Diabetes is known as a silent killer because its symptoms are
easy to miss, including frequent urination, weight loss and itchy skin.
Although diabetes affects 24 million people in the U.S. only about 18
million actually know that they have it. A simple blood test is all that
is needed to find out.
How Diabetes affects the Brain
Our
understanding of the impact of diabetes on organ function has been
evolving since the discovery of insulin in the 1920s. At that time
insulin was a miracle drug that appeared to cure diabetes, but over time
it became clear that death and disability from diabetes complications
involving the eyes, kidneys, peripheral nerves, heart, and vasculature
could occur even with treatment. With the improvement in diabetes care
over the past 20 years, fewer patients are developing the traditional
diabetes complications. However, as people live long and well with the
disease, it has become apparent that diabetes can alter function and
structure in tissues not typically associated with complications such as
the brain and bone. Alteration in brain structure and function are
particularly of concern because of the impact of dementia and cognitive
dysfunction on overall quality of life.
From large
epidemiological studies, it has been demonstrated that both vascular and
Alzheimer's dementia are more common in patients with type 2 diabetes .
Why this might be true has been difficult to define. Certainly these
patients can be expected to have more risk factors such as previous
cardiovascular disease, history of hypertension, and dyslipidemia than
aged matched control subjects, but when these variables are controlled,
the risk for patients with diabetes appears to be higher than that of
other subject groups. Persistent hyperglycemia appears to play an
important role in cerebral dysfunction. Many years ago, Reaven demonstrated that performance on cognitive tasks assessing learning,
reasoning, and complex psychomotor performance was inversely related to
glycemic control in a small population of subjects with type 2 diabetes.
This issue was recently readdressed in the much larger ACCORD
population, where an elevated A1C was found to be linked to reduced
performance on neurocognitive tests assessing memory, learning, and
executive functions in nearly 3,000 subjects with type 2 diabetes .
However, the relevance of these observations to younger patients with
type 2 diabetes and to patients with type 1 diabetes who may have fewer
cardiovascular risk factors is uncertain. Is the dementia and cognitive
dysfunction identified in elderly subjects with type 2 diabetes related
to their comorbidities and age, or is it the result of a
diabetes-related process that begins years earlier?
From
studies performed in adults with type 1 diabetes, we now know that
reductions in measures of motor speed and psychomotor efficiency can be
seen in patients in midlife.These neurocognitive changes have been associated with a reduction in
white matter volume or an alteration in white matter microstructure in
some but not all investigations. Reduction in gray matter density in brain regions responsible for language processing and memory and generalized atrophy have also been identified in young adults with long-standing type 1 diabetes. Patients with chronic hyperglycemia , early onset of disease , or recurrent severe hypoglycemia appear to be at particular risk for the development of changes in brain
structure and function over time, although these associations have not
been consistently observed in all groups of subjects with type 1
diabetes who have been investigated .
If the abnormalities seen in these adults with type 1 diabetes are
specific to diabetes, they may also be seen in younger patients with
type 2 diabetes. Careful assessment of cerebral structure and function
in young adults with type 2 diabetes but without other comorbidities
that increase the risk of vascular disease could help us understand the
impact of diabetes on the brain. Examination of children with diabetes
may also provide more insight into the specific effects of diabetes on
the brain.
In the current issue of Diabetes, Hershey et al. present imaging data collected from a large cohort of children with
type 1 diabetes. They made the surprising observation that hippocampal
volumes were increased in the children with the largest number of severe
hypoglycemic episodes. These observations demonstrate the sensitivity
of the hippocampus to acute hypoglycemia but are contrary to the data
collected in adults with long-standing type 1 diabetes where no changes
in hippocampal volume have been observed . Hershey et al. speculate that the developing brain may respond
differently than the adult brain to a hypoglycemic insult, which has
been demonstrated in animal models where postnatal age influences the
regional vulnerability to hypoglycemia .
Defining
the impact of diabetes and related risk factors on cerebral structure
and function is very important to patients with diabetes. To do so will
require careful prospective evaluation of subjects with type 1 diabetes
over their life span using both sophisticated imaging technology and
comprehensive neurocognitive testing. As depicted in.,
we must understand if the increases in hippocampal volumes seen by
Hershey et al. in children with diabetes and frequent hypoglycemia are
linked to the abnormalities in white matter microstructure and
neurocognitive function identified by Kodl in population of older type 1 diabetic subjects. Of equal importance is
learning whether the structural and neurocognitive abnormalities
identified in midlife in patients with type 1 diabetes are related to
the more severe levels of cognitive dysfunction seen in older subjects
with type 2 diabetes who also experience hypertension, hyperlipidemia,
and vascular disease. If so, we ultimately must determine which
interventions can be used to prevent this progression. These are
critical questions deserving of study in the upcoming years. For the
sake of all people with diabetes, we must not wait to see whether
dementia is the expected outcome in people growing old with diabetes
before we come to understand the full impact of the disease on the
brain.
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हेनरी फोर्ड का जन्म मिशिगैन (Michigan) राज्य के डीयरबॉर्न नामक नगर में हुआ था।16 वर्ष की उम्र में ये घर छोड़कर डिट्रॉइट चले गए। यहाँ कई कारखानों में
काम करके इन्होंने यांत्रिक विद्या का ज्ञान प्राप्त किया। सन् 1886 में ये
घर वापस आए, पिता की दी हुई 80 एकड़ भूमि पर बस गए और वहीं मशीन मरम्मत
करने का एक कारखाना खोला। सन् 1887 में इनका विवाह हुआ तथा इसी वर्ष
इन्होंने गैस इंजिन और खेतों पर भारी काम करनेवाली मशीन बनाने की एक योजना
बनाई, किंतु यंत्रों की ओर विशेष आकर्षण के कारण ये घर पर न टिक सके और फिर
डिट्रॉइट चले आए।
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