MIAMI BEACH – Nondipping of nighttime blood pressure – a recognized risk factor for hypertension – emerges as early as adolescence, preferentially affects blacks, and is associated with lower socioeconomic status, according to a study.
In addition, negative psychological attributes such as trait anger and interpersonal conflict by day were independent factors for blood pressure nondipping at night, Tanisha I. Burford, Ph.D., said at the annual meeting of the International Society on Hypertension in Blacks.
Tanisha Burford, Ph.D.
Dr. Burford recommended asking potentially at-risk adolescent patients about their sleep quality, because those with fragmented or interrupted sleep are less likely to experience a normal, nocturnal restorative decline in blood pressure.
She also suggested that clinicians consider asking at-risk adolescents to wear an ambulatory blood pressure monitor for more-comprehensive, real-time feedback on circadian blood pressures, compared with conventional intermittent clinical readings.
Dr. Burford and her colleagues did just that – they asked 139 black and 106 white healthy adolescents to wear ambulatory blood pressure monitors for 48 consecutive hours.
"Most of what we know about nondipping blood pressure is [from studies] in adults." There is some evidence that blunting of blood pressure decreases at night "emerges early in the life course, during adolescence, and even in some children 9-11 years old," said Dr. Burford, a postdoctoral scholar in the cardiovascular behavioral medicine research program at the University of Pittsburgh.
Study participants used electronic diaries to rate social interactions and any conflict (on a 6-point scale) in the 10 minutes preceding each blood pressure reading. They also completed standard measures of depression (Center for Epidemiologic Studies Depression scale or CES-D); trait anger (State Trait Anxiety Inventory or STAI), and negative affect (Positive and Negative Aspect Schedule or PANAS).
The researchers found a higher ratio of average night to day blood pressures (both systolic and diastolic) among black teenagers who reported higher rates of negative emotions and/or conflict compared to white teenagers in a regression analysis that adjusted for age, sex, and body mass index.
"Most of this is a systolic effect – which makes sense for hypertension – [where] systolic changes are more detrimental in early stages," Dr. Burford said.
Among blacks, the beta value (the interaction between average systolic blood pressure night/day ratio and race) was a significant 0.43 for trait anger; a significant 0.52 for negative affect; and a significant 0.59 for depression.
The interaction between interpersonal stress and race had a nonsignificant trend for an adverse effect on the systolic blood pressure ratio (beta value, 0.38).
"The most fascinating thing is that these negative psychological attributes did [interact with] race," Dr. Burford said. Trait anger, depression, and conflict were only associated with nighttime nondipping of blood pressure among black teens, even though white teens reported higher levels of trait anger. A possible explanation, she added, was that positive attributes were less protective for black teenagers.
Some blacks have a "lower resource capacity," Dr. Burford said, which could include lower levels of self-esteem and less social support, particularly if they live in a stressful environment.
Participants were 14-19 years old (median, 16 years) and part of the Pittsburgh Project Pressure II.
Typically, blood pressure is low during the morning, increases during the day, and then drops at nighttime. Nondipping nighttime blood pressure was defined as less than a 10% decrease vs. daytime pressures. Although blood pressure readings can be highly variable and influenced by multiple factors, this 10% or less cutoff is a reliable predictor of risk, Dr. Burford said.
Dr. Burford had no relevant financial disclosures.