PMID- 11018421
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20191120
IS  - 1873-2585 (Electronic)
IS  - 1047-2797 (Linking)
VI  - 10
IP  - 7
DP  - 2000 Oct 1
TI  - The effect of imputation of exposure estimates on the association between fine 
      particulate matter and mortality.
PG  - 477-478
AB  - PURPOSE: The Harvard Six Cities Study (HSCS) found a small but significant 
      association between daily PM2.5 and daily mortality count. The HSCS findings have 
      been used as the basis for new EPA regulations, requiring lower levels of PM2.5. 
      We feel that there are unresolved issues regarding the HSCS that should be fully 
      evaluated prior to its findings being used as the basis of new regulation, 
      including how the extent and method of imputing exposure data affect the 
      association with daily mortality counts.METHODS: We examined the association 
      between PM2.5 levels and daily mortality count, comparing the results from the 
      HSCS methods with results based on an alternate imputation method, and with 
      non-missing data.RESULTS: Overall, approximately 30% of the data points used in 
      the HSCS were imputed. The method of imputation affected the association between 
      particulate matter and mortality to a substantial degree in most of the cities. 
      When the model using the HSCS method was compared to the model using the 
      alternate method, in two areas the coefficients decreased substantially and lost 
      significance. In two areas they changed little; in one area it rose substantially 
      and became significant; and in one area it declined substantially but remained 
      significant. When compared to the model based on the non-missing data, somewhat 
      different patterns were observed. In both comparisons there were some large 
      changes in the magnitude of the effect, but these were not consistent with the 
      model used.CONCLUSIONS: We are concerned about the degree of data imputation and 
      the effect that the method of imputation has on the association between 
      particulate matter levels and mortality. In the case of the HSCS it appears that 
      the imputed data are more strongly associated with the outcome than other methods 
      of imputation and than the non-missing data. The reasons for these observations 
      are not readily apparent, but the differences in effect should be explored and 
      explained.
FAU - Klemm, R
AU  - Klemm R
AD  - Klemm Analysis Group, Inc., Washington, DC, USA
FAU - Mason, R
AU  - Mason R
FAU - Heilig, C
AU  - Heilig C
FAU - Cowan, D
AU  - Cowan D
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Ann Epidemiol
JT  - Annals of epidemiology
JID - 9100013
EDAT- 2000/10/06 00:00
MHDA- 2000/10/06 00:01
CRDT- 2000/10/06 00:00
PHST- 2000/10/06 00:00 [pubmed]
PHST- 2000/10/06 00:01 [medline]
PHST- 2000/10/06 00:00 [entrez]
AID - S1047-2797(00)00151-4 [pii]
AID - 10.1016/s1047-2797(00)00151-4 [doi]
PST - ppublish
SO  - Ann Epidemiol. 2000 Oct 1;10(7):477-478. doi: 10.1016/s1047-2797(00)00151-4.