Stress at work means more illness in older age, according to a new study from Finland. The study found both physical and mental job strain were tied to hospital stays later in life, Fox News reports.

Mental job strain can come from tight deadlines and high demands. Physical strain includes sweating, breathlessness and muscle strain.

Recent studies have linked long-term job strain to lower functioning that lasts into old age, said lead researcher Mikaela von Bonsdorff. She is a gerontology researcher at the University of Jyväskylä in Finland.

The new findings come from a study of more than 5,000 middle-aged Finnish public sector employees who were initially surveyed about stress at work in 1981.

The researchers combined that information with data from national hospital records spanning the next 28 years.

With higher strain in midlife, days in the hospital tended to increase.

For both men and women, hospital days increased as physical strain increased. But for mental strain, the link was only clear among men.

"Job strain of some sort can occur in basically any type of employment," Loretta Platts told Reuters Health.

Platts is a doctoral candidate at Imperial College London. She studies how various factors influence quality of life after retirement and was not involved in the new research.

Mental strain has been linked to heart disease, another cause of hospital stays. Still, the study can't prove that job strain causes poor health and more hospital stays, Platts pointed out.

It's possible that 28 years later, the people spending the most time in hospitals happened to think more negatively about their work in 1981, she said.