Dr Karen Hansen's Previous Studies

Dr. Hansen has conducted many studies in the past. Read below for more information.

Calcium Absorption Studies

Vitamin D Studies

Other Studies

Studies Completed, Results Pending


Calcium Absorption Studies

Do Proton-Pump Inhibitors Decrease Calcium Absorption

Purpose: The purpose of this study was to investigate if the antacid medicine Omeprazole decreases calcium absorption through the intestine.

Patient Population: We recruited women at least 5 years past menopause who were not taking antacid medication.

Study Design: Women completed two overnight calcium absorption study visits. We gave women omeprazole to take every morning for 30 days. After they completed omeprazole therapy, women completed one last 24-hour visit.

Results: The women's average calcium absorption was 20% ± 10% at the first overnight visit, 18% ± 10% at the second overnight visit and 23% ± 10% following omeprazole therapy. The mean change in calcium absorption from visit one to visit three was 2% ± 7% and from visit two to visit three was 4% ± 8%.

Conclusions: Thirty days of continuous omeprazole therapy did not alter calcium absorption.

Future Directions: Future studies should focus on identifying mechanisms by which omeprazole increases the risk of fracture.

Link to Publication: http://onlinelibrary.wiley.com.ezproxy.library.wisc.edu/doi/10.1002/jbmr.166/pdf

Does Treatment of Hypovitaminosis D Increase Calcium Absorption

Purpose: The purpose of this study was to investigate if correcting mildly low vitamin D levels increased intestinal calcium absorption.

Patient Population: We recruited women at least 5 years past menopause with low calcium intake, vitamin D insufficiency and no history of osteoporosis.

Study Design: Women first completed a 24-hour calcium absorption study visit and then took 50,000 IU of vitamin D per day for 15 days. After confirming that vitamin D levels were in the normal range, women completed a second 24-hour calcium absorption study visit.

Results: Subjects' average vitamin D level was 22 ± 4 ng/mL at the first overnight visit and 64 ± 21 ng/ml at the second overnight visit. Subjects' average calcium absorption was 24 ± 7% at the first overnight visit and 27 ± 6% at the second overnight (p=0.04). Thus, calcium absorption increased by 3 ± 1% after taking vitamin D.

Conclusions: Postmenopausal women with mildly low vitamin D levels can have a small increase in calcium absorption after vitamin D therapy.

Future Directions: Future studies should assess if small increases in calcium absorption favorably affect bone mineral density.

Link to Publication: http://onlinelibrary.wiley.com.ezproxy.library.wisc.edu/doi/10.1359/jbmr.080230/pdf


Vitamin D Studies

Does Treatment of Hypovitaminosis D Increase Calcium Absorption

Purpose: The purpose of this study was to investigate if correcting mildly low vitamin D levels increases calcium absorption through the intestine.

Patient Population: We recruited women at least 5 years past menopause with low calcium intake, vitamin D insufficiency and no history of osteoporosis.

Study Design: Women first completed a 24-hour calcium absorption study visit. Afterwards, women began 50,000 IU vitamin D therapy for 15 days. After confirming that vitamin D levels were in the normal range, women completed a second 24-hour calcium absorption study visit.

Results: Subjects' average vitamin D level was 22 ± 4 ng/mL at the first overnight visit and 64 ± 21 ng/ml at the second overnight visit. Subjects' average calcium absorption was 24 ± 7% at the first overnight visit and 27 ± 6% at the second overnight. Thus, calcium absorption increased by 3 ± 1% after taking vitamin D.

Conclusions: Postmenopausal women with low vitamin D levels can have a small increase in calcium absorption after vitamin D therapy.

Future Directions: Future studies should assess if small increases in calcium absorption favorably affect the skeleton.

Link to Publication: http://onlinelibrary.wiley.com.ezproxy.library.wisc.edu/doi/10.1359/jbmr.080230/pdf

Vitamin D Intake in Elderly Fallers

Purpose: The purpose of this study was to report characteristics of elderly fallers associated with meeting the recommended adequate intake of vitamin D.

Patient Population: Eligible subjects were adults aged 65 and older at high risk of falling.

Study Design: At the beginning and end of the study, researchers recorded all medication and supplement information, including vitamin D intake. Participants received either mailed home safety information or an intervention designed to decrease falls risk. In the intervention group, subjects with a daily vitamin D intake less than 800 IU were asked to increase their intake to 800 IU per day.

Results: Participants who met the recommended adequate intake of vitamin D, compared to those who did not, were younger (76 ± 8 vs 80 ± 7) and had better physical function scores (41 ± 11 vs 39 ± 10). They were also more likely to be female (87% vs 70%), to have had a prior fracture (47% vs 37%) and to take calcium supplements (94% vs 57%).

Conclusions: Older fallers have a low rate of meeting the vitamin D recommended adequate intake, especially men, older individuals, those without prior fracture, and those not taking calcium supplements.

Future Directions: Written instructions and regular telephone follow-up help increase vitamin D intake and may help decrease falls in older adults.

Link to Publication: http://onlinelibrary.wiley.com.ezproxy.library.wisc.edu/doi/10.1111/j.1532-5415.2009.02065.x/pdf

Use of a questionnaire to assess vitamin D status in young adults

Purpose: The purpose of this study was to determine if a questionnaire could help predict young adults with vitamin D deficiency.

