Continuous Glucose Monitors for Older Adults: Worth It?

How a CGM works

A CGM has three parts:

• A sensor, a tiny flexible filament inserted just under the skin, usually on the back of the upper arm or the abdomen, held by an adhesive patch.
• A transmitter, built in or clipped on, which sends data wirelessly.
• A reader or phone app, which displays the current glucose, a trend arrow and a graph, and may sound alarms.

The sensor measures interstitial fluid glucose, which lags behind blood glucose by about five to fifteen minutes. A sensor lasts from about ten days to two weeks, depending on the model, though some implantable types last longer. After this, it must be replaced. Some systems need occasional finger-prick calibration, though many are factory-calibrated.

Two types are common. Real-time CGM sends constant data and alarms. Intermittently scanned CGM, sometimes called flash monitoring, shows data only when the user scans the sensor with a reader or phone.

What a CGM tells you

• Current glucose and a trend arrow showing whether sugar is rising or falling.
• A graph of the last hours, so you can see the effect of meals, medicines and exercise.
• Alarms for low, very low or high sugar, and in some systems a warning that sugar is predicted to fall soon.
• Time in range: the proportion of time spent within the target range, often 70 to 180 mg/dL for general adults, with different targets for older adults decided by the doctor.
• Overnight patterns, which finger pricks easily miss.

Who may benefit

Guidelines such as the American Diabetes Association's Standards of Care and the NICE guideline NG28 describe CGM mainly for people on insulin, particularly those with type 1 diabetes or those on multiple daily injections, and for people with frequent or severe low sugar. In older adults, a CGM may be helpful for:

• People on insulin with a history of low sugars or hypoglycaemia unawareness. See low blood sugar in older adults.
• Those who live alone and may need alarms to alert a family member.
• People with dementia or frailty whose carers need an easy way to check sugar without repeated finger pricks.
• People who find finger pricks painful or difficult because of arthritis, neuropathy or tremor.
• Those whose sugars swing widely and whose doctor wants more detail.

Who may not benefit

• People on diet alone or low-risk tablets whose lows are unlikely.
• Those who feel overwhelmed by data or alerts. Constant alarms may disturb sleep and raise anxiety.
• Anyone with limited access to a smartphone or reader, or who cannot learn to use it, and has no carer to help.
• Households where the cost cannot be sustained, since stopping and starting a sensor can leave the person with no monitoring at all.

A CGM does not replace a doctor's advice. It gives information; decisions about medicine remain with the doctor.

Advantages over finger pricks

• Fewer finger pricks. Most systems let you treat and decide using the sensor, though a meter is still needed at times.
• Trends and alarms that can prevent lows.
• Overnight data for people at risk of night lows.
• Better pattern spotting for the doctor.
• Easier for carers to check a person who is hard to prick.
• Remote sharing with family by app, if the system allows it. See health devices for a parent far away.

Limits and cautions

• Lag. Sensor readings trail blood glucose, so during fast changes or when a low is suspected, the doctor may advise a finger-prick check.
• Accuracy varies. Readings can differ from meter readings, especially in the first day of a new sensor, with dehydration or poor blood flow, or with compression of the sensor during sleep. Some medicines and high-dose vitamin C can interfere with some sensors. Check the maker's information.
• Skin reactions. Adhesives can irritate fragile, thin or sweaty skin. Rotate sites and ask a nurse for suitable skin care.
• Loose sensors. Sweat, showers, heat and clothing can loosen the patch. Over-patches are available.
• Technology burden. Pairing phones, updating apps and charging readers can be hard for older users without help.
• Alarm fatigue. Too many alerts can lead people to ignore them.
• Cost and supply. Sensors are an ongoing expense and may be hard to find. Costs vary widely, and supply may depend on the city and the seller.
• Not for every situation. Some sensors must be removed before certain scans, such as MRI or CT; ask the doctor.

Practical questions to ask the doctor

• Is a CGM suitable for my parent, given their medicines and risks?
• Which type is best, real-time or scanned?
• What target range and alarm settings should we use?
• Will we still need a meter and strips for confirmation? Usually yes, so keep your kit. See glucometers: how to choose and use one.
• Who will teach the application and who will review the data?
• What happens if a sensor fails or falls off, and how do we get a replacement quickly?
• What is the plan if we cannot afford to continue?

Setting up and using a sensor

Your diabetes team or the maker's trainer should show the steps. In general:

1. Choose a site with enough fat, away from belts, bones, scars and irritated skin. 2. Clean with an alcohol wipe and allow to dry. 3. Apply the sensor using the applicator, as instructed. 4. Start the sensor on the reader or phone and wait for the warm-up period. 5. Use the reader or app to view readings and set alarms as agreed with the doctor. 6. Replace the sensor on schedule and rotate sites.

Dispose of used applicators and sensors safely in a sharps container; see glucose strips and lancets guide.

Indian conditions

Heat, sweating and humidity can loosen adhesives, so keep the skin clean and dry before application, and check the sensor after bathing or long sweaty days. Keep spare sensors in a cool, dry place, away from direct sun. Phones may lose power during power cuts, so keep a power bank handy and charge the reader regularly. Network or app issues can interrupt remote sharing, so agree a back-up plan with the family. Check that the maker has a local service channel and a way to replace faulty sensors. Because supply chains can break, keep one spare sensor and an adequate stock of strips.

Cost and value

CGM costs can be significant and recurring. Weigh them against benefits, such as fewer severe lows, fewer emergency visits and more peace of mind. If the doctor recommends a CGM for safety, it may be worthwhile; if it is for general curiosity, a simple meter and good log may do. See health device budgets and quality checks in India.

Using the data wisely

Looking at the graph every few minutes can cause anxiety. Agree with the doctor how often to check, what actions to take at certain alarms and when to call. Share reports with the doctor at visits; many systems produce summary reports. Never adjust insulin or tablets on your own based on the sensor, even if the readings look worrying; phone the doctor. See using home readings in a teleconsultation.

When to ask a professional

Ask a diabetes specialist, endocrinologist or diabetes educator whether a CGM is appropriate and to teach safe use. Ask for help if alarms fire repeatedly, if sensor readings and meter readings disagree, if the skin becomes red, swollen or painful under the patch, or if your parent feels unwell despite normal sensor readings. Call 112 for unresponsiveness, seizure or inability to swallow.