Exposure to particulate matter air pollution and risk of multiple sclerosis in two large cohorts of US nurses

BACKGROUND

Air pollution is thought to raise the risk of neurological disease by promoting neuroinflammation, oxidative stress, glial activation and cerebrovascular damage. Multiple Sclerosis is a common auto-immune disorder, primarily affecting young women. We conducted, to a large prospective study of particulate matter (PM) exposure and multiple sclerosis (MS) risk in two prospective cohorts of women: the Nurses Health Study (NHS) and the Nurses Health Study II (NHS II).

METHODS

Cumulative average exposure to different size fractions of PM up to the onset of MS was estimated using spatio-temporal models. We used multivariable Cox proportional hazards models to estimate the hazard ratios (HR) and 95% confidence intervals (CI) of MS associated with each size fraction of PM independently. Participants were followed from 1998 through 2004 in NHS and from 1988 through 2007 for NHS II. We conducted additional sensitivity analyses stratified by smoking, region of the US, and age, as well as analyses restricted to women who did not move during the study. Analyses were adjusted for age, ancestry, smoking, body mass index at age 18, region, tract level population density, latitude at age 15, and UV index.

RESULTS

We did not observe significant associations between air pollution and MS risk in our cohorts. Among women in the NHS II, the HRs comparing the top vs. bottom quintiles of PM was 1.11 (95% Confidence Intervals (CI): 0.74, 1.66), 1.04 (95% CI: 0.73, 1.50) and 1.09 (95% CI: 0.73, 1.62) for PM₁₀ (≤10μm in diameter), PM_2.5 (≤2.5μm in diameter), and PM_2.5-10 (2.5 to 10μm in diameter) respectively, and tests for linear trends were not statistically significant. No association between exposure to PM and risk of MS was observed in the NHS.

CONCLUSIONS

In this study, exposure to PM air pollution was not related to MS risk.

Comparison of associations of adherence to a Dietary Approaches to Stop Hypertension (DASH)-style diet with risks of cardiovascular disease and venous thromboembolism

BACKGROUND

Venous thromboembolism (VTE) and cardiovascular disease (CVD) share some risk factors, including obesity, but it is unclear how dietary patterns associated with reduced risk of CVD relate to risk of VTE.

OBJECTIVE

 To compare the relationships of adherence to a Dietary Approaches to Stop Hypertension (DASH)-style diet with the risks of CVD and VTE.

PATIENTS/METHODS

We confirmed by medical record review 1094 incident cases of CVD and 675 incident VTEs during a mean follow-up of 14.6 years in 34 827 initially healthy participants in the Women's Health Study who completed at baseline a 133-item food frequency questionnaire scored for adherence to a DASH diet. We compared estimated associations of dietary patterns with CVD and VTE from proportional hazards models in a competing risk framework.

RESULTS

Initial analyses adjusted for age, energy intake and randomized treatments showed 36-41% reduced hazards of CVD among women in the top two quintiles of DASH score relative to those in the bottom quintile (P(trend) < 0.001). In multivariate analysis, women in the top two quintiles had 12-23% reduced hazards of CVD relative to women in the bottom quintile (P(trend) = 0.04). Analyses restricted to coronary events showed more variable 10-33% reduced hazards in the top two quintiles (P(trend) = 0.09). In contrast, higher DASH scores were unrelated to risk of VTE, with a 1% reduced hazard for the top vs. bottom quintile (P(trend) = 0.95).

CONCLUSION

An apparently strong association of adherence to the DASH diet with incidence of CVD was attenuated upon control for confounding variables. Adherence to the DASH diet was not associated with risk of VTE in women.