1. Alex Dregan and Martin Gulliford King’s College London 09 March 2012 Illicit drug use and cognitive functioning in mid-adult years

2. Presented by Background -Long-term illicit drug use may be associated with impaired short-term and working memory, word fluency, attention span, and cognitive flexibility. -Other studies found no association between illicit drug use and executive functioning and working memory. -The relation has not been thoroughly investigated, and the evidence is rather inconclusive, short-term and methodologically flawed. -Methodological issues: differences in sampling methods, the types of drugs studied, cognitive outcome measures, and length of follow-up. Alex Dregan

3. Presented by Study aims - What is the long-term impact of illicit drug use on cognitive functioning? - Are diverse drugs differentially related to cognitive imapirment? - Is there evidence for a dose-response relationship? Alex Dregan

4. Presented by Data -National Child Development Study(NCDS) includes all children born in the UK during the first week of March 1958 (N=17,415) - Multiple follow-up surveys (birth, ages 7, 11, 16, 23, 33, 42, 46 and most recently age 50) gathering data on a broad range of psycho-social outcomes. -Illicit drug use –data on 12 drugs collected retrospectively and prospectively from age 16 to age 42. -Cognitive outcome measures collected at age 50: global cognition, memory functioning, and executive functioning. Alex Dregan

5. Presented by Statistical analysis - All cohort members who took part in the age 42 (N=11,419) survey. - Predictors – current and past illicit drug use (yes/no), class drugs (high-risk, intermediate, low-risk), length of use and type (ie cannabis, coke, heroin, LSD, amphetamine etc). -Multiple logistic regression analyses to predict illicit drug usage at age 42. -Multivariate linear regression to estimate the impact of current and past illicit drugs on cognitive outcomes at age 50 adjusting for age 42 covariates. -Missing data –separate missing category for each predictor. Alex Dregan

6. Presented by RESULTS 6 Alex Dregan

7. Presented by Illicit drug use at 42 years of age in the study population (N=11,419) Alex Dregan

8. Presented by Adjusted ORs (CIs) of predictors for illicit drug use at age 42 Current drug useEver drug use Poor health (vs. good)1.54(1.21,1.96)1.12(0.95,1.32) College degree (vs. no qualif.)1.87(1.43,2.46)3.31(2.80,3.92) Smoker (yes/no)4.33(3.17,5.92)6.26(5.05, 7.74) Alcohol problems1.96(1.64,2.33)2.03(1.79,2.30) Depression (yes/no)1.42(1.17,1.74)1.30(1.14,1.48) Single (vs. married)2.55(2.18,2.98)1.95(1.77,2.16) Low social class (vs high)0.86(0.67,1.11)0.72(0.66,0.90) Female (vs male)0.52(0.44,0.61)0.52(0.47,0.57) Alex Dregan

9. Presented by Adjusted OR for predictors for different illicit drug classes at age 42 High riskIntermediate riskLow risk Poor health (vs. good)1.07(0.64,1.77)1.39(1.07,1.90)2.27(1.46,3.53) Long-standing illness1.02(0.64,1.62)1.20(0.94,1.53)1.88(1.23,2.89) College degree (vs. no qualif.) 2.22(1.25,3.92)1.77(1.32,2.36)1.72(0.93,3.19) Smoker (yes/no)2.51(1.35,4.66)5.20(3.71,7.28)2.09(1.13, 3.87) Alcohol problems2.52(1.79,3.54)1.92(1.60,2.32)1.14(0.76,1.70) Depression (yes/no)1.74(1.17,2.58)1.23(0.99,1.53)3.10(2.07,4.65) Low social class (vs high) 1.12(0.63,1.96)0.84(0.64,1.10)1.06(0.61,1.85) Female (vs male)0.36(0.25,0.52)0.49(0.41,0.58)0.71(0.50,1.02) Alex Dregan

