Study Finds No Link Between Thyroid Function and MCI

Neither clinical nor subclinical hypothyroidism was associated with mild cognitive impairment (MCI), according to a large, population-based study published online ahead of print December 30 in JAMA Neurology.

Among almost 2,000 elderly persons, MCI was present in 16% of those with normal thyroid function, 17% of those with clinical hypothyroidism, and 18% of those with subclinical hypothyroidism, Ajay K. Parsaik, MD, and his colleagues reported.

The findings question the usefulness of pursuing thyroid status as a possible contributor to MCI, wrote Dr. Parsaik, of the Department of Psychiatry and Behavior Sciences, University of Texas Medical School in Houston, and his coauthors.

“Cognitive decline and thyroid dysfunction are common in the elderly, and a widely held view is that hypothyroidism is a reversible risk factor for cognitive impairment, even though several studies have shown no such association,” stated the authors. “Our population-based findings also argue against an association and suggest that neither clinical nor subclinical hypothyroidism is a risk factor for MCI…. This [result] raises questions about the need for routine testing of thyroid function as a part of the diagnostic work-up in patients with MCI.”

The team examined thyroid function and cognitive status among 1,904 elderly subjects who were included in the Olmsted County, Minnesota, health care records database. A total of 1,588 patients (83%) were cognitively normal, and 316 (17%) had MCI. Those with MCI were older (age 82 vs 80), less educated (13 vs 14 years), and more often carriers of the apolipoprotein e4 risk gene (30% vs 22%).

Medical comorbidities, including hypertension, coronary artery disease, diabetes, stroke, and depression, were significantly more common among those with MCI. Most subjects (1,450) had normal thyroid function. Of these, 84% were cognitively normal and 16% had MCI.

Clinical hypothyroidism was present in 313 patients; of these, 83% were cognitively normal, and 17% had MCI. All subjects were taking thyroid replacement therapy. Subclinical hypothyroidism was present in 141 patients; of these, about 83% were cognitively normal and about 18% had MCI. None of these subjects was receiving thyroid replacement therapy.

In an analysis that controlled for age, education, sex, APOE ε4 status, depression, and medical comorbidities, MCI was not significantly associated with either clinical or subclinical hypothyroidism. No significant interaction was observed between APOE ε4 status and hypothyroidism.

The authors noted that their findings should be validated in a larger, longitudinal study in a more varied population.

—Michele G. Sullivan

Neither clinical nor subclinical hypothyroidism was associated with mild cognitive impairment (MCI), according to a large, population-based study published online ahead of print December 30 in JAMA Neurology.

Among almost 2,000 elderly persons, MCI was present in 16% of those with normal thyroid function, 17% of those with clinical hypothyroidism, and 18% of those with subclinical hypothyroidism, Ajay K. Parsaik, MD, and his colleagues reported.

The findings question the usefulness of pursuing thyroid status as a possible contributor to MCI, wrote Dr. Parsaik, of the Department of Psychiatry and Behavior Sciences, University of Texas Medical School in Houston, and his coauthors.

“Cognitive decline and thyroid dysfunction are common in the elderly, and a widely held view is that hypothyroidism is a reversible risk factor for cognitive impairment, even though several studies have shown no such association,” stated the authors. “Our population-based findings also argue against an association and suggest that neither clinical nor subclinical hypothyroidism is a risk factor for MCI…. This [result] raises questions about the need for routine testing of thyroid function as a part of the diagnostic work-up in patients with MCI.”

The team examined thyroid function and cognitive status among 1,904 elderly subjects who were included in the Olmsted County, Minnesota, health care records database. A total of 1,588 patients (83%) were cognitively normal, and 316 (17%) had MCI. Those with MCI were older (age 82 vs 80), less educated (13 vs 14 years), and more often carriers of the apolipoprotein e4 risk gene (30% vs 22%).

Medical comorbidities, including hypertension, coronary artery disease, diabetes, stroke, and depression, were significantly more common among those with MCI. Most subjects (1,450) had normal thyroid function. Of these, 84% were cognitively normal and 16% had MCI.

Clinical hypothyroidism was present in 313 patients; of these, 83% were cognitively normal, and 17% had MCI. All subjects were taking thyroid replacement therapy. Subclinical hypothyroidism was present in 141 patients; of these, about 83% were cognitively normal and about 18% had MCI. None of these subjects was receiving thyroid replacement therapy.

In an analysis that controlled for age, education, sex, APOE ε4 status, depression, and medical comorbidities, MCI was not significantly associated with either clinical or subclinical hypothyroidism. No significant interaction was observed between APOE ε4 status and hypothyroidism.

The authors noted that their findings should be validated in a larger, longitudinal study in a more varied population.

—Michele G. Sullivan

Neither clinical nor subclinical hypothyroidism was associated with mild cognitive impairment (MCI), according to a large, population-based study published online ahead of print December 30 in JAMA Neurology.

Among almost 2,000 elderly persons, MCI was present in 16% of those with normal thyroid function, 17% of those with clinical hypothyroidism, and 18% of those with subclinical hypothyroidism, Ajay K. Parsaik, MD, and his colleagues reported.

The findings question the usefulness of pursuing thyroid status as a possible contributor to MCI, wrote Dr. Parsaik, of the Department of Psychiatry and Behavior Sciences, University of Texas Medical School in Houston, and his coauthors.

“Cognitive decline and thyroid dysfunction are common in the elderly, and a widely held view is that hypothyroidism is a reversible risk factor for cognitive impairment, even though several studies have shown no such association,” stated the authors. “Our population-based findings also argue against an association and suggest that neither clinical nor subclinical hypothyroidism is a risk factor for MCI…. This [result] raises questions about the need for routine testing of thyroid function as a part of the diagnostic work-up in patients with MCI.”

The team examined thyroid function and cognitive status among 1,904 elderly subjects who were included in the Olmsted County, Minnesota, health care records database. A total of 1,588 patients (83%) were cognitively normal, and 316 (17%) had MCI. Those with MCI were older (age 82 vs 80), less educated (13 vs 14 years), and more often carriers of the apolipoprotein e4 risk gene (30% vs 22%).

Medical comorbidities, including hypertension, coronary artery disease, diabetes, stroke, and depression, were significantly more common among those with MCI. Most subjects (1,450) had normal thyroid function. Of these, 84% were cognitively normal and 16% had MCI.

Clinical hypothyroidism was present in 313 patients; of these, 83% were cognitively normal, and 17% had MCI. All subjects were taking thyroid replacement therapy. Subclinical hypothyroidism was present in 141 patients; of these, about 83% were cognitively normal and about 18% had MCI. None of these subjects was receiving thyroid replacement therapy.

In an analysis that controlled for age, education, sex, APOE ε4 status, depression, and medical comorbidities, MCI was not significantly associated with either clinical or subclinical hypothyroidism. No significant interaction was observed between APOE ε4 status and hypothyroidism.

The authors noted that their findings should be validated in a larger, longitudinal study in a more varied population.

—Michele G. Sullivan