. 2016 Oct 18;15:98. doi: 10.1186/s12940-016-0179-z

Table 4.

Non-chemical triggers and COPD exacerbation (Weather, flu, and physical activity)

Variable type	Variable description	Odds ratio	95 % confidence interval		−2loglikelihood
Weather	Spent time in cold air/cold weather in past week^a	1.16	0.78	1.70	468
	Spent time in hot air/hot weather in past week^a	0.50	0.34	0.75	457
	Local Temperature (linear 7 day average)^b	0.96	0.95	0.98	445
	Local Temperature (categorical)^c
	Cool/Cold	1.0	1.0	1.0	422
	Moderate	2.50	1.51	4.12
	Warm/Hot	0.55	0.36	0.84
	Local Relative Humidity (linear 7 day average)^b	0.98	0.96	1.01	471
	Local Relative Humidity (categorical)^c
	High	1.0	1.0	1.0	471
	Low	1.21	0.84	1.73	471
Season	Season, ref = summer
	Summer	1.0	1.0	1.0	417
	Spring	2.59	1.55	4.35
	Winter	2.38	1.37	4.11
	Fall	6.64	3.83	11.5
Acute Illness	Respiratory infection/cold in past week^a	8.14	4.67	14.2	396
	Non-respiratory Illness in past week^a	1.65	0.67	4.05	422
	Sinus infection in past week^a	2.55	1.20	5.44	461
	Regional Flu Trends; New England^d	3.78	1.54	9.28	463
Physical Activity	Total hours spent outside of the home^{a, e}	0.99	0.99	1.00	469
Physical Activity	Exercised in past week^a	0.60	0.39	0.93	462

^aBased on self-reports from exposure questionnaires

^bBased on 7-day averages using data from NOAA collected at Worcester Regional Airport

^cCategorical representation of variable based on cut-offs identified in restricted cubic splines

^dRegional proxy of flu from CDC data; represented by percent of weekly outpatient visits for influenza-like-illness in New England

^eEstimated as sum of “Hours Reported Outdoors”, “Hours Reported in a Vehicle”, and “Hours Reported Indoors but not at home”