Alternative adjustment for seasonality and long-term time-trend in time-series analysis for long-term environmental exposures and disease counts

Table 3 Percentage increase and 95% confidence intervals of all-cause mortality risk per a 10 μg/m³ Increase in two-day moving average of PM₁₀ (lag0–1) or one-year distributed lags of PM₁₀ (lag0–365) in seven major cities of South Korea, 2006–2013

Adjustment method for seasonality and long-term time-trend^a	Two-day moving average (lag0–1)				One-year distributed lags
	lag2–365 not adjusted		lag2–365 adjusted		(lag0–365)
	PI	95% CI	PI	95% CI	PI	95% CI
Not adjusted	−0.44	−0.71, − 0.16	0.08	−0.08, 0.24	−9.46	−13.27, − 5.48
NCS(t,7df/year)	0.16	0, 0.31	0.12	−0.06, 0.31	4.67	−51.66, 126.62
NCS(t,10df/year)	0.15	−0.01, 0.31	0.14	−0.06, 0.34	−20.60	−76.83, 172.13
NCS(t,12df/year)	0.15	−0.01, 0.31	0.20	−0.01, 0.40	−35.64	−84.39, 165.33
NCS(doy, 20df)+I(year)	0.13	−0.03, 0.28	0.17	0, 0.33	2.86	−2.13, 8.10
10,3,3	0.10	−0.05, 0.26	0.14	−0.05, 0.34	4.40	−0.10, 9.11
20,3,3	0.12	−0.04, 0.27	0.14	−0.03, 0.31	4.66	0.14, 9.38
30,3,3	0.12	−0.04, 0.28	0.15	−0.02, 0.32	4.64	0.07, 9.41
20,4,4	0.12	−0.03, 0.28	0.14	−0.03, 0.31	5.54	1.32, 9.95
20,5,5	0.11	−0.04, 0.27	0.12	−0.05, 0.29	4.55	−0.93, 10.34
20,6,6	0.08	−0.08, 0.24	0.09	−0.09, 0.28	0.50	−5.75, 7.18
20,10,10	0.08	−0.08, 0.23	0.12	−0.09, 0.34	5.45	−4.81, 16.83
20,15,15	0.09	−0.07, 0.25	0.13	−0.07, 0.34	−4.72	−22.75, 17.51

Abbreviations: CI confidence interval, df degrees of freedom, doy day of the year, I(year) an indicator function of year throughout the study period, NCS natural cubic spline, NCS(doy,pdf) NCS of doy with pdf, NCS(t,pdf/year) NCS of time throughout the study period with pdf per year, PI percentage increase, PM₁₀ particulate matter with aerodynamic diameter ≤10 μm
^aNCS(doy,pdf)+I(year)+NCS(week,qdf)+NCS(month,rdf) is described as p,q,r; NCS(week,qdf) is NCS of the order of week throughout the study period with qdf; NCS(month,rdf) is NCS of the order of month throughout the study period with rdf

ISSN: 1471-2288