This year marks the 111th anniversary of the first observation of Alzheimer’s disease (AD). Although this singular observation may not have been viewed as particularly worrisome on an epidemiologic basis at that time, current facts and figures about AD are more than troublesome . AD has grown at an alarming rate worldwide and such growth is almost certainly tied to increased life expectancy (eg, at age 65, the life expectancy in the US population was about 11.9 years in 1900, 16.5 years in 1980, and 19.2 years in 2009 ) as well as the demographic baby boom after World War II. Currently, about 33.9 million people worldwide (about 5.1 million people in the United States) have AD, and prevalence is expected to triple by 2050 . AD is the sixth-leading cause of death across all ages in the United States, and the fifth-leading cause of death for those age 65 and older . Based on mortality statistics, between 2000 and 2008, deaths from AD have risen by 66%.
AD, frequently termed with the sobriquet of “The Long Goodbye,” is the most common cause of dementia among older people, gradually gets worse over time, irreversibly affects memory, thinking and behavior, and ultimately leads to death in an average of 4 to 8 years (up to 20 years) after diagnosis . Over the duration of the illness, AD patients lose their independence, and require significant assistance from a caregiver. Because of the long duration of the illness and medical care needs, it is evident that AD has a significant impact on health care costs. For all dementias, aggregate payments for health care, long-term care, and hospice care are projected to increase from $183 billion in 2011 to $1.1 trillion in 2050 .
AD is frequently diagnosed at the “mild” stage of the illness, when memory loss worsens and changes in cognitive skills become readily evident (eg, getting lost, trouble handling money, repeating questions, being confused, and taking longer to complete normal daily tasks). The diagnosis of AD is made through physical and neurological exam, mental status testing, neuropsychological testing, and brain imaging including computed tomography, magnetic resonance imaging (MRI), and positron emission tomography examinations . However, diagnostic accuracies vary depending on the imaging technique used as well as the interpretive skills of the doctors . AD diagnosis can be confirmed with complete accuracy only after death with microscopic examination of brain cells.
Even though advances in the understanding of AD have been made in the past 30 years, the root cause(s) of AD still remain a mystery. There is no cure and no preventive therapy available to this day. As in many diseases, early diagnosis of AD would clearly be beneficial for several reasons: planning care and living arrangements, helping preserve function and independence for as long as possible, research on diagnostic tests, and testing new treatments and preventive strategies against the disease. The challenge toward resolving this mystery and thus ending (or at least reducing the impact of) this silent epidemic is enormous for research, and “ if we knew ” what AD is all about and “ what it was we were doing, it wouldn’t be called research, would it? ” (Albert Einstein).
In this issue of Academic Radiology , a team of physicians and scientists from The First Affiliated Hospital of Harbin Medical University and Harbin Institute of Technology (Heilongjiang Province, China) presents a study on MRI for quantifying atrophy of the corpus callosum as a biomarker for the earliest stage of AD . The development of such imaging biomarkers is a critical first step in the battle against AD, and is therefore a worthy topic for this editorial. The study by Zhu et al , and the accompanying editorial, should serve to highlight the importance of having accurate/ precise quantitative measurements for early detection of AD and understanding disease progression, the utility of publicly available databases for research, and the importance of future research toward treatment and preventive care for AD.
Identification of imaging (ie, anatomic and/or physiologic) biomarkers is a critical first step toward understanding the pattern of disease, early diagnosis, disease progression, and assisting in treatment strategy as well as the assessment of treatment effects . Advances in imaging technologies and sophisticated computational processing techniques have rendered the search for AD biomarkers almost unlimited. MRI has become a key examination recommended by physicians when investigating whether the patient has AD. Several studies have confirmed that MRI can reveal patterns of brain atrophy that occur in patients with AD , and rule out other possible causes of cognitive impairment (eg, brain tumor, blood clot).
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