Please read the following abstract and review the methods section of the publication by Wang et al. 2022 and answer the following questions.

Wang TW, Wuu J, Cooley A, Yeh TS, Benatar M, Weisskopf M. Occupational lead exposure and survival with amyotrophic lateral sclerosis. Amyotroph Lateral Scler Frontotemporal Degener. 2022 Apr 9:1-8. doi: 10.1080/21678421.2022.2059379.

Objective: Lead exposure has been hypothesized to increase the risk of ALS, but only two studies have examined the association with ALS survival, and with inconsistent results. The use of occupational history to assess lead exposure can avoid reverse causation that may occur in epidemiologic analyses that use biomarkers of lead exposure collected after ALS onset.

Methods: We evaluated the relationship of occupational lead exposure to ALS survival among 135 cases from an international ALS cohort that included deep phenotyping, careful follow-up, and questionnaires to quantify participants' occupation history. ALS patients were recruited in 2015-2019. We determined occupational lead exposure using a job-exposure matrix. We estimated hazard ratios (HR) and 95% confidence intervals (CI) for survival using Cox proportional hazard analysis with adjustment for covariates.

Results: A total of 135 ALS patients completed the environmental questionnaires, among whom 38 reached a survival endpoint (death or permanent assisted ventilation). The median survival was 48.3 months (25th-75th percentile, 30.9-74.1). Older patients and those with initial symptom other than limb onset had shorter survival time. There were 36 ALS cases with occupational lead exposure. After adjusting for age, sex, site of onset, smoking, and military service, lead exposure was associated with an HR of 3.26 (95%CI 1.28-8.28). Results with adjustment for subsets of these covariates were similar.Conclusions: These results suggest that lead exposure prior to onset of ALS is associated with shorter survival following onset of ALS, and this association is independent of other prognostic factors.

1. What is the unit of observation in the Wang et al 2022 publication? Please select one.
   1. Individual
   2. Group

1. Which best characterizes the study?
   1. Individuals measured at one point in time
   2. Individuals surveyed at two different time periods
   3. Individuals followed over time

1. Based on study designs you've learned to date, which type of study design best describes the Wang et al. 2022 publication?
   1. Individual Cross-sectional
   2. Repeated Cross-sectional
   3. Cohort
   4. Case Series
   5. Case Control
   6. Ecologic Cross-sectional
   7. Ecologic (Repeated)
   8. Randomized Control Trial
   9. Intervention, (not randomized)