Use of Fan During Sleep and the Risk of Sudden Infant Death

Syndrome

De-Kun Li, MD, PhD

Division of Research

Kaiser Permanente

Oakland, California

March 24, 2009

Background

What do we know about SIDS etiology?

Heterogeneity in etiology – diagnosis by exclusion

Underlying Biological

Susceptibility

Underlying Biological

Susceptibility

Brain Stem

Heart Problem

EnvironmentalTriggers

EnvironmentalTriggers

Sleep Environment

AirPollution

SIDS RISK

First 9 months

SIDS RISK WITH AGE

Infections

Brain Stem

Deficiency

Brain Stem

Deficiency

Resuscitation CapabilityResuscitation Capability

ThermoregulationThermoregulation

Prenatal ExposurePrenatal Exposure

GeneticFactors?GeneticFactors?

GestationalDiabetes

GestationalDiabetes

PreeclampsiaPreeclampsia

InfectionInfection

Maternal smokingMaternal smoking

SleepEnvironment

SleepEnvironment

Sleep PositionSleep Position

Pacifier UsePacifier Use

Soft BeddingSoft Bedding

Fan UseFan Use

Bed SharingBed Sharing

Background

Sleep environment matters

Oxygen deprivation

CO2 re-breathing?

Thermal factor?

Other factors?

Objectives

To examine whether use of a fan in the room impacts the risk of SIDS

To examine whether any other factors influence the relationship between use of a fan and the risk of SIDS

To examine whether opening of a window also has a similar effect on the risk of SIDS as use of a fan

Study Design

Population-based case-control study

Study population

All confirmed SIDS cases in 11 counties in California

Infant age-, ethnicity-matched controls in the same county

English or Spanish speaking

Participation rate: 50% in cases and 41% in controls

Study Design

In-person interview

Use of a fan during the last sleep

Sleep positions

Sleep environment (co-sleep, pacifier, etc)

Other risk factors for SIDS

Statistical analysis

Logistic regression to adjust for confounders

Stratification for evaluating interaction

Comparison with birth certificate data to assess participation bias

Table 1. Characteristics of the Study Population

Characteristic

Cases Controls

(n = 185) (n = 312) aOR (95% CI)*

N (%) N (%)

Maternal Characteristics

Race/ Ethnicity

White 59 (31.9) 119 (38.1) 1.00†

Black 34 (18.4) 59 (18.9) 0.96 (0.52, 1.76)

Latino 61 (33.0) 98 (31.4) 1.22 (0.67, 2.19)

Other 31 (16.8) 36 (11.5) 2.23 (1.13, 4.39)

Age (years)

< 20 25 (13.5) 27 (8.7) 1.80 (0.88, 3.70)

20 - 24 55 (29.7) 54 (17.3) 1.86 (1.12, 3.09)

≥ 25 105 (56.8) 231 (74.0) 1.00†

Table 1. Characteristics of the Study Population (Cont.)

Characteristic

Cases Controls

(n = 185) (n = 312) aOR (95% CI)*

N (%) N (%)

Maternal Characteristics (cont.)

Education

≤ 12 113 (61.1) 141 (45.2) 1.31 (0.81, 2.13)

> 12 72 (38.9) 171 (54.8) 1.00†

Marital Status

Married 93 (50.3) 206 (66.0) 1.00†

Cohabiting 61 (33.0) 72 (23.1) 1.49 (0.87, 2.52)

Single 31 (16.8) 34 (10.9) 1.79 (0.93, 3.47)

Region

Northern CA 115 (35.3) 211 (64.7) 1.00†

Southern CA 70 (40.9) 101 (59.1) 1.07 (0.68, 1.68)

Table 1. Characteristics of the Study Population (Cont.)

Characteristic

Cases Controls

(n = 185) (n = 312) aOR (95% CI)*

N (%) N (%)

Maternal Characteristics (cont.)

Parity (Prior To Index Birth)

0 57 (30.81) 132 (42.3) 1.00†

1 69 (37.3) 96 (30.8) 1.51 (0.91, 2.51)

2 32 (17.3) 52 (16.7) 1.46 (0.77,2.80)

≥ 3 27 (14.6) 32 (10.3) 2.16 (1.02, 4.59)

Smoked During Pregnancy

No 137 (74.5) 265 (85.2) 1.00†

Yes 47 (25.4) 46 (14.8) 1.91 (1.14, 3.28)

Wks Gestation at First Prenatal Visit

< 12 120 (65.6) 238 (77.8) 1.00†

≥ 12 63 (34.4) 68 (22.2) 1.59 (1.00, 2.53)

Table 1. Characteristics of the Study Population (Cont.)

