Eyes, kidneys and nerves

The eyes, kidneys and nerves are affected by damage to small blood vessels, which is why they are often grouped together. This page explains, plainly, what can happen to each one and how common it is. But first, context: what has been happening to these numbers over the last few decades. Context first, then detail. The reverse order tends to produce fear rather than understanding.

The rates have already fallen, a lot

This is the most under-told part of the whole subject.

Kidney failure sits in the low single digits, not the figure people imagine. There is an honest caveat, though: early markers are falling faster than hard endpoints, and one Swedish registry found no clear drop in kidney failure since 2001. The direction is good, but it is not uniform.

Eyes

What happens. The tiny blood vessels in the retina, at the back of the eye, get damaged. In later stages, fragile new vessels can grow and bleed. Fluid can also collect at the centre of vision, and that is the more common cause of sight loss.

How common. Diabetes Canada puts advanced eye disease at about 23%, and fluid at the centre of vision at about 11%, among people with type 1. Those rates have been falling steadily for four decades.

Can it improve? Yes. Early changes can and do regress: improvement was seen in 18% of participants in the largest long-term study. Advanced disease is treatable with laser and injections, and sight is usually preserved.

Clinically meaningful eye changes are rare in the first five years after diagnosis, which is why Canadian screening starts at that point. If you take one action from this section, make it booking the annual eye appointment. It is the highest-value hour in the calendar.

Kidneys

Start with this: in a long-running Boston study, 58% of people with early protein leakage saw it go back to normal over six years. Kidney disease is what people fear most after blindness, and it is the complication on this list most likely to genuinely reverse in its early stage.

It moves slowly, in stages. It usually takes five years or more to pass through each stage. Slow means there is time to act, as long as someone is looking.

Early changes are not rare. Around 15% of people show some protein leakage by 15 years, and 30% by 25 years. These figures come from people who lived with the tools of earlier decades, and early markers like this are the ones falling fastest. Either way, protein leakage is a marker to act on, not a diagnosis of kidney failure.

Kidney failure is the rare end. Roughly 3 to 4% at 25 to 30 years in recent population studies. Dialysis is not the expected destination.

What makes it regress. Blood pressure at target, glucose in range, lower cholesterol, and catching it early. Most of that is medication, not willpower.

Nerves

Longest nerves first. Nerve changes usually start in the feet, then the legs, then the hands. They can show up as burning or shooting pain, or as numbness. Numbness matters more, because losing protective sensation is what makes foot injuries possible.

Read the number carefully. Diabetes Canada says nerve changes are detectable on examination within 10 years in 40 to 50% of people with type 1. "Detectable" is a much wider category than painful or troubling, and symptoms are uncommon in the first five years. Like every rate on this page, it describes people who lived with older tools, and in the DCCT, intensive management lowered the risk of nerve damage at five years by 60%.

Nerves that run the body. The same process can affect the nerves that control heart rate, the bladder and the stomach. Slow stomach emptying (gastroparesis) affects roughly 5% of people over ten years, usually after other complications have appeared.

An honest point. Nerve damage is prevented far better than it is reversed, and slow stomach emptying in particular does not reliably improve even when glucose is in range afterwards. Gastroparesis is the complication most often blamed on the person who has it, and the evidence does not support that blame. Anyone told it is their fault has been told something untrue.

Nerve pain itself is treatable: several medications routinely reduce it by a third to a half.