TABLE 1

Studies investigating temperature and other climatic variables on sleep apnoea severity

First author [ref.]SettingStudy designParticipantsSubjects nOzoneTemperaturePM10Notes
Weinreich [2]Essen, Bochum and Mulheim, GermanyCross-sectional analysis of a cohort study Adjusted for relative humidity, season, age, sex, BMI, education, smoking, alcohol, physical activity, and CVD and diabetes outcomesCommunity-dwelling adults aged 50–80 years1733↑ (8-h mean) Adjusted for RH, PM10, age, sex and lifestyle↑ Adjusted for RH, PM10, age, sex and lifestyleDaily means (lag 0), moving averages (lag 0, 1 day and lag 0–2 days) City-wide monitors (2–4).
Zanobetti [1]7 US urban areasCross-sectional analysis of a cohort studyCommunity-dwelling adults (aged >39 years) who were members of parent cohorts3030ND↑ (overall, short-term temperature)
Adjusted for season, mean temperature, age, BMI, sex, education, smoking, coffee, tea and alcohol
↑ (summer)
Short-term PM10 (365-day average)
RDI and % time with oxyhaemoglobin desaturation <90% and sleep efficiency − (other seasons or overall)
Several monitors PM10 averaged over locations for each city Daily mean PM10 concentration used in analysis
Cassol [3]Clinical sleep laboratory in Porto Alegre, BrazilRetrospective chart review, January 2000–December 2009Routinely tested sleep apnoea patients7523
Adjusted for sex, age, BMI, neck circumference and RH
RH was a significant predictor in multivariate model
Lags of 1, 2, 3 and 4 days tested for environmental variables
Valham [4]Sleep laboratory in Umea, SwedenExperiment: 3-arm randomised cross-over (3 nights at 16°C, 20°C and 24°C)Untreated mild–moderate sleep apnoea patients (AHI 10–40 events per h)40ND↓ (no data on room humidity) Adjusted for BMI, time in supine position/sleep time and sleep stage on awakeningND
  • Cassol et al. [3] also reported the following associations with OSA: atmospheric pressure (↑), humidity (↑), carbon monoxide levels (↑), precipitation (−) and sulfur dioxide (−). BMI: body mass index; CVD: cardiovascular disease; AHI: apnoea–hypopnoea index; ↑: increased levels increased the severity of sleep apnoea; ↓: increased levels decreased the risk of sleep apnoea; −: increased levels had no effect on sleep apnoea; ND: not determined; RH: relative humidity; PM10: particulate matter less than 10 μm in diameter; RDI: respiratory disturbance index.