Greenness and job-related chronic stress in young adults: a prospective cohort study in Germany

Abstract

Objectives: We aimed to prospectively study the association between normalised difference vegetation index (NDVI) as a measure of greenness around homes and occupational stress.

Setting: A population-based cohort in Munich and Dresden cities was followed from age 16-18 years to age 20-23 years (n=1632).

Participants: At baseline, all participants attended high-school while at follow-up some had started working and others studying at university. At baseline and in each follow-up, we assigned NDVI based on participants' residential geocoded addresses and categorised it by quartiles.

Outcome measures: School-related, university-related or job-related self-reported chronic stress was assessed at the two follow-ups by the Trier Scale for Assessment of Chronic Stress using work discontent and work overload as outcomes. We modelled the association employing ordinal generalised estimating equations model accounting for changes in sociodemographics, non-job-related stress, job history and environmental covariates. Stratified analysis by each city was performed.

Results: NVDI at baseline was higher for participants from Dresden (median=0.36; IQR 0.31-0.41) than Munich (0.31; 0.26-0.34). At follow-up, it decreased only for participants in Dresden (0.34; 0.30-0.40). Higher greenness (quartile 4 vs quartile 1) was associated with less work discontent (OR 0.89; 95% CI 0.80 to 0.99) and less work overload (OR 0.87; 95% CI 0.78 to 0.96). In stratified analyses, results were more consistent for Munich than for Dresden.

Conclusions: Our results suggest that residential green spaces, using the vegetation index as a proxy for exposure, are inversely associated with two types of job-related chronic stress in German young adults transitioning from school to university or working life.

Keywords: generalized estimation equations; greenness; job stress; multiple imputation; ndvi; prospective study.

Figure 1

Flow chart of follow-up from International Study on Asthma and Allergies in Childhood (ISAAC) phase II to SOLAR II including normalised difference vegetation index (NDVI) measurements, job-related and non-job-related stress variables and total participants in each follow-up and the current analysis. Excluded participants: n=318 ever worked previously to SOLAR I, n=21 no educational status information, n=24 more than two Trier Scale for Assessment of Chronic Stress (TICS) items missing and n=56 residence out of the study areas.

Figure 2

City-specific associations between greenness in a 500 m buffer and work discontent and work overload. Ordinal generalised estimating equation models adjusted for sex, having children, physical activity, education, current status, type of job, psychological variables and environmental variables using complete cases in selected subpopulations: (A) complete cases for the combined population (n=1430), Munich (n=779) and Dresden (n=651). (B) Complete cases that never moved in the combined population (n=629), Munich (n=443) and Dresden (n=186). NDVI, normalised difference vegetation index; Q, quartile.

Figure 3

City-specific associations between greenness in a 500 m buffer and work discontent and work overload. Ordinal generalised estimating equation models adjusted for sex, having children, physical activity, education, current status, type of job, psychological variables and environmental variables using complete cases in selected subpopulations: (A) complete cases students only for the combined population (n=845), Munich (n=463) and Dresden (n=382). (B) Complete cases workers only in the combined population (n=670), Munich (n=359) and Dresden (n=311). NDVI,  normalised difference vegetation index; Q, quartile.