Characteristic

Cases Controls

( n = 185) (n = 312) aOR (95% CI)*

N (%) N (%)

Infant Characteristics

Age (Months)

< 2 45 (24.3) 62 (19.9) 1.57 (0.87, 2.81)

2 - 3 90 (48.7) 155 (49.7) 1.08 (0.66, 1.76)

≥ 4 Months 50 (27.0) 95 (30.5) 1.00†

Birth Weight (Grams)

≥ 2500 148 (81.8) 297 (95.5) 1.00†

< 2500 33 (18.2) 14 (4.5) 4.90 (2.34, 10.26)

Infant Health During Previous 48 Hours

No Illness 107 (58.5) 196 (62.8) 1.00†

Sick, No Fever 67 (36.6) 109 (34.9) 1.20 (0.78, 1.85)

Sick with Fever 9 (4.9) 7 (2.2) 2.6 (0.84, 8.03)

Table 1. Characteristics of the Study Population (Cont.)

Characteristic

Cases Controls

(n = 185) (n = 312) aOR (95% CI)*

N (%) N (%)

Infant Characteristics (cont.)

Premature (< 37 Wks Gestation)

No 150 (81.2) 287 (92.0) 1.00†

Yes 35 (18.9) 25 (8.0) 2.96 (1.58, 5.54)

Sleep Environment

Last Sleep Position

On Back 52 (31.1) 175 (56.1) 1.00†

On Stomach or Side 115 (68.9) 137 (43.9) 2.74 (1.79, 4.21)

Used a Pacifier

No 162 (95.9) 236 (76.4) 1.00†

Yes 7 (4.1) 73 (23.6) 0.10 (0.04, 0.23)

Table 1. Characteristics of the Study Population (Cont.)

Characteristic

Cases Controls

(n = 185) (n = 312) aOR (95% CI)*

N (%) N (%)

Sleep Environment (cont.)

Room Temp (°F)

≤ 70 96 (69.1) 176 (61.5) 1.00†

> 70 43 (30.9) 110 (38.5) 0.65 (0.40, 1.06)

Soft Bedding Under Infant

No 125 (76.2) 250 (80.4) 1.00†

Yes 39 (23.8) 61 (19.6) 0.95 (0.57, 1.59)

Soft Sleep Surface

No 153 (87.9) 289 (93.2) 1.00†

Yes 21 (12.1) 21 (6.8) 1.36 (0.68, 2.71)

Covers Over Head

No 147 (88.6) 297 (95.5) 1.00†

Yes 19 (11.5) 14 (4.5) 3.13 (1.40, 7.02)

Table 1. Characteristics of the Study Population (Cont.)

Characteristic

Cases Controls

(n = 185) (n = 312) aOR (95% CI)*

N (%) N (%)

Sleep Environment (cont.)

Bed Sharing Status

Slept Alone 103 (59.9) 195 (67.2) 1.00†

Slept with Parent(s) Only 45 (26.2) 79 (27.2) 1.01 (0.61, 1.68)

Slept with Non-Parent(s)# 24 (14.0) 16 (5.5) 2.86 (1.35, 6.07)

Regular Smoking in Home Postpartum

No 164 (89.1) 291 (94.2) 1.00†

Yes 20 (10.9) 18 (5.8) 1.50 (0.68, 3.31)

*Odds ratio and 95% confidence interval adjusted for race/ethnicity, maternal age, education, region, smoking during pregnancy, infant age, birth year and last sleep position unless the variable itself was the exposure of interest. Maternal race/ethnicity, infant age at last sleep, and region are matching variables.†Reference group#Presence of other individuals (with or without parents)

Table 2. Use of a Fan or having an open window in

Relations to SIDS Risk*

Characteristic

Cases Controls

(n = 185) (n = 312) aOR (95% CI)†

N (%) N (%)

Fan on in Room at Last Sleep

No 161 (96.4) 273 (88.4) 1.00‡

Yes 6 (3.6) 36 (11.7) 0.28 (0.10, 0.77)

Window Open in Room at Last Sleep

No 136 (84.0) 232 (75.1) 1.00‡

Yes 26 (16.1) 77 (24.9) 0.64 (0.33, 1.21)

