Risk factors for diabetes

The risk factors for type 1 diabetes differ from those for type 2 and gestational diabetes.

Type 1 diabetes

Risk factors include:

• Family history. This increases the chances that a person will have islet-cell antibodies which, in turn, increase the risk of developing type 1 diabetes. Islet cells are clusters of cells in the pancreas that sense blood-glucose levels, and which produce insulin accordingly. Some people’s bodies produce antibodies that attack these cells.
• Race. Type 1 diabetes is more common among certain ethnicities. For example, in the United States, Caucasian people have a greater risk for type 1 diabetes than African-Americans and Hispanic Americans.
• Autoimmune disease. Type 1 diabetes can occur along with other autoimmune diseases like Grave's disease (where the thyroid gland produces too much thyroid hormone) or vitiligo (a condition in which skin pigment is lost).
• Environmental factors. The rising incidence of type 1 diabetes over the past 30 years has been linked to changes in the environment and lifestyle that have only been partially identified. The list of possible factors includes:
  
  Exposure to toxins and chemical compounds
  Toxins in food and water may activate autoimmune mechanisms in genetically susceptible individuals, and so exposure to toxins might result in pancreatic cell death.
  
  The list of elements, man-made chemicals and naturally occurring toxic substances associated with type 1 diabetes is long. One example is arsenic, which occurs naturally in the environment – especially in ground water and contaminated dietary sources. Changes in the metabolism of arsenic is associated with an increased risk of type 1 diabetes in young people.
  
  Infections
  Early studies put the spotlight on viral infections as a potential cause of type 1 diabetes. Several viruses have been implicated in diabetes, with enteroviruses having the strongest evidence from human and animal studies. These viruses are transmitted from person to person via direct contact with virus shed via the gastrointestinal or upper respiratory tract.
  
  According to the findings of a recent study, early respiratory infections are associated with an increased risk of developing type 1 diabetes, with the strongest association found for recurrent viral respiratory infections during the first six months of life. 
  
  Even though bacterial infections are seldomly discussed, these microorganisms are also a potential cause of pancreatic lesions and, ultimately, diabetes.
  
  An imbalance in intestinal microbiota
  Some of the candidate environmental factors for type 1 diabetes (e.g. caesarean delivery and use of antibiotics) are intertwined with the development and functioning of the human microbiome – the microorganisms that live on and in us.
  
  Our gut microbes influence our lipid and glucose metabolism, as well as our immunity and our risk for systemic inflammation outside of the intestine. If these systems aren’t working as they should, there’s a risk for type 1 diabetes.
  
  The ‘hygiene hypothesis'
  This hypothesis suggests that the incidence of autoimmune diseases such as type 1 diabetes may be rising because of improved hygiene and a decreased frequency of childhood infections. In other words, the hypothesis suggests that cleaner living can result in a weakened immune system and, therefore, disease.
  
  For example, some researchers suspect there may be a connection between Finland’s cleanliness and the high incidence of type 1 diabetes in this country.
  
  Not breastfeeding
  Some studies have pointed to a small reduction in the risk of type 1 diabetes with breastfeeding. In particular, children who were still breastfed at the time of introduction to cereals had a reduced risk of type 1 diabetes.
  
  Drinking cow’s milk
  A higher intake of cows’ milk may promote the progression to type 1 diabetes in children with islet autoimmunity because of certain fatty acids present in dairy foods. More research investigating this link is currently underway.
  
  Birth weight and infant growth
  A higher birth weight and rapid weight gain during the first 12-18 months of life have been linked to type 1 diabetes. These findings are small, and the associations have been noted in Scandinavian countries, but not in the USA or Germany. 

Type 2 diabetes 

Risk factors such as genetics and lifestyle choices influence one's chances of developing type 2 diabetes. While factors such as family history, age and ethnicity cannot be changed, we do have control over lifestyle risk factors related to diet, physical activity and weight. 

