Of the 4350 participants included in this analysis, 288 (7%) reported having been incarcerated during the three year period of young adulthood captured in the first two surveys. Black men and less educated participants were most likely to have history of prior incarceration (). Within these subgroups, former inmates were more likely to report family earnings below 200% of the federal poverty line, smoking, illicit drug use, and excess alcohol consumption compared to those without incarceration history.
Sociodemographic and clinical characteristics of 4350 black and white men and women by history of incarceration before 1987
By the year 5 examination, persons with incarceration history had higher mean systolic blood pressures and were more likely to have hypertension (). Among participants without hypertension at baseline, former inmates were more likely to have developed incident hypertension by the year 5 examination (12% vs. 7%, unadjusted odds ratio (OR) 1.7, 95% confidence interval (CI) 1.2, 2.6). Among black men and less educated individuals, subgroups of the CARDIA sample where incarceration was more common, the relationship between incarceration and hypertension was particularly pronounced and statistically significant. Cholesterol levels (LDL, 108 mg/dL: vs. 108 mg/dL, p=0.9; HDL, 53 mg/dL vs. 53 mg/dL p=0.5) and diabetes (2% vs. 3%, p=0.7) did not differ between participants with and without a history of incarceration, even in subgroup analyses.
Blood pressure and hypertension among CARDIA cohort in 1990–91 at age 23–35, by history of incarceration before 1987
Because of the association of incarceration with hypertension, we examined several potential explanatory factors for the observed association of prior incarceration and incident hypertension. Adjustment for age, sex race, drugs and alcohol use did not alter this association (AOR 1.6 95% CI 1.0, 2.5), nor did additional adjustment for poverty (AOR 1.6, 95% CI 1.0, 2.6). Although the statistical tests for interaction between incarceration and race, sex, and education were not significant we ran these models within the sampling strata of CARDIA (). Subgroups with the highest rate of incarceration – black men and less educated participants –showed significant associations between incarceration and incident hypertension in adjusted models; associations in subgroups that had lower rates of incarceration were not significant, but had wide confidence intervals. Although black men and less educated individuals were more likely to have been lost to follow up by year 5, our results were no different in analyses using inverse probability weights to reduce bias due to differential dropout (all participants AOR 1.5, 95% CI 0.9–2.2; black men AOR 1.9, 95% CI 1.0–3.6; less educated participants AOR 1.6, 95% CI 0.9–2.7).
Association of incarceration history before 1987 with subsequent incident hypertension (1990–91) at age 23–35
We examined whether incarceration might be associated with end organ damage related to hypertension. Persons with incarceration history had higher mean left ventricular mass index (54.0 ±14.1 gm/m2 vs. 50.3 ±14.1 gm/m2, p<0.001) and were more likely to have left ventricular hypertrophy (2% vs. 0.6%, p=0.005). Prior incarceration was associated with left ventricular hypertrophy in unadjusted analyses, and we observed a trend for an association even after accounting for potential confounders (). In analyses restricted to black men and less educated individuals, prior incarceration was also associated with left ventricular hypertrophy in both unadjusted and adjusted models.
Association of incarceration history with subsequent access to care at among the 650 CARDIA participants with hypertension
Among participants with hypertension at the year 5 exam, those with a history of incarceration had an increased odds of reporting a barrier to healthcare at the next follow-up visit two years later (Table 5). This association persisted after adjustment for age, race, sex, and socioeconomic status and was more pronounced in black males and less educated participants. Former inmates were also more likely to lack treatment for their hypertension at the Year 7 exam (17% vs. 41%, unadjusted OR 3.3, 95% CI 1.3, 9), and in each of the follow-up visits over the entire 20 year duration of the CARDIA study (unadjusted OR 2.0, 95% CI 1.3, 3.0 at year 20). Incarceration prior to 1987 was associated with a 5.7 mmHg higher mean systolic blood pressure at the Year 20 examination (95% CI: 0.2–11.2), but not a higher diastolic blood pressure at Year 20 (1.1 mmHg (95% CI −0.6, 2.8) in analyses adjusting for the age, sex, and race of these participants.