And given the rates of diabetes in our society (I am sure many of us know at least one person), it seems common. But common does not mean normal. Diabetes, despite often having few symptoms, is no where close to being benign. The same is overwhelmingly true for high blood pressure (a story for another day).
Today I will dive into the acute and chronic consequences of diabetes, to provide a resource for people with the disease, have a family member with the disease, or are just curious about why it is so important to prevent.
To raise awareness that diabetes goes far beyond your blood sugar being too high.
The MICRO vascular consequences of diabetes
I want to start with talking about the micro-vascular consequences of diabetes. These are so named because they reflect damage to small blood vessels in the body.
This occurs due to chronically high blood sugar levels that cause damage to the lining of vessels.
There are three major areas to highlight [although there is emerging research of microvascular damage beyond these too]
The eyes
The kidneys
The peripheral nerves
The most important the to understand about the MICRO vascular consequences of diabetes is that strict control of blood sugar (via lifestyle and medications) is critically important for preventing microvascular disease.
Reference: https://link.springer.com/chapter/10.1007/978-981-16-5123-6_3
Diabetic Retinopathy and Glaucoma
Diabetic retinopathy and glaucoma are caused by damage to the eyes in the presence of poorly controlled diabetes.
Retinopathy is vascular (read: blood vessel) damage to the retina (the part of the eye that converts light into neural signals so we can ‘see’) that has no symptoms in the early stages, but can progress to visual impairment and blindness. Most cases are detected during screening exams with an eye doctor (ophthalmologist) that are standard of care for someone with diabetes.
However, diabetic retinopathy remains the #1 cause of visual impairment and blindness in people aged 20-74 in the US.
Glaucoma is a another type of eye disease that leads to destruction of the optic nerve (which carries signals from the eye to the brain) due to increased pressure in the eye. Diabetes is a major risk factor for ‘open-angle’ glaucoma, which starts off without symptoms and can also lead to vision loss over time.
For diabetic eye disease, early screening and blood sugar control are crucial for preventing vision loss.
Diabetic Nephropathy
Diabetic nephropathy is a form of chronic kidney disease (CKD) that occurs in 20-40% of patients with diabetes, caused by chronically high blood sugar.
Once again, diabetic CKD is usually asymptomatic, however, it is still a major cause of end-stage renal disease (called ESRD) in the US, leading to dialysis and kidney transplantation.
In type 2 diabetes, CKD can already be present at the time of diagnosis. This is due to the fact that the pathology (high blood sugar and insulin levels) occurs for years before the official diagnosis of diabetes (when A1c is 6.5% or higher).
Anyone with diabetes who has ever seen a lab test for ‘microalbuminuria’ (fancy word for protein in the urine) is being tested for diabetic CKD. Diabetes causes damage to the membranes in the kidneys that help to filter your blood, causing protein to leak out into the urine, an ominous sign that can lead to kidney failure if left untreated.
Some of the major risk factors include longstanding diabetes, poor glycemic control, and high blood pressure (which can be both a cause and consequence of damage to the kidneys).
Diabetic kidney disease is a problem not just because of how it damages the kidneys, but also its far reaching effects on the body—especially the heart.
The kidneys play a key role in regulating fluid balance in the body, with poor kidney function contributing to volume overload and high blood pressure. It is known to accelerate the development of heart disease and increase risk of heart failure (2).
Diabetic nephropathy also leads to anemia, issues with maintaining proper electrolyte levels, and buildup of toxins (including urea and certain medications).
For diabetic kidney disease, early screening (through urine protein tests) and blood sugar control are critical for preventing CKD and potential need for dialysis.
My patient didn’t know that his diabetes could leave him sitting in a hospital bed with kidney failure. Maybe it was the language barrier. Maybe it was the healthy literacy. Maybe it was the doctor. Regardless of the cause, it needs to change. No patient should be surprised that this is a consequence of not taking care of their diabetes from the day of diagnosis.
Diabetic Neuropathy
Peripheral nerves exist outside of the central nervous system (the brain and spinal cord). They communicate feelings and input from the outside world back to the brain. They also carry information from the brain to the body on how to move.
Diabetic neuropathy is progressive damage to nerves caused by chronically high blood sugar. It typically presents with numbness in the distal extremities (i.e. hands and feet), although many people have no symptoms at all. This type is termed ‘peripheral neuropathy’, and it affects ~ 50% of patients with diabetes.
Every patient with diabetes should be screened for neuropathy (read nerve damage) each year.
My patient mentioned earlier, who had just undergone his second leg amputation, suffered from diabetic peripheral neuropathy that progressed to chronic lower extremity infections. The consequences of this nerve damage can be devastating.
Another important type of neuropathy that affects patients with diabetes is called ‘autonomic neuropathy’, which affects up to 90% of patients with diabetes (!!!). This affects nerves of our autonomic nervous system, which automatically controls our internal bodily functions (like our intestines, our heart, our sexual function, and our bladder).
Examples of autonomic neuropathy are occur with diabetes are constipation, urinary retention (not being able to properly empty the bladder), gastroparesis (damage to nerve fibers in the stomach leading to digestive motility issues), erectile dysfunction, postural hypotension (low BP when you stand up), and irregular cardiac rhythms.
Nerves are everywhere and control nearly every process in our process! They are highly sensitive to chronic hyperglycemia, and thus are often damaged as a byproduct of chronic, poorly controlled diabetes.
The great news is that, again, the key to preventing diabetic nerve damage is maintaining good blood sugar control on a regular basis.
The key to preventing MICRO vascular damage from diabetes is…
…one more time!
Blood. Sugar. Control.
Intense glycemic control is the cornerstone for reducing microvascular complications such as retinopathy (eye), glaucoma (eye), nephropathy (kidney), and neuropathy (nerves, both peripheral and autonomic).
With type 2 diabetes, its important to understand that many of these consequences can be present at the time of diagnosis, highlighting even more so how important it is to prevent and screen diabetes before you reach that magical A1c of 6.5% where we can officially diagnose a patient with this silent but deadly disease.
If you or someone you know has pre-diabetes, these pathophysiologic processes that cause damage to microvascular structures may already be occurring. Management and prevention must start early!
And for those who are diagnosed with diabetes, education of the potential consequences is SO important. Especially for the MICRO vascular consequences (eyes, kidney, and nerves), blood sugar control alongside the assistance of a medical professional is critically important for preventing these from occurring.
The patient is in the driver’s seat, but they have to know the right directions! Working with a healthcare provider including a physician (especially primary care, endocrinology, and cardiology), dietician, and diabetes educators is key to building your knowledge of the disease and then building supportive tools, including lifestyle and medications, which can give you the power back to improve your metabolic health.
I was also going to chat in this post about the MACRO vascular consequences of diabetes, including increased risk of heart disease (coronary artery disease, stroke, peripheral artery disease), but this is already getting long… so that will be a future post!
References
https://pubmed.ncbi.nlm.nih.gov/36586345/
https://pubmed.ncbi.nlm.nih.gov/17699208/