Patient Population: We recruited young adults living in Madison, Wisconsin who did not have medical conditions that would affect vitamin D or calcium levels.

Study Design: We gave a questionnaire to young adults. We measured their vitamin D levels

Results: Young adults who repored a suntan,used a tanning booth and drank two or more servings of milk every day were less likely to be deficient in vitamin D.

Conclusions: The questionnaire was moderately useful in identifying young adults with vitamin D deficiency.

Future Directions: Revisions to the questionnaire may help its ability to predict vitamin D deficiency.

Link to Publication: http://www.ncbi.nlm.nih.gov.ezproxy.library.wisc.edu/pmc/articles/PMC2865138/pdf/nihms198051.pdf

The effect of physician workload on an educational intervention to increase vitamin D screening

Purpose: The purpose of this study was to determine if measuring vitamin D in physicians would increase measurement of vitamin D in their patients.

Patient Population: We recruited University of Wisconsin faculty physicians.

Study Design: We measured physicians' vitamin D levels. We mailed physicians a copy of their vitamin D test result. We recorded physicians' frequency of measuring vitamin D in their patients during the 12 weeks before and after receipt of vitamin D test results.

Results: After participating in the study, vitamin D testing frequency increased in family practitioners and internal medicine physicians.

Conclusions: A simple physical intervention had an effect on vitamin D testing rates in physician's patients.

Future Directions: Future educators could use such knowledge to enhance educational interventions toward physicians.

Link to Publication: Link pending


Other Studies

Adherence to alendronate in male veterans

Purpose: The purpose of this study was to investigate adherence rates to osteoporosis therapy in male veterans and to study variables that associated with adherence.

Patient Population: This was a chart review study. Eligible charts were from men who received primary care at the William S. Middleton Memorial Veterans Hospital and who took alendronate (fosamax) for low bone mass.

Study Design: We reviewed subjects' medical records to record patient characteristics that might relate to adherence. We calculated adherence to alendronate as the number of actual prescription fills divided by the number of potential fills over the study interval.

Results: Adherence in the first 12 months of therapy was 59%. Adherence in 24 months of therapy was 54%. Men who were non-adherent were more likely to use tobacco and report side effects. Men who were non-adherent were less likely to have undergone a bone density scan during therapy.

Conclusions: Male veterans who smoke, report side effects and do not have bone density tests are less adherent to alendronate therapy.

Future Directions: Future programs to increase medication adherence could target men with these characteristics.

Link to Publication: http://www.springerlink.com.ezproxy.library.wisc.edu/content/y74p284871780348/


Studies Completed with Results Pending

Do Aromatase Inhibitors Decrease Calcium Absorption

Purpose: Aromatase Inhibitors are used to treat breast cancer, but can also lead to rapid decline in bone mineral density To determine if the class of medicines called aromatase inhibitors decrease calcium absorption.

Patient Population: We recruited women planning to begin an aromatase inhibitor to treat breast cancer.

Study Design: Women completed a calcium absorption overnight visit before starting aromatase inhibitor therapy. Women completed a second calcium absorption overnight visit at least six weeks after starting the aromatase inhibitor.

Prevalence of Hypovitaminosis D in HIV-positive African Adults

Purpose: To determine vitamin D levels in Ugandans who are healthy, who have HIV and who have both HIV and tuberculosis.

Patient Population: We recruited healthy Ugandan adults from the outpatient HIV/Tuberculosis clinic at Mbarara Regional Referral Hospital in Uganda.

Study Design: We measured blood levels of vitamin D, calcium and albumin.

Treatment of Hypovitaminosis D in Rheumatoid Arthritis

Purpose: The purpose of this study was to investigate whether vitamin D therapy improves disease status and bone mineral density in people with rheumatoid arthritis.

Patient Population: We recruited adults with rheumatoid arthritis and mildly low vitamin D levels.

Study Design: Participants received either vitamin D or placebo for one year. Over the course of the year, we assessed rheumatoid arthritis disease activity and bone mineral density.

Predicting Thrombosis in Subjects with Antiphospholipid Antibodies

Purpose: The purpose of this study was to determine if providers could use various risk factors to predict the chance of blood clots in people with antiphospholipid antibody syndrome.

Patient Population: We recruited participants with a diagnosis of antiphospholipid antibody syndrome.

Study Design: Participants underwent a one-time blood draw to test for causes of blood clots. We interviewed subjects to record prior blood clot events and to record risk factors for clotting. In subjects without a previous blood clot, we interviewed them yearly until a blood clot occurred or until five years had passed.

Genetics of Antiphospholipid Antibody Syndrome

Purpose: The purpose of this study was to identify genes that might relate to antiphospholipid antibody syndrome.

Patient Population: We recruited families with at least one member with antiphospholipid antibody syndrome.

Study Design: Family members underwent testing for antiphospholipid antibodies. We interviewed family members and recorded information related to the antiphospholipid antibody syndrome or other autoimmune disease.

The Incidence of Thromboembolic Events in Patients with Antibodies to Heparin-PF4

Purpose: The purpose of this study was to determine how often patients develop antibodies to the drug heparin after undergoing open heart surgery. We evaluated whether or not these antibodies cause low platelet counts and blood clots.

Patient Population: We recruited patients undergoing open heart surgery who received the medicine heparin during the surgery.

Study Design: We collected blood samples from patients before surgery and on two occasions after the surgery. We recorded platelet counts and any clotting events after the surgery.