Mrs Sara is a 75-year-old woman with Type 1 Diabetes and is living with her 78- year-old husband Mr John. Mrs Sara's doctors have instilled in her the practice of maintaining tight sugar control from the beginning. By the time she was married, she had already mastered the carbohydrate counting and could estimate the amount of Insulin requirement by taking one quick look at the food plate.About 10 years ago, she started developing forgetfulness. At first, it was thought as a normal sign of ageing by her family. With time, her forgetfulness increased. About 5 years ago, at the age of 70, she forgot the way to her friend's house, where she had been going regularly every week for the past several years. She stopped handling household groceries and stopped doing her favourite hobby, painting. She found it difficult to express her thoughts, feelings and desires.Mrs Sara also experienced trouble in using the right words for everyday objects. For example, when looking for her wristwatch, she asked where her hand wall clock is. Now she has reached a stage where she is unable to take insulin by herself, which was her second nature. Mrs Sara is aware that she needs to take something before food, but is unable to remember and comprehend what it is. Mr John being old himself, is unable to take care of her. Mrs Sara's personality and behaviour have also continued to deteriorate over time. Nowadays, she is unable to recognise Mr John to whom she has been married for the past 50 years.Mrs Sara is suffering from Alzheimer's disease since the age of 65. Her doctor explained to Mr John that there are medications that may relieve the symptoms to some extent but there is no cure to Alzheimer's disease at present.DementiaDementia refers to a progressive decline in the functioning of the brain affecting the thinking skills, behaviour, memory and social abilities of a person. People with dementia forget the most common and oft- repeated activities such as doing daily chores, going back home, taking medication, names of friends and family etc. Their expressions and behaviour may change over time and they may find it difficult to take care of themselves.Dementia affects a person's perception of the surroundings, communication and his or her ability to think and solve a problem.Dementia occurs when healthy neurons stop functioning in the brain and are unable to connect with other brain cells. This causes the neurons to die. Irreversible dementia can be categorised into five types- Alzheimer's disease, Lewy body dementia, vascular dementia, frontotemporal dementia and mixed dementia, wherein a combination of two or more types of dementia is found.In India, more than 4 million people have some form of dementia. While dementia is commonly observed in people when they grow older, it is not a part of the process of ageing. Some types of dementia may occur in people in their middle age. For example, in frontotemporal dementia, a person may show changes in his or her personality, language and behaviour during his or her middle age..Alzheimer's diseaseAlzheimer's disease is the most common form of dementia. At first, a person with Alzheimer's disease may experience mild confusion and difficulty remembering things. Over time, this forgetfulness increases and hampers the behaviour of a person. Though the exact cause of Alzheimer's disease is unknown, one of the signs of Alzheimer's disease results from a deposition of amyloid protein on the nerve cells, leading to the death of the cells and an impairment of nerve signal transmissions. Depending on the area of the brain involved, different functions like thinking and communication skills, problem-solving skills, memory, attention and focus are affected. Initially, the ability to learn new things, i.e., recent or short-term memory is affected. With the progression of the disease, the long-term memory is also hampered.Many people with Alzheimer's disease are diagnosed in a moderate stage where they may have a temporary lapse of memory, difficulty handling matters like finances and organising their thoughts and expressing themselves. As the disease progresses, people with Alzheimer's disease can have a change in personality and behaviour. They eventually stop recognising friends and family members.People with Alzheimer's disease may live on an average of 8 years but some people may survive up to 20 years. There are medications that may relieve some of the symptoms of the condition. Along with medication, psychiatric counselling, speech therapy and cognitive exercises such as puzzles, crossword and learning to play a musical instrument may also be helpful..Vascular dementiaDiabetes is a condition characterised by high sugar levels in the blood either due to insulin deficiency or inefficient insulin action. Type 1 Diabetes is an autoimmune condition caused by the destruction of beta cells in the pancreas which are responsible for the production of insulin. Type 2 Diabetes is caused by insulin resistance, i.e., the produced insulin is either inefficient or insufficient to lower the sugar levels in the blood. Uncontrolled blood sugar levels may result in diabetic complications affecting eyes, heart, kidneys and nerves.Vascular dementia refers to a decreased functioning of the blood vessels due to high blood sugar levels. This affects the blood supply in the blood vessels and leads to nerve tissue death. Blood sugar fluctuations may affect the blood vessels in the brain, similar to those in the eyes, kidney and the heart. When a tiny blood vessel ruptures in the brain, it causes a sudden drop in the cognitive ability, which stabilises until another rupture of the blood vessel. This leads to a gradual but progressive decline in the functioning of the brain.IncidenceA 2013 study had shown that the risk of developing vascular dementia and Alzheimer's disease increases from 5 to 7 per cent in adults of age 60 and over. The risk of Alzheimer's disease risk increases once people reach 65 and thereafter it doubles every 5 years. With better management of Diabetes, longevity has increased and now more people with diabetic complications are being seen.Many research studies have recommended that cognitive dysfunction should be listed as one of the complications of Diabetes along with the complications of the eyes, nerves, kidney and the heart.Risk factorsRisk factors like obesity, hypertension and high cholesterol associated with Diabetes are also linked to dementia. Many research studies have shown that people with Diabetes have a high risk of developing dementia than people without Diabetes. People who had a stroke recently or who have a history of stroke have an increased risk of developing vascular dementia in later life. The protein deposition in Alzheimer's disease may hinder insulin receptors and prevent the entry of sugar into the nerve cells. This may lead to deterioration of the brain cells. Smoking may also up the risk of dementia. In rare cases, vascular dementia may be caused by genetic disorders in which the person may have a family history of strokes.Low blood sugar levelsTight blood sugar control may sometimes cause episodes of low blood sugar (hypoglycaemia) which is very harmful to the brain. As the brain requires glucose to function properly, its deprivation results in cognitive impairment. Even though the adult brain is resilient to low sugar episodes unlike very young children, repeated hypoglycemic episodes may result in cumulative brain damage which can be permanent. In fact, studies have shown that MRI done during episodes of severe hypoglycaemia leading to comatose in people with Diabetes had showed reduced grey matter in some parts of the brain.PreventionPeople with Diabetes should keep their blood sugar levels under control and should take their Diabetes medications on time.They should maintain a healthy lifestyle like staying active and engaged, eating healthy, not smoking, exercising which includes brisk walking 30 minutes a day. They should have their blood pressure and cholesterol under control as well. If people are overweight or obese, they should try to lose some weight. Managing blood sugar level, blood pressure, cholesterol and weight not only helps in preventing heart problems, kidney and eye problems but also may help in preventing or postponing dementia.To concludeDiabetes during the middle age doubles the risk of dementia in later life. Dementia begins with forgetfulness and progresses to loss of function, slowly over a period of years, when people become totally dependent on others for their care. Active lifestyle, controlled blood sugar levels, blood pressure and cholesterol can help prevent or at least postpone cognitive decline for a long time. Caregivers need to understand that cognitive decline is irreversible and that they need to change their strategy in taking care of people with dementia rather than expecting them to change.Dr Sugathi Kumaran is a consultant physician.