Objectives: Over half the US population experiences noise levels above WHO recommendations yet little research within the US has examined the health effects of these exposures. Our objective is to investigate the associations between community noise and blood pressure in residents of Chicago.
Methods: Participants were from two prospective cohort studies: the Multi Ethnic Study of Atherosclerosis (MESA) and the Chicago Health and Aging Project (CHAP). MESA is a multi-site study of persons aged 45-84 years and free of clinical cardiovascular disease. CHAP is an open cohort initiated to study chronic conditions of aging among persons aged ≥65 years. This analysis focuses on the 5,167 participants of these cohorts living in Chicago with an average of 2.5 (CHAP) and 4.5 (MESA) assessments per participant, for systolic (SBP) and diastolic (DBP) blood pressure between 1999-2011. In both cohorts, hypertension was defined as taking antihypertensive medication, SBP ≥140 or DBP ≥ 90 mmHg. We estimated noise at participant addresses using land use regression models weighted according to participants’ 5-year residential history before each exam. Among those taking antihypertensive medication, blood pressure was adjusted using multiple imputation. Associations between noise and blood were estimated using linear mixed models. A Cox proportional hazards model was used to estimate relative risk (RR) of incident hypertension. All models included calendar time, age, sex, race, income, education, neighborhood socioeconomic score, smoking, cohort, interaction between cohort and age, race, and gender, and NOx (a traffic-related air pollutant).
Findings: At baseline, MESA participants were younger (63 vs 73 years) and more educated (36 vs. 3% with ≥graduate degree) than CHAP participants. MESA participants had higher noise levels (60 vs 56 dB) and lower blood pressures (e.g. SBP: 124 vs 135 mmHg) than CHAP participants. After adjusting for cohort and other confounders, we found that 10 dB higher residential noise levels were associated with 0.9 (95% CI: -0.2, 0.2; p=0.1) and 0.5 mmHg greater (95% CI: -0.1, 0.11; p=0.08) SBP and DBP, respectively. Similar associations were found within each cohort. Noise was not associated with incident hypertension overall (RR: 1.00; 95% CI: 0.8, 1.3, p=0.98) or within cohort.
Conclusions: We found a suggestive association between noise and blood pressure levels, but no association with hypertension. This could be due to the lack of nighttime noise information, which has been shown to be more strongly associated with blood pressure outcomes than daytime levels or with the selection of healthy older participants.