The following factors can affect your chances of developing type 2 diabetes:

• Overweight/obesity
• Being 45 or older
• A family history of diabetes
• Ethnicity. Type 2 diabetes is up to six times more likely to occur in people of South Asian descent and up to three times more likely in African and Africa-Caribbean people. In the USA, black and Hispanic people are more likely to have diabetes than non-Hispanic whites.
• High blood pressure
• High cholesterol
• A history of gestational diabetes or giving birth to a baby weighing 4kg or more
• Physically inactivity
• A history of heart disease or stroke
• Depression
• Smoking
• Polycystic ovarian syndrome (PCOS)
• Acanthosis nigricans (dark, thick, velvety skin around the neck, armpits or other skin folds)

Recent studies have also linked type 2 diabetes to:

• Gout. This is a form of inflammatory arthritis that develops in some people who have high levels of uric acid in the blood. Two studies have shown that uncontrolled uric acid levels are associated with a nearly 20% increased risk of type 2 diabetes.
• Infertility. Research shows that men with low sperm counts are at higher risk of metabolic disease later in life. This includes type 2 diabetes.
• Chronic hepatitis C infection. In a study done in Taiwan, chronic hepatitis C infection was associated with an increased risk for type 2 diabetes.
• Obesity in children. A recent analysis showed that the number of children and adolescents diagnosed with type 2 diabetes has more than doubled in recent years, and that the increase appears to be coinciding with a rise in obesity rates.
• Poor sleep quality. People with moderate sleep apnoea (where breathing is interrupted during sleep) have a three-fold higher risk of developing diabetes when compared to those without sleep apnoea.
• Impaired lung function. The proposed mechanism that links poor lung function to diabetes is the reduced physical activity that’s often associated with poor lung function. This predisposes to weight gain, leading to the development of the metabolic syndrome – a cluster of biochemical and physiological abnormalities associated with the development of cardiovascular disease and type 2 diabetes.
• Short stature. According to Finnish researchers, short adult stature predicts impaired glucose metabolism and an increased risk of type 2 diabetes and cardiovascular events in men.
• Early or late menopause. Research shows that women who had their final menstrual period before the age of 45 or after age 55 have a higher risk of developing type 2 diabetes compared with those who had their final period between the ages of 46 and 55.
• Job insecurity and irregular shift work. A recent meta-analysis revealed that individuals living under the threat of unemployment and/or on variable incomes have an increased risk of developing diabetes, independent of other factors. This underlines the role of chronic exposure to anxiety and stress in the development of diabetes. Shift work, particularly working night shifts, also disrupts social and biological rhythms as well as sleep, and has been linked to metabolic disorders such as type 2 diabetes.
• Drinking sugary beverages. A study published in the European Journal of Endocrinology indicated that drinking more than two sweetened soft drinks a day doubles the risk of developing two types of diabetes.
• Being on antiretroviral treatment (ART) for HIV/AIDS. The use of some HIV medicines (e.g. those in the nucleoside reverse transcriptase inhibitor class) may increase blood glucose levels and lead to type 2 diabetes.

Gestational diabetes

Gestational diabetes is an increasingly common complication of pregnancy and a large percentage of women who develop it are overweight or obese. Therefore, trying to control your weight before and during pregnancy may help to lower your risk.

Other risk factors for gestational diabetes include:

• Pre-diabetes (higher-than-normal blood glucose levels)
• A history of gestational diabetes
• High blood pressure (hypertension)
• A family history of type 2 diabetes
• Hormone disorders such as polycystic ovary syndrome (PCOS)
• Being older than 25 (the risk is even higher if you’re older than 35)
• Ethnicity. The prevalence of gestational diabetes appears to be particularly high among women from South Asia and South East Asia compared to those who are Caucasian, African-American and Hispanic.
• Previously giving birth to a baby that weighed at least 4,5kg or who had a birth defect
• Previous unexplained stillbirth or miscarriage
• Early onset of menstruation. A study from Australia indicated that girls who get their first period at 11 years of age or younger are at a significantly greater risk of developing gestational diabetes during pregnancy.
• Short stature (<1.50m). In a study done in Brazil, women in the shortest quartile of height (151cm or shorter) had a 60% increased risk for gestational diabetes.
• Thyroid dysfunction during pregnancy. The very latest research shows that women with higher thyroid hormone levels in the first half of pregnancy face an increased risk of gestational diabetes.

Information supplied by Jeannie Berg, diabetes educator and Chairperson of the Diabetes Education Society of South Africa (DESSA), and reviewed by Dr Joel Dave (MBChB PhD FCP Cert Endocrinology), Senior Specialist in the Division of Diabetic Medicine and Endocrinology, University of Cape Town. August 2018.

Read more:
What causes diabetes?