Social determinants of ethno-racial inequalities in substance use: a decomposition of national survey data

Background

Similar to the US, mortality due to suicide and the use of opioids, alcohol, and other substances (so-called “Deaths of Despair”), is rising in Canada and has been disproportionately observed among Whites compared to other racial and ethnic groups. This study aimed to assess the determinants of the ethno-racial differences in the use of substances that underlie these deaths.

Methods

Using nationally representative data from the Canadian Community Health Survey (2003, 2015–2016, 2018 cycles), a decomposition analysis was performed to estimate the contribution of psychosocial determinants, including age, sex, marital status, immigration, education, income, rurality, and affective health on inequalities between White and non-White populations in illicit substance, opioid, and problematic alcohol use and combined use (≥ 2) of substances.

Results

Overall, White respondents reported higher levels (by 5% to 10%) of substance use than non-White peers. Over 30% of the ethno-racial inequalities in illicit substance, problematic alcohol, and polysubstance use are explained by the protective role of immigration among those who are not White, whose low levels of substance use lower the prevalence in the non-White population overall. Among those born in Canada, no ethno-racial differences in substance use were observed.

Conclusion

Social determinants, particularly immigrant status, explain a substantial proportion of ethno-racial inequalities in substance use in Canada. The jump in substance use between racialized populations who immigrated to Canada and those Canadian-born highlights the importance of exploring within-group variability in deaths of despair risk and considering how intersecting forces including systemic racism shape substance use patterns across generations.

     

An uncertainty principle for neural coding: Conjugate representations of position and velocity are mapped onto firing rates and co‐firing rates of neural spike trains

The hippocampal system contains neural populations that encode an animal's position and velocity as it navigates through space. Here, we show that such populations can embed two codes within their spike trains: a firing rate code ( R ) conveyed by within‐cell spike intervals, and a co‐firing rate code () conveyed by between‐cell spike intervals. These two codes behave as conjugates of one another, obeying an analog of the uncertainty principle from physics: information conveyed in R comes at the expense of information in , and vice versa. An exception to this trade‐off occurs when spike trains encode a pair of conjugate variables, such as position and velocity, which do not compete for capacity across R and . To illustrate this, we describe two biologically inspired methods for decoding R and , referred to as sigma and sigma‐chi decoding, respectively. Simulations of head direction and grid cells show that if firing rates are tuned for position (but not velocity), then position is recovered by sigma decoding, whereas velocity is recovered by sigma‐chi decoding. Conversely, simulations of oscillatory interference among theta‐modulated “speed cells” show that if co‐firing rates are tuned for position (but not velocity), then position is recovered by sigma‐chi decoding, whereas velocity is recovered by sigma decoding. Between these two extremes, information about both variables can be distributed across both channels, and partially recovered by both decoders. These results suggest that populations with different spatial and temporal tuning properties—such as speed versus grid cells—might not encode different information, but rather, distribute similar information about position and velocity in different ways across R and . Such conjugate coding of position and velocity may influence how hippocampal populations are interconnected to form functional circuits, and how biological neurons integrate their inputs to decode information from firing rates and spike correlations.     

Extremes of weight gain and weight loss with detailed assessments of energy balance: Illustrative case studies and clinical recommendations

Extreme weight changes, or changes in weight greater than 10 kg within a 2-year period, can be caused by numerous factors that are much different than typical weight fluctuations. This paper uses two interesting cases of extreme weight change (a female who experienced extreme weight gain and a male who experienced extreme weight loss) from participants in the Energy Balance Study to illustrate the physiological and psychosocial variables associated with the weight change over a 15-month period, including rigorous assessments of energy intake, physical activity (PA) and energy expenditure, and body composition. In addition, we provide a brief review of the literature regarding the relationship between energy balance (EB) and weight change, as well as insight into proper weight management strategies. The case studies presented here are then placed in the context of the literature regarding EB and weight change. This report further supports previous research on the importance of regular doses of PA for weight maintenance, and that even higher volumes of PA are necessary for weight loss. Practitioners should emphasize the importance of PA to their patients and take steps to monitor their patients’ involvement in PA.