Table 3. The Effect of Fan Use on SIDS Risk by Sleep

Environment

Characteristic

Cases Controls

(n = 185) (n = 312) aOR (95% CI)†

N (%) N (%)

Room Temperature

Room Temperature ≤ 70° F at Last Sleep

No Fan 91 (94.8) 163 (93.1) 1.00‡

Fan On 5 (5.2) 12 (6.9) 0.77 (0.22, 2.73)

Room Temperature > 70° F at Last Sleep

No Fan 41 (97.6) 88 (80.0) 1.00‡

Fan On 1 (2.4) 22 (20.0) 0.06 (0.01, 0.52)

Table 3. The Effect of Fan Use on SIDS Risk by Sleep

Environment (Cont.)

CharacteristicCases Controls

(n = 185) (n = 312) aOR (95% CI)†

N (%) N (%)

Window Closure

Room with Window Closed at Last Sleep

No Fan 132 (98.5) 211 (91.0) 1.00‡

Fan On 2 (1.5) 21 (9.1) 0.15 (0.03, 0.71)

Room with Window Open at Last Sleep

No Fan 22 (84.6) 62 (80.5) 1.00‡

Fan on 4 (15.4) 15 (19.5) 0.73 (0.17, 3.08)

Placed on Back at Last Sleep

No Fan 48 (94.1) 156 (90.2) 1.00‡

Fan On 3 (5.9) 17 (9.8) 0.84 (0.21, 3.39)

Placed Prone or on Side at Last Sleep

No Fan 108 (97.3) 117 (86.0) 1.00‡

Fan on 3 (2.7) 19 (14.0) 0.14 (0.03, 0.55)

Table 3. The Effect of Fan Use on SIDS Risk by Sleep

Environment (Cont.)

Characteristic

Cases Controls

(n = 185) (n = 312) aOR (95% CI)†

N (%) N (%)

Bed Sharing

Slept Alone at Last Sleep

No Fan 93 (96.9) 169 (86.7) 1.00‡

Fan On 3 (3.1) 26 (13.3) 0.23 (0.06, 0.90)

Slept with Parents only at Last Sleep

No Fan 44 (47.8) 75 (94.9) 1.00‡

Fan On 1 (2.2) 4 (5.1) 0.40 (0.03, 4.68)

Slept with Non-Parents at Last Sleep§

No Fan 22 (95.6) 11 (68.8) 1.00‡

Fan on 1 (4.3) 5 (31.3) 0.15 (0.01, 1.85)

Table 3. The Effect of Fan Use on SIDS Risk by Sleep

Environment (Cont.)

Characteristic

Cases Controls

(n = 185) (n = 312) aOR (95% CI)†

N (%) N (%)

Pacifier Use

Used Pacifier at Last Sleep

No Fan 6 (85.7) 65 (89.0) 1.00‡

Fan On 1 (14.3) 8 (11.0) 1.99 (0.16, 24.4)

No Pacifier Used at Last Sleep

No Fan 153 (96.8) 206 (88.0) 1.00‡

Fan On 5 (3.2) 28 (12.0) 0.22 (0.07, 0.69)

Limitations

Low participation rate

Adjustment for socio-demographic factors

Strong protective effect ---- strong participation bias

Compare to birth certificate data

Recall bias? Adjusting for recall interval

Comparison between Participants and Source Population

Risk Factor

Participants

Cases (n= 179) / Controls (n= 304)

Source Population

All cases (n= 348)/ ethnically matched controls (n = 10010)

OR 95% C.I. OR 95% C.I. Maternal age < 20 years 2.1 1.2-3.6 1.5 1.1-2.0 Mother’s education < 12th grade

1.9

1.3-2.8

1.7

1.4-2.2

Parity > 3 2.6 1.6-4.4 1.8 1.4-2.3 Birth weight < 2500 gms 4.8 2.6-9.1 3.2 2.4-4.2

Male Infant 1.0 0.7-1.4 1.5 1.2-1.8 Gestational age at initial prenatal visit > 5 months

1.5

0.8-2.5

1.6

1.1-2.0

Limitations

Limited information related to fan use• Duration• Location• Type of fan used (ceiling, floor, etc)• Orientation of the fan (facing or away)

Conclusions

Use of fan in the sleeping room may reduce the risk of SIDS

The finding is consistent with other known factors in the sleep environment that influence the SIDS risk

Use of a fan could be another simple and effective way to further reduce SIDS