Key messages

• Having diabetes probably increases the risk of developing tuberculosis disease to about double the population risk (1.5 to 2.4 times increased risk).
• These results apply to the general adult population; the risk for other groups, such as adolescents and children, is unclear.

What is tuberculosis?

Tuberculosis (TB) is an infection caused by the bacterium Mycobacterium tuberculosis. It primarily affects the lungs but can also affect other sites in the body. TB spreads through the air when a person with TB disease coughs or sneezes. Some people do not develop symptoms after infection, while others develop the disease and symptoms, such as persistent cough, weight loss, fever and night sweats. This is called TB disease.

The diagnosis of TB disease usually involves the administration of a molecular test or culture that detects the bacteria in a bodily secretion (such as sputum (mucus and saliva)) after consultation with a doctor.

TB is a major health concern globally; over 10 million people develop TB disease, and approximately 1.3 million die from the disease every year.

What is diabetes?

Diabetes is a chronic condition characterised by abnormally high blood glucose (sugar) due to inadequate insulin production by the pancreas or the body's inability to properly utilise the insulin it produces, or a combination of both. There are many different types of diabetes; the most frequent is called 'type 2 diabetes mellitus'. Insulin is a hormone that regulates blood sugar. This leads to symptoms such as thirst, frequent urination, tiredness, and slow healing of wounds. Without proper management, diabetes can lead to complications such as heart disease, kidney damage, nerve problems, and eye issues. Managing diabetes involves healthy eating, staying active, taking medicine, and monitoring health parameters to prevent complications.

What did we want to find out?

We wanted to estimate the risk of developing TB disease for people with diabetes compared to those without diabetes.

What did we do?

We looked at studies that included people with and without diabetes over time and compared how frequently each group developed tuberculosis.

What did we find?

We included 48 studies with over 61 million participants from the six WHO regions. However, the representation was variable as we found eight whole-population studies from South Korea, 19 from China, and only one from the African region (Ethiopia). Most studies were in adults, four in children and three in children and adults. On average, the studies followed people for five years.

We found that people with diabetes were at 1.5 to 2.4 times higher risk of developing tuberculosis compared to those without diabetes.

What are the limitations of the evidence?

Many of the studies had limitations. One problem was that many of them used sputum microscopy to diagnose TB in people with symptoms which might have missed some diagnoses. More accurate methods, such as culture or rapid diagnostic tests, currently exist and would miss fewer cases of TB. Moreover, well-defined diagnostic criteria for diabetes, including the type of diabetes and how well-controlled the glucose levels are, are needed to estimate the risk associated with the condition accurately.

How up-to-date is this review?

This evidence is up-to-date as of 3 May 2023.