In This Issue of Archives of Internal Medicine FREE

Kim et al estimated radiation doses and associated cancer risks from coronary artery calcification screening with multidetector computed tomography, according to patient age, frequency of screening, and scan protocol. The radiation dose from a single coronary artery calcification computed tomographic scan varied more than 10-fold (effective dose range, 0.8-10.5 mSv) depending on the protocol. Assuming screening every 5 years from the age of 45 to 75 years for men and from age 55 to 75 years for women, the estimated excess lifetime cancer risk using the median dose of 2.3 mSv (range, 0.8-10.5 mSv) was 42 cases per 100 000 men (range, 14-200 cases) and 62 cases per 100 000 women (range, 21-300 cases). These radiation risk estimates can be compared with potential benefits from screening, when such estimates are available. Doses and therefore risks can be minimized by using optimized protocols.

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Little is known about whether lifestyle exercise, such as walking or biking to work, confers cardiovascular benefits. In this study by Gordon-Larsen et al, 2364 adults from the Coronary Artery Risk Development in Young Adults (CARDIA) study were examined. In multivariable analyses controlling for age, race, income, education, smoking, examination center, and physical activity excluding walking, active commuting was positively associated with fitness in men and women and inversely associated with body mass, obesity, triglyceride level, blood pressure, and insulin level in men. Findings suggest that active commuting should be investigated as a form of lifestyle exercise for maintaining or improving health.

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Vitamin K antagonists are effective for the prevention of arterial thromboembolism in patients with mechanical heart valves, atrial fibrillation, and myocardial infarction but increase the bleeding risk. Torn et al calculated international normalized ratio–specific incidence rates of bleeding and thromboembolic events in a large group of routinely treated patients to determine the optimal intensity of oral anticoagulation at which the total incidence of untoward events is minimized.

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Sink et al examined the relationship between exposure to angiotensin-converting enzyme (ACE) inhibitors (as a class and categorized by ability to cross the blood brain barrier) and incident dementia, cognitive decline, and incident disability in daily functioning (IADL) in 1054 hypertensive older adults followed for a median of 6 years. Duration of exposure to ACE inhibitors as a class vs other antihypertensive classes was not associated with a reduction in risk of dementia. However, when examined by central activity, exposure to ACE inhibitors that cross the blood-brain barrier was associated with a 65% reduction in cognitive decline per year of exposure, while exposure to ACE inhibitors that do not cross the blood-brain barrier was associated with significantly greater risk of incident dementia and incident IADL disability compared with other antihypertensive agents. There may be important within-class differences in the association between ACE inhibitors and cognition, favoring centrally active agents.

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Gross et al conducted a randomized clinical trial of modified directly observed therapy (mDOT) in human immunodeficiency virus type 1 (HIV-1)–infected individuals starting their first lopinavir/ritonavir–based antiretroviral regimen. The experimental arm (n = 82) had 2 phases: (1) active mDOT phase, which was administered by medically allied personnel approved by the site Monday through Friday for 24 weeks, and (2) post-mDOT phase, during which the medications were self-administered for the second 24 weeks. The control arm (n = 161) had self-administered therapy for the entire 48 weeks. The experimental arm had a 7% higher rate of treatment success than the control arm during the first 24 weeks, when the mDOT was in place, but this difference did not achieve statistical significance. After mDOT was discontinued, the treatment success rate was somewhat lower in the experimental arm than in the control arm, although this difference was also not statistically significant. The authors conclude that mDOT should not be incorporated into standard care for treatment-naïve HIV-1–infected individuals.

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