Indoor Green Determinants: Outdoor Green and Other Home Characteristics

Abstract

Background/Aim: Indoor green has been hypothesized to benefit human health and well-being similarly to residential green, which will likely be investigated in future studies. In this Germany-based study, we examined which home characteristics are associated with greater amount of indoor green and whether indoor and outdoor green are interrelated. Methods: Plants units’ number in a living room and a bedroom together with other home characteristics were collected within the INGA study which included 454 children homes from Zerbst, Bitterfeld anf Hettstedt and 437 adult homes from Erfurt and Hamburg. Outdoor green was defined as the mean Normalized Difference Vegetation Index in 50- to 1000-m circular buffers around residences and was available for Erfurt only. Negative binomial regressions were employed to assess the association between indoor green and potential predictor factors, separately for children’s and adult’s homes. Results: Besides area differences in indoor green, size of the apartment was strongest related to a number of plants indoors in both children’s (count ratio: 1.06 [95% confidence intervals; 1.03, 1.09] per 10 m²) and adults’ (1.08 [1.03, 1.13]) homes. Also in children’s homes, newer houses, absence of mice and presence of mould or dampness were related to more plants units. In adults, indoor-green related factors were presence of a dog and a cat as well as fewer rooms in the apartment. Less green in visible neighbourhood (50- and 100-m buffers) was related to having more indoor plants (e.g. 0.71 [0.56, 0.92] in highest tertile of outdoor green compared to lowest tertile). However, for walkable neighbourhood (500- and 1000-m buffers), these associations were in opposite direction. Conclusions: Future research on indoor green should preferably use number of plants per size of the apartment and also cautiously check for potential confounding by other co-factors.