10. Presented by Descriptive indexes for cognitive measures at 50 years of age in the study population Sample sizeMean(SD) Global cognition 9,38526.94(4.78) Memory index9,59211.98(2.94) Executive functioning index 9,44211.94(2.90) Alex Dregan

11. Presented by Adjusted B for cognitive functioning outcomes at age 50 as a function of illicit drug use patterns Cognitive indexMemory index Executive functioning index Current drug use Any drug0.27(-0.10,0.63)0.14(-0.09,0.37)0.12(-0.12,0.34) High risk 0.49(-0.30,1.37)0.33(-0.16,0.82)0.16(-0.34,0.65) Low risk -0.07(-0.92,0.78)-0.06(-0.59,0.48)0.09(-0.63,0.44) Ever drug use Any drug0.62(0.41,0.83)0.37(0.24,0.50)0.23(0.10,0.37) High risk 0.08(-0.23,0.40)0.13(-0.06,0.33)-0.08(-0.27,0.12) Low risk 0.40(0.04,0.76)0.39(0.16,0.62)0.02(-0.20,0.25) Severity of drug use Never drug dependency0.25(0.10,0.39)0.27(0.12,0.42)0.25(0.10,0.39) Had a drug dependency -0.27(-1.23,0.69)-0.04(-0.70,0.62)-0.17(-0.78,0.43) Length of drug use Both before and at age 42-0.04(-0.50,0.42)0.11(-0.17,0.40)-0.19(-0.48,0.10) Before age 42 only 0.53(0.31,0.74)0.35(0.22,0.49)0.16(0.02,0.29) Alex Dregan

12. Presented by Adjusted B for cognitive functioning outcomes at age 50 as a function of type of illicit drug use Cognitive indexMemory index Executive functioning index Current drug use Cannabis0.28(-0.10,0.41)0.16(-0.10,0.41)0.11(-0.14,0.36) Ecstasy 0.70(-0.61,2.01)0.40(-0.43,1.22)0.14(-0.70,0.97) Cocaine or crack cocaine 0.78(-0.15,1.72)0.46(-0.14,1.05)0.34(-0.26,0.93) Amphetamines 0.50(-0.55,1.71)-0.06(-0.78,0.66)0.48(-0.24,1.20) Ever drug use Cannabis0.69(0.47,0.92)0.40(0.26,0.54)0.28(0.14,0.43) Ecstasy 0.58(-0.08,1.23)0.37(-0.04,0.77)0.15(-0.27,0.56) Cocaine or crack cocaine 0.43(-0.06,0.91)0.36(0.05,0.67)0.01(-0.30,0.32) Amphetamines 0.49(0.11,0.86)0.41(-0.17,0.64)0.07(-0.17,0.30) Heroin-0.02(-0.94,0.90)0.34(-0.24,0.92)-0.43(-1.02,0.16) Alex Dregan

13. Presented by Conclusions - No association between current illicit drug use at age 42 years and cognitive functioning at 10-year follow-up - Ever drug use association with cognitive functioning implies that any cognitive deficits associated with immediate illicit drug use might dissipate with time - The association between past use and cognitive function might be explained by residual confounding (ie higher educational level among ever illicit drug users) - Negative association between drug dependency and long-term illicit drug use and subsequent cognitive functioning Alex Dregan

14. Presented by Conclusions... - Limitations: self-report, baseline cognitive functioning, reverse causality - Exploring the influence of illicit drug use over a longer period of time, we were able to avoid the bias caused by false cognitive impairment - At the population level, it does not appear that past or even current illicit drug use is associated with impaired cognitive functioning in early middle age - The relation between illicit drug use and cognitive impairment is a complex one: possible that some individuals and groups, such as those with heavier or more prolonged use, could be harmed Alex Dregan

15. Presented by Reference - Dregan A, Gulliford MC. Is illicit drug use harmful to cognitive functioning in midadult years?A cohort- based investigation. American Journal of Epidemiology 2012;175(3):218-227. Alex Dregan