Perinatal mortality in Belarus and Ukraine before and after Chernobyl

Alfred Körblein

Munich Environmental InstituteMunich, Germany

Objective of the study

To test perinatal mortality rates in highly contaminated regions of Belarus and Ukraine for a possible association

with the radiation burden of pregnant women

Caesium burden in pregnant women

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86 87 88 89calendar years

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Perinatal mortality in Germany

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80 81 82 83 84 85 86 87 88 89 90 91 92 93

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Perinatal mortality in Poland

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81 82 83 84 85 86 87 88 89 90 91

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Poland

Germany

Perinatal mortality in England and Wales

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81 82 83 84 85 86 87 88 89 90 91 92

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Perinatal mortality in the oblasts of Belarus

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85 86 87 88 89 90 91 92 93 94 95 96 97 98

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Minsk City

Gomel

Mogiliov

Viterbsk

Grodny

Brest

Minsk

Problems with trend analysis:

1. Definition change of stillbirths in 1994

2. Possible influence of socio-economic factors after the break-up of Soviet Union in 1991

Therefore:

Comparison of perinatal motality rates in Gomel to the rates in the rest of Belarus except Minsk City, assuming that other influencing factors act equally in study and control region

Study and control area

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Minsk City

Gomel (study)

Belarus minus Gomel and Minsk City (control)

Odds ratios

odds ratio (OR) = p1/(1-p1) / (p0/(1-p0))

wherep1 mortality rate in study area (Gomel)

p0 mortality rate in control area

for p0, p1 << 1: OR ~ RR = p1/p0 = relative risk

Ratio of mortality rate in Gomel to rate in control area

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85 86 87 88 89 90 91 92 93 94 95 96 97 98

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Increased perinatal mortality in the 1990‘s – a late effect from Chernobyl?

Hypothesis:Increase of perinatal mortality is associated with

strontium burden of pregnant women

Strontium deposition near the Chernobyl site

Strontium retention in a womanas a function of age before and after menarche

from: E.I. Tolstykh et al. Analysis of strontium metabolism in humans on the basisfrom: E.I. Tolstykh et al. Analysis of strontium metabolism in humans on the basis of the Techa river data. Radiat Environ Biophys (1997) 36: 25-29 of the Techa river data. Radiat Environ Biophys (1997) 36: 25-29

Calculation of strontium burden of pregnant women

Approximation:Strontium uptake at age 14 (menarche) and in 1986 only

Average strontium concentration Sr(t) depends on:

1. percentage of pregnant women aged 14 in 1986, i.e. born in 1972: Sr(t) ~ (t-1972),where t is calendar year and A(age) is the maternal age distribution

2. strontium excretion, determined by biological half-life T½:Sr(t) ~ exp(-ln(2)·(t-1986)/ T½)

Maternal age distribution in Belarus

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Regression model

ln(OR) = ln(1+c0+c1·d87+c2·Sr(t))

with d87 = dummy variable for 1987

Sr(t) = calculated strontium concentration in pregnant women

and weights:

σ² = 1/n1 + 1/(N1-n1) + 1/n0 + 1/(N0-n0)

n1, n0 = number of perinatal deathsN1, N0 = number of births

in Gomel (1) and rest of Belarus minus Minsk City (0)

Odds ratios of perinatal mortality(Gomel vs. Belarus minus Gomel and Minsk City)

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Regression results

Comparison of sum of squares obtained in regressions without (red line) and with (blue line) the strontium term.

From the difference of sum of squares, a p-value of p=0.0006

is determined (F-test)

This corresponds to 388 excess perinatal deaths in the observation period

Ukraine

Data:

Monthly data of perinatal mortality, 1985-91,

for three oblasts:

Kiev region, Kiev City, Zhytomyr

Perinatal mortality in Kiev, Kiev City, Zhytomyr

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85 86 87 88 89 90 91 92

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Kiev City

Kiev region

Zhytomyr

Germany

Combined regression model

Linear logistic regression model for perinatal mortality E(Y(t)) + seasonal components + strontium effect Data from 5/1986-12/1988 are omitted (possible caesium influence)

E(Y(t)) =1/(1+1/exp((c1+c4·Sr(t))·city+(c2+c5·Sr(t))·kiev +(c3+c6·Sr(t))·zhytomyr+

c7·t +(c8·cos(2π·(t-c9))·(city+region) +c10·cos(2π·(2t-c11)))·city))

with parametersc1,c2,c3: interceptsc4,c5,c6: strontium terms c7: slopec8 - c11: seasonal components (12 and 6 months period)

city, kiev, zhytomyr are dummy variables identifing the data sets

Regression results for Ukraine

parameter estimate SD t-value p-value c1 -3.7829 0.0339 -111.6770 <0.0001 c2 -4.1316 0.0418 -98.8280 <0.0001 c3 -4.3466 0.0478 -90.8500 <0.0001 c4 0.0328 0.0468 0.7010 0.4843

c5 0.1312 0.0495 2.6480 0.0089

c6 0.3122 0.0490 6.3760 <0.0001

c7 -0.0657 0.0137 -4.7930 <0.0001 c8 0.0713 0.0223 3.2010 0.0016 c9 0.0399 0.0502 0.7950 0.4277 c10 0.0614 0.0276 2.2190 0.0278 c11 0.6514 0.0730 8.9280 <0.0001

Kiev CityKiev regionZhytomyr

Kiev City

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Kiev City

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Kiev region

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Kiev region

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Zhytomyr

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Zhytomyr

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Infant mortality in Poland

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Conclusion

• Perinatal mortality in Gomel is associated with strontium burden in pregnant women

• Strontium effect on perinatal mortality in Ukraine is greater in Zhytomyr than in Kiev region and is not significant in Kiev City

• Perinatal mortality in Zhytomyr exhibits a peak in the beginning of 1987 which is associated with the caesium burden in pregnant women

Thank you for your attention!