We're unable to sign you in at this time. Please try again in a few minutes.
We were able to sign you in, but your subscription(s) could not be found. Please try again in a few minutes.
There may be a problem with your account. Please contact the AMA Service Center to resolve this issue.
Contact the AMA Service Center:
Telephone: 1 (800) 262-2350 or 1 (312) 670-7827  *   Email: subscriptions@jamanetwork.com
Error Message ......
Editor's Correspondence |

Investigating Factors of Decline in Cognitive Function or Dementia—Reply

David J. Llewellyn, PhD; Kenneth M. Langa, MD, PhD; Iain A. Lang, PhD; David Melzer, PhD
Arch Intern Med. 2011;171(3):267. doi:10.1001/archinternmed.2010.530.
Text Size: A A A
Published online


In reply

In response to Dr Mozaffarian, it is correct that our prospective observational study1 does not demonstrate causality. We do not suggest at any point that we have demonstrated causality. Indeed, our main conclusion is that further prospective studies and randomized controlled trials are now needed. Similarly, we identified that vitamin D may have therapeutic potential in this context. Again, supplementation trials are now needed to establish whether this is the case. We also acknowledge the possibility of reverse causality—in short, people with preexisting dementia may have low levels of vitamin D at baseline and also be susceptible to further cognitive decline. This hypothesis is testable, and we established that excluding people with dementia at baseline and controlling for impaired mobility did not change the pattern of associations. Furthermore, there was no statistical interaction between baseline cognition and vitamin D levels, suggesting that the association was not driven by people with poor cognitive function at baseline. There were a number of differences between participants grouped by serum 25(OH)D levels at baseline as we would expect, including total energy intake. These differences were controlled for in fully adjusted models and did not change the pattern of results. Given the wealth of evidence from animal and in vitro experiments to suggest that vitamin D has a wide range of biological functions throughout the human body, including neuroprotection, we do not accept that an association with cognitive decline or nonskeletal diseases is “intuitively unlikely.”

Sign in

Purchase Options

• Buy this article
• Subscribe to the journal
• Rent this article ?

First Page Preview

View Large
First page PDF preview





Also Meets CME requirements for:
Browse CME for all U.S. States
Accreditation Information
The American Medical Association is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The AMA designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 CreditTM per course. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Physicians who complete the CME course and score at least 80% correct on the quiz are eligible for AMA PRA Category 1 CreditTM.
Note: You must get at least of the answers correct to pass this quiz.
Please click the checkbox indicating that you have read the full article in order to submit your answers.
Your answers have been saved for later.
You have not filled in all the answers to complete this quiz
The following questions were not answered:
Sorry, you have unsuccessfully completed this CME quiz with a score of
The following questions were not answered correctly:
Commitment to Change (optional):
Indicate what change(s) you will implement in your practice, if any, based on this CME course.
Your quiz results:
The filled radio buttons indicate your responses. The preferred responses are highlighted
For CME Course: A Proposed Model for Initial Assessment and Management of Acute Heart Failure Syndromes
Indicate what changes(s) you will implement in your practice, if any, based on this CME course.


Some tools below are only available to our subscribers or users with an online account.

0 Citations

Sign in

Purchase Options

• Buy this article
• Subscribe to the journal
• Rent this article ?

Related Content

Customize your page view by dragging & repositioning the boxes below.

Articles Related By Topic
Related Collections
PubMed Articles

The Rational Clinical Examination: Evidence-Based Clinical Diagnosis

The Rational Clinical Examination: Evidence-Based Clinical Diagnosis
Domains Tested by Screening Instruments