Sleep and high-risk behavior in military service members: a mega-analysis of four diverse U.S. Army units

Experimental sleep restriction and deprivation lead to risky decision-making. Further, in naturalistic settings, short sleep duration and poor sleep quality have been linked to real-world high-risk behaviors (HRB), such as reckless driving or substance use. Military populations, in general, tend to sleep less and have poorer sleep quality than nonmilitary populations due to a number of occupational, cultural, and psychosocial factors (e.g. continuous operations, stress, and trauma). Consequently, it is possible that insufficient sleep in this population is linked to HRB. To investigate this question, we combined data from four diverse United States Army samples and conducted a mega-analysis by aggregating raw, individual-level data (n = 2,296, age 24.7 ± 5.3). A negative binomial regression and a logistic regression were used to determine whether subjective sleep quality (Pittsburgh Sleep Quality Index [PSQI], Insomnia Severity Index [ISI], and duration [h]) predicted instances of military-specific HRB and the commission of any HRB (yes/no), respectively. Poor sleep quality slightly elevated the risk for committing HRBs (PSQI Exp(B): 1.12 and ISI Exp(B): 1.07), and longer duration reduced the risk for HRBs to a greater extent (Exp(B): 0.78), even when controlling for a number of relevant demographic factors. Longer sleep duration also predicted a decreased risk for commission of any HRB behaviors (Exp(B): 0.71). These findings demonstrate that sleep quality and duration (the latter factor, in particular) could be targets for reducing excessive HRB in military populations. These findings could therefore lead to unit-wide or military-wide policy changes regarding sleep and HRB.

Social anxiety and alcohol-related negative consequences among college drinkers: do protective behavioral strategies mediate the association?

The link between social anxiety and alcohol-related negative consequences among college students has been well documented. Protective behavioral strategies are cognitive-behavioral strategies that college students use in an effort to reduce harm while they are drinking. In the current study we examined the mediating role of the 2 categories of protective behavioral strategies (i.e., controlled consumption and serious harm reduction) in the relationship that social anxiety symptoms have with alcohol-related negative consequences. Participants were 572 undergraduates who completed measures of social anxiety, alcohol use, negative consequences of alcohol use, and protective behavioral strategy use. Only serious harm reduction strategies emerged as a mediator of the association that social anxiety symptoms had with alcohol-related negative consequences. Clinical and research implications are discussed.

Social anxiety symptoms and drinking behaviors among college students: the mediating effects of drinking motives

The impact of social anxiety on negative alcohol-related behaviors among college students has been studied extensively. Drinking motives are considered the most proximal indicator of college student drinking behavior. The current study examined the mediating role of drinking motives in the relationship that social anxiety symptoms have with problematic (alcohol consumption, harmful drinking, and negative consequences) and safe (protective behavioral strategies) drinking behaviors. Participants were 532 undergraduates who completed measures of social anxiety, drinking motives, alcohol use, harmful drinking patterns, negative consequences of alcohol use, and protective behavioral strategy use. Our results show that students with higher levels of social anxiety symptoms who were drinking for enhancement motives reported more harmful drinking and negative consequences, and used fewer protective behavioral strategies. Thus, students who were drinking to increase their positive mood were participating in more problematic drinking patterns compared with students reporting fewer social anxiety symptoms. Further, conformity motives partially mediated the relationship between social anxiety symptoms and negative consequences. Thus, students with more symptoms of social anxiety who were drinking in order to be accepted by their peers were more likely than others to experience negative consequences. Clinical and research implications are discussed.

In vitro and in vivo comparison of two-, three- and four-point Dixon techniques for clinical intramuscular fat quantification at 3 T

OBJECTIVE

To compare Dixon-based MRI techniques for intramuscular fat quantification at 3 T with MR spectroscopy (MRS) in vitro and in vivo.

METHODS

In vitro, two- three- and four-point mDixon (Philips Medical Systems, Best, Netherlands) sequences with 10°, 20° and 30° flip angles were acquired from seven test phantoms with sunflower oil-water percentages of 0-60% sunflower oil and calculated fat-water ratios compared with MRS. In vivo, two- three- and four-point mDixon sequences with 10° flip angle were acquired and compared with MRS in the vastus medialis of nine healthy volunteers (aged 30.6 ± 5.3 years; body mass index 22.2 ± 2.6).

RESULTS

In vitro, all mDixon sequences correlated significantly with MRS (r > 0.97, p < 0.002). The measured phantom percentage fat depended significantly on the flip angle (p ≤ 0.001) and mDixon sequence (p = 0.005). Flip angle was the dominant factor influencing agreement with MRS. Increasing the flip angle significantly increased the overestimation of the mDixon sequences compared with MRS. In vivo, a significant difference was observed between sequences (p < 0.001), with all mDixon sequences overestimating the intramuscular fat content of the vastus medialis muscle compared with MRS. Two-point mDixon agreed best with MRS and had comparable variability with the other mDixon sequences.

CONCLUSION

This study demonstrates that mDixon techniques have good linearity and low variability for use in intramuscular fat quantification. To avoid significant fat overestimation with short repetition time, a low flip angle should be used to reduce T1 effects.

ADVANCES IN KNOWLEDGE

This is the first study investigating the optimal mDixon parameters for intramuscular fat quantification compared with MRS in vivo and in vitro.