The research, published in Plos One, studied 3,568 members of the Amish community in Lancaster County in Pennsylvania (USA) between 2001 and 2015. Men accounted for 43% of the group.
In total, 34% of men in the study said that they had ever smoked, of which 46% reported current smoking, compared with less than 1% of women.
Researchers at the University of Maryland School of Medicine (UM SOM) asked participants about their own personal smoking habits -- most commonly the cigar (64%) followed by the cigarette (46%) then the pipe (21%). Since the researchers knew exactly how all the Amish were related to each other, they were able to look at the family tree and extrapolate who had been exposed to secondhand smoke.
Unsurprisingly, the impact of passive smoking was more intense in people with more smokers in their families, including spouses, parents and siblings.
Secondhand smoke was was associated with higher BMI and higher fasting glucose in men, suggesting a diabetes risk, but not in women. Reduced HDL cholesterol ("good cholesterol") was seen only in women exposed to secondhand smoke. Secondhand smoke was associated with a lower heart rate in men only.
The researchers say that cigars and pipes, which are predominant forms of tobacco use in the Amish community, also produce more noxious secondhand smoke than cigarettes.
Tobacco smoking is the leading preventable cause of death in the United States, responsible for an estimated 480,320 deaths annually, including 41,280 deaths attributable to lung cancer and coronary heart disease related to secondhand smoke exposure, according to a 2014 report from the Office of the Surgeon General.
The Amish community is a religious community that favors traditional lifestyles. They have their own schools, speak a specific German dialect, wear traditional clothing, travel by horse and cart, and many refuse to use electricity. There are around 280,000 Amish in the USA.
The study is available here: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0174354