**6. Associative relationships of microclimate and mental health**

#### **6.1 Stress score**

The variable 'stress score' is generated by the smartwatches and is derived from oxygen saturation and heart rate. **Figure 7** shows the Shapley Summary Plot of the associations of microclimate with this variable.

*The Life2 Well Project: Investigating the Relationship between Physiological Stress… DOI: http://dx.doi.org/10.5772/intechopen.107493*

#### **Figure 6.**

*Shapley summary plot of microclimatic factors and self-reported physical state.*

From **Figure 7**, the variable 'stress score' is most strongly associated with the variable 'infrared radiation' (feature importance of 0.363), followed by the variable 'carbon dioxide concentration' (feature importance of 0.226) and by the variable 'ambient temperature' (feature importance of 0.104). The higher the infrared radiation, the higher the stress level. As for carbon dioxide concentration, the higher the concentration, the higher the stress level is. For ambient temperature, the lower the temperature, the lower the stress level is.

#### **6.2 Self-reported mental state**

**Figure 8** shows the Shapley Summary Plot of the associations of microclimate with the variable 'self-reported mental state'.

#### **Figure 7.**

*Shapley summary plot of microclimatic factors and stress score.*

From **Figure 8**, the variable 'self-reported mental state' is most strongly associated with the variable 'sound' (feature importance of 0.18), followed by the variable 'carbon dioxide concentration' (feature importance of 0.17) and by the variable 'dust concentration' (feature importance of 0.13). From the above Shapley Summary Plot, the higher level of sound is, the higher the value of self-reported mental state. Similarly, as carbon dioxide concentration increases, self-reported mental state increases. Finally, self-reported mental state value decreases as dust concentration increases.
